path: root/contrib/python/Jinja2/py2/jinja2/compiler.py

# -*- coding: utf-8 -*-
"""Compiles nodes from the parser into Python code."""
from collections import namedtuple
from functools import update_wrapper
from itertools import chain
from keyword import iskeyword as is_python_keyword

from markupsafe import escape
from markupsafe import Markup

from . import nodes
from ._compat import imap
from ._compat import iteritems
from ._compat import izip
from ._compat import NativeStringIO
from ._compat import range_type
from ._compat import string_types
from ._compat import text_type
from .exceptions import TemplateAssertionError
from .idtracking import Symbols
from .idtracking import VAR_LOAD_ALIAS
from .idtracking import VAR_LOAD_PARAMETER
from .idtracking import VAR_LOAD_RESOLVE
from .idtracking import VAR_LOAD_UNDEFINED
from .nodes import EvalContext
from .optimizer import Optimizer
from .utils import concat
from .visitor import NodeVisitor

operators = {
    "eq": "==",
    "ne": "!=",
    "gt": ">",
    "gteq": ">=",
    "lt": "<",
    "lteq": "<=",
    "in": "in",
    "notin": "not in",
}

# what method to iterate over items do we want to use for dict iteration
# in generated code?  on 2.x let's go with iteritems, on 3.x with items
if hasattr(dict, "iteritems"):
    dict_item_iter = "iteritems"
else:
    dict_item_iter = "items"

code_features = ["division"]

# does this python version support generator stops? (PEP 0479)
try:
    exec("from __future__ import generator_stop")
    code_features.append("generator_stop")
except SyntaxError:
    pass

# does this python version support yield from?
try:
    exec("def f(): yield from x()")
except SyntaxError:
    supports_yield_from = False
else:
    supports_yield_from = True


def optimizeconst(f):
    def new_func(self, node, frame, **kwargs):
        # Only optimize if the frame is not volatile
        if self.optimized and not frame.eval_ctx.volatile:
            new_node = self.optimizer.visit(node, frame.eval_ctx)
            if new_node != node:
                return self.visit(new_node, frame)
        return f(self, node, frame, **kwargs)

    return update_wrapper(new_func, f)


def generate(
    node, environment, name, filename, stream=None, defer_init=False, optimized=True
):
    """Generate the python source for a node tree."""
    if not isinstance(node, nodes.Template):
        raise TypeError("Can't compile non template nodes")
    generator = environment.code_generator_class(
        environment, name, filename, stream, defer_init, optimized
    )
    generator.visit(node)
    if stream is None:
        return generator.stream.getvalue()


def has_safe_repr(value):
    """Does the node have a safe representation?"""
    if value is None or value is NotImplemented or value is Ellipsis:
        return True
    if type(value) in (bool, int, float, complex, range_type, Markup) + string_types:
        return True
    if type(value) in (tuple, list, set, frozenset):
        for item in value:
            if not has_safe_repr(item):
                return False
        return True
    elif type(value) is dict:
        for key, value in iteritems(value):
            if not has_safe_repr(key):
                return False
            if not has_safe_repr(value):
                return False
        return True
    return False


def find_undeclared(nodes, names):
    """Check if the names passed are accessed undeclared.  The return value
    is a set of all the undeclared names from the sequence of names found.
    """
    visitor = UndeclaredNameVisitor(names)
    try:
        for node in nodes:
            visitor.visit(node)
    except VisitorExit:
        pass
    return visitor.undeclared


class MacroRef(object):
    def __init__(self, node):
        self.node = node
        self.accesses_caller = False
        self.accesses_kwargs = False
        self.accesses_varargs = False


class Frame(object):
    """Holds compile time information for us."""

    def __init__(self, eval_ctx, parent=None, level=None):
        self.eval_ctx = eval_ctx
        self.symbols = Symbols(parent and parent.symbols or None, level=level)

        # a toplevel frame is the root + soft frames such as if conditions.
        self.toplevel = False

        # the root frame is basically just the outermost frame, so no if
        # conditions.  This information is used to optimize inheritance
        # situations.
        self.rootlevel = False

        # in some dynamic inheritance situations the compiler needs to add
        # write tests around output statements.
        self.require_output_check = parent and parent.require_output_check

        # inside some tags we are using a buffer rather than yield statements.
        # this for example affects {% filter %} or {% macro %}.  If a frame
        # is buffered this variable points to the name of the list used as
        # buffer.
        self.buffer = None

        # the name of the block we're in, otherwise None.
        self.block = parent and parent.block or None

        # the parent of this frame
        self.parent = parent

        if parent is not None:
            self.buffer = parent.buffer

    def copy(self):
        """Create a copy of the current one."""
        rv = object.__new__(self.__class__)
        rv.__dict__.update(self.__dict__)
        rv.symbols = self.symbols.copy()
        return rv

    def inner(self, isolated=False):
        """Return an inner frame."""
        if isolated:
            return Frame(self.eval_ctx, level=self.symbols.level + 1)
        return Frame(self.eval_ctx, self)

    def soft(self):
        """Return a soft frame.  A soft frame may not be modified as
        standalone thing as it shares the resources with the frame it
        was created of, but it's not a rootlevel frame any longer.

        This is only used to implement if-statements.
        """
        rv = self.copy()
        rv.rootlevel = False
        return rv

    __copy__ = copy


class VisitorExit(RuntimeError):
    """Exception used by the `UndeclaredNameVisitor` to signal a stop."""


class DependencyFinderVisitor(NodeVisitor):
    """A visitor that collects filter and test calls."""

    def __init__(self):
        self.filters = set()
        self.tests = set()

    def visit_Filter(self, node):
        self.generic_visit(node)
        self.filters.add(node.name)

    def visit_Test(self, node):
        self.generic_visit(node)
        self.tests.add(node.name)

    def visit_Block(self, node):
        """Stop visiting at blocks."""


class UndeclaredNameVisitor(NodeVisitor):
    """A visitor that checks if a name is accessed without being
    declared.  This is different from the frame visitor as it will
    not stop at closure frames.
    """

    def __init__(self, names):
        self.names = set(names)
        self.undeclared = set()

    def visit_Name(self, node):
        if node.ctx == "load" and node.name in self.names:
            self.undeclared.add(node.name)
            if self.undeclared == self.names:
                raise VisitorExit()
        else:
            self.names.discard(node.name)

    def visit_Block(self, node):
        """Stop visiting a blocks."""


class CompilerExit(Exception):
    """Raised if the compiler encountered a situation where it just
    doesn't make sense to further process the code.  Any block that
    raises such an exception is not further processed.
    """


class CodeGenerator(NodeVisitor):
    def __init__(
        self, environment, name, filename, stream=None, defer_init=False, optimized=True
    ):
        if stream is None:
            stream = NativeStringIO()
        self.environment = environment
        self.name = name
        self.filename = filename
        self.stream = stream
        self.created_block_context = False
        self.defer_init = defer_init
        self.optimized = optimized
        if optimized:
            self.optimizer = Optimizer(environment)

        # aliases for imports
        self.import_aliases = {}

        # a registry for all blocks.  Because blocks are moved out
        # into the global python scope they are registered here
        self.blocks = {}

        # the number of extends statements so far
        self.extends_so_far = 0

        # some templates have a rootlevel extends.  In this case we
        # can safely assume that we're a child template and do some
        # more optimizations.
        self.has_known_extends = False

        # the current line number
        self.code_lineno = 1

        # registry of all filters and tests (global, not block local)
        self.tests = {}
        self.filters = {}

        # the debug information
        self.debug_info = []
        self._write_debug_info = None

        # the number of new lines before the next write()
        self._new_lines = 0

        # the line number of the last written statement
        self._last_line = 0

        # true if nothing was written so far.
        self._first_write = True

        # used by the `temporary_identifier` method to get new
        # unique, temporary identifier
        self._last_identifier = 0

        # the current indentation
        self._indentation = 0

        # Tracks toplevel assignments
        self._assign_stack = []

        # Tracks parameter definition blocks
        self._param_def_block = []

        # Tracks the current context.
        self._context_reference_stack = ["context"]

    # -- Various compilation helpers

    def fail(self, msg, lineno):
        """Fail with a :exc:`TemplateAssertionError`."""
        raise TemplateAssertionError(msg, lineno, self.name, self.filename)

    def temporary_identifier(self):
        """Get a new unique identifier."""
        self._last_identifier += 1
        return "t_%d" % self._last_identifier

    def buffer(self, frame):
        """Enable buffering for the frame from that point onwards."""
        frame.buffer = self.temporary_identifier()
        self.writeline("%s = []" % frame.buffer)

    def return_buffer_contents(self, frame, force_unescaped=False):
        """Return the buffer contents of the frame."""
        if not force_unescaped:
            if frame.eval_ctx.volatile:
                self.writeline("if context.eval_ctx.autoescape:")
                self.indent()
                self.writeline("return Markup(concat(%s))" % frame.buffer)
                self.outdent()
                self.writeline("else:")
                self.indent()
                self.writeline("return concat(%s)" % frame.buffer)
                self.outdent()
                return
            elif frame.eval_ctx.autoescape:
                self.writeline("return Markup(concat(%s))" % frame.buffer)
                return
        self.writeline("return concat(%s)" % frame.buffer)

    def indent(self):
        """Indent by one."""
        self._indentation += 1

    def outdent(self, step=1):
        """Outdent by step."""
        self._indentation -= step

    def start_write(self, frame, node=None):
        """Yield or write into the frame buffer."""
        if frame.buffer is None:
            self.writeline("yield ", node)
        else:
            self.writeline("%s.append(" % frame.buffer, node)

    def end_write(self, frame):
        """End the writing process started by `start_write`."""
        if frame.buffer is not None:
            self.write(")")

    def simple_write(self, s, frame, node=None):
        """Simple shortcut for start_write + write + end_write."""
        self.start_write(frame, node)
        self.write(s)
        self.end_write(frame)

    def blockvisit(self, nodes, frame):
        """Visit a list of nodes as block in a frame.  If the current frame
        is no buffer a dummy ``if 0: yield None`` is written automatically.
        """
        try:
            self.writeline("pass")
            for node in nodes:
                self.visit(node, frame)
        except CompilerExit:
            pass

    def write(self, x):
        """Write a string into the output stream."""
        if self._new_lines:
            if not self._first_write:
                self.stream.write("\n" * self._new_lines)
                self.code_lineno += self._new_lines
                if self._write_debug_info is not None:
                    self.debug_info.append((self._write_debug_info, self.code_lineno))
                    self._write_debug_info = None
            self._first_write = False
            self.stream.write("    " * self._indentation)
            self._new_lines = 0
        self.stream.write(x)

    def writeline(self, x, node=None, extra=0):
        """Combination of newline and write."""
        self.newline(node, extra)
        self.write(x)

    def newline(self, node=None, extra=0):
        """Add one or more newlines before the next write."""
        self._new_lines = max(self._new_lines, 1 + extra)
        if node is not None and node.lineno != self._last_line:
            self._write_debug_info = node.lineno
            self._last_line = node.lineno

    def signature(self, node, frame, extra_kwargs=None):
        """Writes a function call to the stream for the current node.
        A leading comma is added automatically.  The extra keyword
        arguments may not include python keywords otherwise a syntax
        error could occur.  The extra keyword arguments should be given
        as python dict.
        """
        # if any of the given keyword arguments is a python keyword
        # we have to make sure that no invalid call is created.
        kwarg_workaround = False
        for kwarg in chain((x.key for x in node.kwargs), extra_kwargs or ()):
            if is_python_keyword(kwarg):
                kwarg_workaround = True
                break

        for arg in node.args:
            self.write(", ")
            self.visit(arg, frame)

        if not kwarg_workaround:
            for kwarg in node.kwargs:
                self.write(", ")
                self.visit(kwarg, frame)
            if extra_kwargs is not None:
                for key, value in iteritems(extra_kwargs):
                    self.write(", %s=%s" % (key, value))
        if node.dyn_args:
            self.write(", *")
            self.visit(node.dyn_args, frame)

        if kwarg_workaround:
            if node.dyn_kwargs is not None:
                self.write(", **dict({")
            else:
                self.write(", **{")
            for kwarg in node.kwargs:
                self.write("%r: " % kwarg.key)
                self.visit(kwarg.value, frame)
                self.write(", ")
            if extra_kwargs is not None:
                for key, value in iteritems(extra_kwargs):
                    self.write("%r: %s, " % (key, value))
            if node.dyn_kwargs is not None:
                self.write("}, **")
                self.visit(node.dyn_kwargs, frame)
                self.write(")")
            else:
                self.write("}")

        elif node.dyn_kwargs is not None:
            self.write(", **")
            self.visit(node.dyn_kwargs, frame)

    def pull_dependencies(self, nodes):
        """Pull all the dependencies."""
        visitor = DependencyFinderVisitor()
        for node in nodes:
            visitor.visit(node)
        for dependency in "filters", "tests":
            mapping = getattr(self, dependency)
            for name in getattr(visitor, dependency):
                if name not in mapping:
                    mapping[name] = self.temporary_identifier()
                self.writeline(
                    "%s = environment.%s[%r]" % (mapping[name], dependency, name)
                )

    def enter_frame(self, frame):
        undefs = []
        for target, (action, param) in iteritems(frame.symbols.loads):
            if action == VAR_LOAD_PARAMETER:
                pass
            elif action == VAR_LOAD_RESOLVE:
                self.writeline("%s = %s(%r)" % (target, self.get_resolve_func(), param))
            elif action == VAR_LOAD_ALIAS:
                self.writeline("%s = %s" % (target, param))
            elif action == VAR_LOAD_UNDEFINED:
                undefs.append(target)
            else:
                raise NotImplementedError("unknown load instruction")
        if undefs:
            self.writeline("%s = missing" % " = ".join(undefs))

    def leave_frame(self, frame, with_python_scope=False):
        if not with_python_scope:
            undefs = []
            for target, _ in iteritems(frame.symbols.loads):
                undefs.append(target)
            if undefs:
                self.writeline("%s = missing" % " = ".join(undefs))

    def func(self, name):
        if self.environment.is_async:
            return "async def %s" % name
        return "def %s" % name

    def macro_body(self, node, frame):
        """Dump the function def of a macro or call block."""
        frame = frame.inner()
        frame.symbols.analyze_node(node)
        macro_ref = MacroRef(node)

        explicit_caller = None
        skip_special_params = set()
        args = []
        for idx, arg in enumerate(node.args):
            if arg.name == "caller":
                explicit_caller = idx
            if arg.name in ("kwargs", "varargs"):
                skip_special_params.add(arg.name)
            args.append(frame.symbols.ref(arg.name))

        undeclared = find_undeclared(node.body, ("caller", "kwargs", "varargs"))

        if "caller" in undeclared:
            # In older Jinja versions there was a bug that allowed caller
            # to retain the special behavior even if it was mentioned in
            # the argument list.  However thankfully this was only really
            # working if it was the last argument.  So we are explicitly
            # checking this now and error out if it is anywhere else in
            # the argument list.
            if explicit_caller is not None:
                try:
                    node.defaults[explicit_caller - len(node.args)]
                except IndexError:
                    self.fail(
                        "When defining macros or call blocks the "
                        'special "caller" argument must be omitted '
                        "or be given a default.",
                        node.lineno,
                    )
            else:
                args.append(frame.symbols.declare_parameter("caller"))
            macro_ref.accesses_caller = True
        if "kwargs" in undeclared and "kwargs" not in skip_special_params:
            args.append(frame.symbols.declare_parameter("kwargs"))
            macro_ref.accesses_kwargs = True
        if "varargs" in undeclared and "varargs" not in skip_special_params:
            args.append(frame.symbols.declare_parameter("varargs"))
            macro_ref.accesses_varargs = True

        # macros are delayed, they never require output checks
        frame.require_output_check = False
        frame.symbols.analyze_node(node)
        self.writeline("%s(%s):" % (self.func("macro"), ", ".join(args)), node)
        self.indent()

        self.buffer(frame)
        self.enter_frame(frame)

        self.push_parameter_definitions(frame)
        for idx, arg in enumerate(node.args):
            ref = frame.symbols.ref(arg.name)
            self.writeline("if %s is missing:" % ref)
            self.indent()
            try:
                default = node.defaults[idx - len(node.args)]
            except IndexError:
                self.writeline(
                    "%s = undefined(%r, name=%r)"
                    % (ref, "parameter %r was not provided" % arg.name, arg.name)
                )
            else:
                self.writeline("%s = " % ref)
                self.visit(default, frame)
            self.mark_parameter_stored(ref)
            self.outdent()
        self.pop_parameter_definitions()

        self.blockvisit(node.body, frame)
        self.return_buffer_contents(frame, force_unescaped=True)
        self.leave_frame(frame, with_python_scope=True)
        self.outdent()

        return frame, macro_ref

    def macro_def(self, macro_ref, frame):
        """Dump the macro definition for the def created by macro_body."""
        arg_tuple = ", ".join(repr(x.name) for x in macro_ref.node.args)
        name = getattr(macro_ref.node, "name", None)
        if len(macro_ref.node.args) == 1:
            arg_tuple += ","
        self.write(
            "Macro(environment, macro, %r, (%s), %r, %r, %r, "
            "context.eval_ctx.autoescape)"
            % (
                name,
                arg_tuple,
                macro_ref.accesses_kwargs,
                macro_ref.accesses_varargs,
                macro_ref.accesses_caller,
            )
        )

    def position(self, node):
        """Return a human readable position for the node."""
        rv = "line %d" % node.lineno
        if self.name is not None:
            rv += " in " + repr(self.name)
        return rv

    def dump_local_context(self, frame):
        return "{%s}" % ", ".join(
            "%r: %s" % (name, target)
            for name, target in iteritems(frame.symbols.dump_stores())
        )

    def write_commons(self):
        """Writes a common preamble that is used by root and block functions.
        Primarily this sets up common local helpers and enforces a generator
        through a dead branch.
        """
        self.writeline("resolve = context.resolve_or_missing")
        self.writeline("undefined = environment.undefined")
        # always use the standard Undefined class for the implicit else of
        # conditional expressions
        self.writeline("cond_expr_undefined = Undefined")
        self.writeline("if 0: yield None")

    def push_parameter_definitions(self, frame):
        """Pushes all parameter targets from the given frame into a local
        stack that permits tracking of yet to be assigned parameters.  In
        particular this enables the optimization from `visit_Name` to skip
        undefined expressions for parameters in macros as macros can reference
        otherwise unbound parameters.
        """
        self._param_def_block.append(frame.symbols.dump_param_targets())

    def pop_parameter_definitions(self):
        """Pops the current parameter definitions set."""
        self._param_def_block.pop()

    def mark_parameter_stored(self, target):
        """Marks a parameter in the current parameter definitions as stored.
        This will skip the enforced undefined checks.
        """
        if self._param_def_block:
            self._param_def_block[-1].discard(target)

    def push_context_reference(self, target):
        self._context_reference_stack.append(target)

    def pop_context_reference(self):
        self._context_reference_stack.pop()

    def get_context_ref(self):
        return self._context_reference_stack[-1]

    def get_resolve_func(self):
        target = self._context_reference_stack[-1]
        if target == "context":
            return "resolve"
        return "%s.resolve" % target

    def derive_context(self, frame):
        return "%s.derived(%s)" % (
            self.get_context_ref(),
            self.dump_local_context(frame),
        )

    def parameter_is_undeclared(self, target):
        """Checks if a given target is an undeclared parameter."""
        if not self._param_def_block:
            return False
        return target in self._param_def_block[-1]

    def push_assign_tracking(self):
        """Pushes a new layer for assignment tracking."""
        self._assign_stack.append(set())

    def pop_assign_tracking(self, frame):
        """Pops the topmost level for assignment tracking and updates the
        context variables if necessary.
        """
        vars = self._assign_stack.pop()
        if not frame.toplevel or not vars:
            return
        public_names = [x for x in vars if x[:1] != "_"]
        if len(vars) == 1:
            name = next(iter(vars))
            ref = frame.symbols.ref(name)
            self.writeline("context.vars[%r] = %s" % (name, ref))
        else:
            self.writeline("context.vars.update({")
            for idx, name in enumerate(vars):
                if idx:
                    self.write(", ")
                ref = frame.symbols.ref(name)
                self.write("%r: %s" % (name, ref))
            self.write("})")
        if public_names:
            if len(public_names) == 1:
                self.writeline("context.exported_vars.add(%r)" % public_names[0])
            else:
                self.writeline(
                    "context.exported_vars.update((%s))"
                    % ", ".join(imap(repr, public_names))
                )

    # -- Statement Visitors

    def visit_Template(self, node, frame=None):
        assert frame is None, "no root frame allowed"
        eval_ctx = EvalContext(self.environment, self.name)

        from .runtime import exported

        self.writeline("from __future__ import %s" % ", ".join(code_features))
        self.writeline("from jinja2.runtime import " + ", ".join(exported))

        if self.environment.is_async:
            self.writeline(
                "from jinja2.asyncsupport import auto_await, "
                "auto_aiter, AsyncLoopContext"
            )

        # if we want a deferred initialization we cannot move the
        # environment into a local name
        envenv = not self.defer_init and ", environment=environment" or ""

        # do we have an extends tag at all?  If not, we can save some
        # overhead by just not processing any inheritance code.
        have_extends = node.find(nodes.Extends) is not None

        # find all blocks
        for block in node.find_all(nodes.Block):
            if block.name in self.blocks:
                self.fail("block %r defined twice" % block.name, block.lineno)
            self.blocks[block.name] = block

        # find all imports and import them
        for import_ in node.find_all(nodes.ImportedName):
            if import_.importname not in self.import_aliases:
                imp = import_.importname
                self.import_aliases[imp] = alias = self.temporary_identifier()
                if "." in imp:
                    module, obj = imp.rsplit(".", 1)
                    self.writeline("from %s import %s as %s" % (module, obj, alias))
                else:
                    self.writeline("import %s as %s" % (imp, alias))

        # add the load name
        self.writeline("name = %r" % self.name)

        # generate the root render function.
        self.writeline(
            "%s(context, missing=missing%s):" % (self.func("root"), envenv), extra=1
        )
        self.indent()
        self.write_commons()

        # process the root
        frame = Frame(eval_ctx)
        if "self" in find_undeclared(node.body, ("self",)):
            ref = frame.symbols.declare_parameter("self")
            self.writeline("%s = TemplateReference(context)" % ref)
        frame.symbols.analyze_node(node)
        frame.toplevel = frame.rootlevel = True
        frame.require_output_check = have_extends and not self.has_known_extends
        if have_extends:
            self.writeline("parent_template = None")
        self.enter_frame(frame)
        self.pull_dependencies(node.body)
        self.blockvisit(node.body, frame)
        self.leave_frame(frame, with_python_scope=True)
        self.outdent()

        # make sure that the parent root is called.
        if have_extends:
            if not self.has_known_extends:
                self.indent()
                self.writeline("if parent_template is not None:")
            self.indent()
            if supports_yield_from and not self.environment.is_async:
                self.writeline("yield from parent_template.root_render_func(context)")
            else:
                self.writeline(
                    "%sfor event in parent_template."
                    "root_render_func(context):"
                    % (self.environment.is_async and "async " or "")
                )
                self.indent()
                self.writeline("yield event")
                self.outdent()
            self.outdent(1 + (not self.has_known_extends))

        # at this point we now have the blocks collected and can visit them too.
        for name, block in iteritems(self.blocks):
            self.writeline(
                "%s(context, missing=missing%s):"
                % (self.func("block_" + name), envenv),
                block,
                1,
            )
            self.indent()
            self.write_commons()
            # It's important that we do not make this frame a child of the
            # toplevel template.  This would cause a variety of
            # interesting issues with identifier tracking.
            block_frame = Frame(eval_ctx)
            undeclared = find_undeclared(block.body, ("self", "super"))
            if "self" in undeclared:
                ref = block_frame.symbols.declare_parameter("self")
                self.writeline("%s = TemplateReference(context)" % ref)
            if "super" in undeclared:
                ref = block_frame.symbols.declare_parameter("super")
                self.writeline("%s = context.super(%r, block_%s)" % (ref, name, name))
            block_frame.symbols.analyze_node(block)
            block_frame.block = name
            self.enter_frame(block_frame)
            self.pull_dependencies(block.body)
            self.blockvisit(block.body, block_frame)
            self.leave_frame(block_frame, with_python_scope=True)
            self.outdent()

        self.writeline(
            "blocks = {%s}" % ", ".join("%r: block_%s" % (x, x) for x in self.blocks),
            extra=1,
        )

        # add a function that returns the debug info
        self.writeline(
            "debug_info = %r" % "&".join("%s=%s" % x for x in self.debug_info)
        )

    def visit_Block(self, node, frame):
        """Call a block and register it for the template."""
        level = 0
        if frame.toplevel:
            # if we know that we are a child template, there is no need to
            # check if we are one
            if self.has_known_extends:
                return
            if self.extends_so_far > 0:
                self.writeline("if parent_template is None:")
                self.indent()
                level += 1

        if node.scoped:
            context = self.derive_context(frame)
        else:
            context = self.get_context_ref()

        if (
            supports_yield_from
            and not self.environment.is_async
            and frame.buffer is None
        ):
            self.writeline(
                "yield from context.blocks[%r][0](%s)" % (node.name, context), node
            )
        else:
            loop = self.environment.is_async and "async for" or "for"
            self.writeline(
                "%s event in context.blocks[%r][0](%s):" % (loop, node.name, context),
                node,
            )
            self.indent()
            self.simple_write("event", frame)
            self.outdent()

        self.outdent(level)

    def visit_Extends(self, node, frame):
        """Calls the extender."""
        if not frame.toplevel:
            self.fail("cannot use extend from a non top-level scope", node.lineno)

        # if the number of extends statements in general is zero so
        # far, we don't have to add a check if something extended
        # the template before this one.
        if self.extends_so_far > 0:

            # if we have a known extends we just add a template runtime
            # error into the generated code.  We could catch that at compile
            # time too, but i welcome it not to confuse users by throwing the
            # same error at different times just "because we can".
            if not self.has_known_extends:
                self.writeline("if parent_template is not None:")
                self.indent()
            self.writeline("raise TemplateRuntimeError(%r)" % "extended multiple times")

            # if we have a known extends already we don't need that code here
            # as we know that the template execution will end here.
            if self.has_known_extends:
                raise CompilerExit()
            else:
                self.outdent()

        self.writeline("parent_template = environment.get_template(", node)
        self.visit(node.template, frame)
        self.write(", %r)" % self.name)
        self.writeline(
            "for name, parent_block in parent_template.blocks.%s():" % dict_item_iter
        )
        self.indent()
        self.writeline("context.blocks.setdefault(name, []).append(parent_block)")
        self.outdent()

        # if this extends statement was in the root level we can take
        # advantage of that information and simplify the generated code
        # in the top level from this point onwards
        if frame.rootlevel:
            self.has_known_extends = True

        # and now we have one more
        self.extends_so_far += 1

    def visit_Include(self, node, frame):
        """Handles includes."""
        if node.ignore_missing:
            self.writeline("try:")
            self.indent()

        func_name = "get_or_select_template"
        if isinstance(node.template, nodes.Const):
            if isinstance(node.template.value, string_types):
                func_name = "get_template"
            elif isinstance(node.template.value, (tuple, list)):
                func_name = "select_template"
        elif isinstance(node.template, (nodes.Tuple, nodes.List)):
            func_name = "select_template"

        self.writeline("template = environment.%s(" % func_name, node)
        self.visit(node.template, frame)
        self.write(", %r)" % self.name)
        if node.ignore_missing:
            self.outdent()
            self.writeline("except TemplateNotFound:")
            self.indent()
            self.writeline("pass")
            self.outdent()
            self.writeline("else:")
            self.indent()

        skip_event_yield = False
        if node.with_context:
            loop = self.environment.is_async and "async for" or "for"
            self.writeline(
                "%s event in template.root_render_func("
                "template.new_context(context.get_all(), True, "
                "%s)):" % (loop, self.dump_local_context(frame))
            )
        elif self.environment.is_async:
            self.writeline(
                "for event in (await "
                "template._get_default_module_async())"
                "._body_stream:"
            )
        else:
            if supports_yield_from:
                self.writeline("yield from template._get_default_module()._body_stream")
                skip_event_yield = True
            else:
                self.writeline(
                    "for event in template._get_default_module()._body_stream:"
                )

        if not skip_event_yield:
            self.indent()
            self.simple_write("event", frame)
            self.outdent()

        if node.ignore_missing:
            self.outdent()

    def visit_Import(self, node, frame):
        """Visit regular imports."""
        self.writeline("%s = " % frame.symbols.ref(node.target), node)
        if frame.toplevel:
            self.write("context.vars[%r] = " % node.target)
        if self.environment.is_async:
            self.write("await ")
        self.write("environment.get_template(")
        self.visit(node.template, frame)
        self.write(", %r)." % self.name)
        if node.with_context:
            self.write(
                "make_module%s(context.get_all(), True, %s)"
                % (
                    self.environment.is_async and "_async" or "",
                    self.dump_local_context(frame),
                )
            )
        elif self.environment.is_async:
            self.write("_get_default_module_async()")
        else:
            self.write("_get_default_module()")
        if frame.toplevel and not node.target.startswith("_"):
            self.writeline("context.exported_vars.discard(%r)" % node.target)

    def visit_FromImport(self, node, frame):
        """Visit named imports."""
        self.newline(node)
        self.write(
            "included_template = %senvironment.get_template("
            % (self.environment.is_async and "await " or "")
        )
        self.visit(node.template, frame)
        self.write(", %r)." % self.name)
        if node.with_context:
            self.write(
                "make_module%s(context.get_all(), True, %s)"
                % (
                    self.environment.is_async and "_async" or "",
                    self.dump_local_context(frame),
                )
            )
        elif self.environment.is_async:
            self.write("_get_default_module_async()")
        else:
            self.write("_get_default_module()")

        var_names = []
        discarded_names = []
        for name in node.names:
            if isinstance(name, tuple):
                name, alias = name
            else:
                alias = name
            self.writeline(
                "%s = getattr(included_template, "
                "%r, missing)" % (frame.symbols.ref(alias), name)
            )
            self.writeline("if %s is missing:" % frame.symbols.ref(alias))
            self.indent()
            self.writeline(
                "%s = undefined(%r %% "
                "included_template.__name__, "
                "name=%r)"
                % (
                    frame.symbols.ref(alias),
                    "the template %%r (imported on %s) does "
                    "not export the requested name %s"
                    % (self.position(node), repr(name)),
                    name,
                )
            )
            self.outdent()
            if frame.toplevel:
                var_names.append(alias)
                if not alias.startswith("_"):
                    discarded_names.append(alias)

        if var_names:
            if len(var_names) == 1:
                name = var_names[0]
                self.writeline(
                    "context.vars[%r] = %s" % (name, frame.symbols.ref(name))
                )
            else:
                self.writeline(
                    "context.vars.update({%s})"
                    % ", ".join(
                        "%r: %s" % (name, frame.symbols.ref(name)) for name in var_names
                    )
                )
        if discarded_names:
            if len(discarded_names) == 1:
                self.writeline("context.exported_vars.discard(%r)" % discarded_names[0])
            else:
                self.writeline(
                    "context.exported_vars.difference_"
                    "update((%s))" % ", ".join(imap(repr, discarded_names))
                )

    def visit_For(self, node, frame):
        loop_frame = frame.inner()
        test_frame = frame.inner()
        else_frame = frame.inner()

        # try to figure out if we have an extended loop.  An extended loop
        # is necessary if the loop is in recursive mode if the special loop
        # variable is accessed in the body.
        extended_loop = node.recursive or "loop" in find_undeclared(
            node.iter_child_nodes(only=("body",)), ("loop",)
        )

        loop_ref = None
        if extended_loop:
            loop_ref = loop_frame.symbols.declare_parameter("loop")

        loop_frame.symbols.analyze_node(node, for_branch="body")
        if node.else_:
            else_frame.symbols.analyze_node(node, for_branch="else")

        if node.test:
            loop_filter_func = self.temporary_identifier()
            test_frame.symbols.analyze_node(node, for_branch="test")
            self.writeline("%s(fiter):" % self.func(loop_filter_func), node.test)
            self.indent()
            self.enter_frame(test_frame)
            self.writeline(self.environment.is_async and "async for " or "for ")
            self.visit(node.target, loop_frame)
            self.write(" in ")
            self.write(self.environment.is_async and "auto_aiter(fiter)" or "fiter")
            self.write(":")
            self.indent()
            self.writeline("if ", node.test)
            self.visit(node.test, test_frame)
            self.write(":")
            self.indent()
            self.writeline("yield ")
            self.visit(node.target, loop_frame)
            self.outdent(3)
            self.leave_frame(test_frame, with_python_scope=True)

        # if we don't have an recursive loop we have to find the shadowed
        # variables at that point.  Because loops can be nested but the loop
        # variable is a special one we have to enforce aliasing for it.
        if node.recursive:
            self.writeline(
                "%s(reciter, loop_render_func, depth=0):" % self.func("loop"), node
            )
            self.indent()
            self.buffer(loop_frame)

            # Use the same buffer for the else frame
            else_frame.buffer = loop_frame.buffer

        # make sure the loop variable is a special one and raise a template
        # assertion error if a loop tries to write to loop
        if extended_loop:
            self.writeline("%s = missing" % loop_ref)

        for name in node.find_all(nodes.Name):
            if name.ctx == "store" and name.name == "loop":
                self.fail(
                    "Can't assign to special loop variable in for-loop target",
                    name.lineno,
                )

        if node.else_:
            iteration_indicator = self.temporary_identifier()
            self.writeline("%s = 1" % iteration_indicator)

        self.writeline(self.environment.is_async and "async for " or "for ", node)
        self.visit(node.target, loop_frame)
        if extended_loop:
            if self.environment.is_async:
                self.write(", %s in AsyncLoopContext(" % loop_ref)
            else:
                self.write(", %s in LoopContext(" % loop_ref)
        else:
            self.write(" in ")

        if node.test:
            self.write("%s(" % loop_filter_func)
        if node.recursive:
            self.write("reciter")
        else:
            if self.environment.is_async and not extended_loop:
                self.write("auto_aiter(")
            self.visit(node.iter, frame)
            if self.environment.is_async and not extended_loop:
                self.write(")")
        if node.test:
            self.write(")")

        if node.recursive:
            self.write(", undefined, loop_render_func, depth):")
        else:
            self.write(extended_loop and ", undefined):" or ":")

        self.indent()
        self.enter_frame(loop_frame)

        self.blockvisit(node.body, loop_frame)
        if node.else_:
            self.writeline("%s = 0" % iteration_indicator)
        self.outdent()
        self.leave_frame(
            loop_frame, with_python_scope=node.recursive and not node.else_
        )

        if node.else_:
            self.writeline("if %s:" % iteration_indicator)
            self.indent()
            self.enter_frame(else_frame)
            self.blockvisit(node.else_, else_frame)
            self.leave_frame(else_frame)
            self.outdent()

        # if the node was recursive we have to return the buffer contents
        # and start the iteration code
        if node.recursive:
            self.return_buffer_contents(loop_frame)
            self.outdent()
            self.start_write(frame, node)
            if self.environment.is_async:
                self.write("await ")
            self.write("loop(")
            if self.environment.is_async:
                self.write("auto_aiter(")
            self.visit(node.iter, frame)
            if self.environment.is_async:
                self.write(")")
            self.write(", loop)")
            self.end_write(frame)

    def visit_If(self, node, frame):
        if_frame = frame.soft()
        self.writeline("if ", node)
        self.visit(node.test, if_frame)
        self.write(":")
        self.indent()
        self.blockvisit(node.body, if_frame)
        self.outdent()
        for elif_ in node.elif_:
            self.writeline("elif ", elif_)
            self.visit(elif_.test, if_frame)
            self.write(":")
            self.indent()
            self.blockvisit(elif_.body, if_frame)
            self.outdent()
        if node.else_:
            self.writeline("else:")
            self.indent()
            self.blockvisit(node.else_, if_frame)
            self.outdent()

    def visit_Macro(self, node, frame):
        macro_frame, macro_ref = self.macro_body(node, frame)
        self.newline()
        if frame.toplevel:
            if not node.name.startswith("_"):
                self.write("context.exported_vars.add(%r)" % node.name)
            self.writeline("context.vars[%r] = " % node.name)
        self.write("%s = " % frame.symbols.ref(node.name))
        self.macro_def(macro_ref, macro_frame)

    def visit_CallBlock(self, node, frame):
        call_frame, macro_ref = self.macro_body(node, frame)
        self.writeline("caller = ")
        self.macro_def(macro_ref, call_frame)
        self.start_write(frame, node)
        self.visit_Call(node.call, frame, forward_caller=True)
        self.end_write(frame)

    def visit_FilterBlock(self, node, frame):
        filter_frame = frame.inner()
        filter_frame.symbols.analyze_node(node)
        self.enter_frame(filter_frame)
        self.buffer(filter_frame)
        self.blockvisit(node.body, filter_frame)
        self.start_write(frame, node)
        self.visit_Filter(node.filter, filter_frame)
        self.end_write(frame)
        self.leave_frame(filter_frame)

    def visit_With(self, node, frame):
        with_frame = frame.inner()
        with_frame.symbols.analyze_node(node)
        self.enter_frame(with_frame)
        for target, expr in izip(node.targets, node.values):
            self.newline()
            self.visit(target, with_frame)
            self.write(" = ")
            self.visit(expr, frame)
        self.blockvisit(node.body, with_frame)
        self.leave_frame(with_frame)

    def visit_ExprStmt(self, node, frame):
        self.newline(node)
        self.visit(node.node, frame)

    _FinalizeInfo = namedtuple("_FinalizeInfo", ("const", "src"))
    #: The default finalize function if the environment isn't configured
    #: with one. Or if the environment has one, this is called on that
    #: function's output for constants.
    _default_finalize = text_type
    _finalize = None

    def _make_finalize(self):
        """Build the finalize function to be used on constants and at
        runtime. Cached so it's only created once for all output nodes.

        Returns a ``namedtuple`` with the following attributes:

        ``const``
            A function to finalize constant data at compile time.

        ``src``
            Source code to output around nodes to be evaluated at
            runtime.
        """
        if self._finalize is not None:
            return self._finalize

        finalize = default = self._default_finalize
        src = None

        if self.environment.finalize:
            src = "environment.finalize("
            env_finalize = self.environment.finalize

            def finalize(value):
                return default(env_finalize(value))

            if getattr(env_finalize, "contextfunction", False) is True:
                src += "context, "
                finalize = None  # noqa: F811
            elif getattr(env_finalize, "evalcontextfunction", False) is True:
                src += "context.eval_ctx, "
                finalize = None
            elif getattr(env_finalize, "environmentfunction", False) is True:
                src += "environment, "

                def finalize(value):
                    return default(env_finalize(self.environment, value))

        self._finalize = self._FinalizeInfo(finalize, src)
        return self._finalize

    def _output_const_repr(self, group):
        """Given a group of constant values converted from ``Output``
        child nodes, produce a string to write to the template module
        source.
        """
        return repr(concat(group))

    def _output_child_to_const(self, node, frame, finalize):
        """Try to optimize a child of an ``Output`` node by trying to
        convert it to constant, finalized data at compile time.

        If :exc:`Impossible` is raised, the node is not constant and
        will be evaluated at runtime. Any other exception will also be
        evaluated at runtime for easier debugging.
        """
        const = node.as_const(frame.eval_ctx)

        if frame.eval_ctx.autoescape:
            const = escape(const)

        # Template data doesn't go through finalize.
        if isinstance(node, nodes.TemplateData):
            return text_type(const)

        return finalize.const(const)

    def _output_child_pre(self, node, frame, finalize):
        """Output extra source code before visiting a child of an
        ``Output`` node.
        """
        if frame.eval_ctx.volatile:
            self.write("(escape if context.eval_ctx.autoescape else to_string)(")
        elif frame.eval_ctx.autoescape:
            self.write("escape(")
        else:
            self.write("to_string(")

        if finalize.src is not None:
            self.write(finalize.src)

    def _output_child_post(self, node, frame, finalize):
        """Output extra source code after visiting a child of an
        ``Output`` node.
        """
        self.write(")")

        if finalize.src is not None:
            self.write(")")

    def visit_Output(self, node, frame):
        # If an extends is active, don't render outside a block.
        if frame.require_output_check:
            # A top-level extends is known to exist at compile time.
            if self.has_known_extends:
                return

            self.writeline("if parent_template is None:")
            self.indent()

        finalize = self._make_finalize()
        body = []

        # Evaluate constants at compile time if possible. Each item in
        # body will be either a list of static data or a node to be
        # evaluated at runtime.
        for child in node.nodes:
            try:
                if not (
                    # If the finalize function requires runtime context,
                    # constants can't be evaluated at compile time.
                    finalize.const
                    # Unless it's basic template data that won't be
                    # finalized anyway.
                    or isinstance(child, nodes.TemplateData)
                ):
                    raise nodes.Impossible()

                const = self._output_child_to_const(child, frame, finalize)
            except (nodes.Impossible, Exception):
                # The node was not constant and needs to be evaluated at
                # runtime. Or another error was raised, which is easier
                # to debug at runtime.
                body.append(child)
                continue

            if body and isinstance(body[-1], list):
                body[-1].append(const)
            else:
                body.append([const])

        if frame.buffer is not None:
            if len(body) == 1:
                self.writeline("%s.append(" % frame.buffer)
            else:
                self.writeline("%s.extend((" % frame.buffer)

            self.indent()

        for item in body:
            if isinstance(item, list):
                # A group of constant data to join and output.
                val = self._output_const_repr(item)

                if frame.buffer is None:
                    self.writeline("yield " + val)
                else:
                    self.writeline(val + ",")
            else:
                if frame.buffer is None:
                    self.writeline("yield ", item)
                else:
                    self.newline(item)

                # A node to be evaluated at runtime.
                self._output_child_pre(item, frame, finalize)
                self.visit(item, frame)
                self._output_child_post(item, frame, finalize)

                if frame.buffer is not None:
                    self.write(",")

        if frame.buffer is not None:
            self.outdent()
            self.writeline(")" if len(body) == 1 else "))")

        if frame.require_output_check:
            self.outdent()

    def visit_Assign(self, node, frame):
        self.push_assign_tracking()
        self.newline(node)
        self.visit(node.target, frame)
        self.write(" = ")
        self.visit(node.node, frame)
        self.pop_assign_tracking(frame)

    def visit_AssignBlock(self, node, frame):
        self.push_assign_tracking()
        block_frame = frame.inner()
        # This is a special case.  Since a set block always captures we
        # will disable output checks.  This way one can use set blocks
        # toplevel even in extended templates.
        block_frame.require_output_check = False
        block_frame.symbols.analyze_node(node)
        self.enter_frame(block_frame)
        self.buffer(block_frame)
        self.blockvisit(node.body, block_frame)
        self.newline(node)
        self.visit(node.target, frame)
        self.write(" = (Markup if context.eval_ctx.autoescape else identity)(")
        if node.filter is not None:
            self.visit_Filter(node.filter, block_frame)
        else:
            self.write("concat(%s)" % block_frame.buffer)
        self.write(")")
        self.pop_assign_tracking(frame)
        self.leave_frame(block_frame)

    # -- Expression Visitors

    def visit_Name(self, node, frame):
        if node.ctx == "store" and frame.toplevel:
            if self._assign_stack:
                self._assign_stack[-1].add(node.name)
        ref = frame.symbols.ref(node.name)

        # If we are looking up a variable we might have to deal with the
        # case where it's undefined.  We can skip that case if the load
        # instruction indicates a parameter which are always defined.
        if node.ctx == "load":
            load = frame.symbols.find_load(ref)
            if not (
                load is not None
                and load[0] == VAR_LOAD_PARAMETER
                and not self.parameter_is_undeclared(ref)
            ):
                self.write(
                    "(undefined(name=%r) if %s is missing else %s)"
                    % (node.name, ref, ref)
                )
                return

        self.write(ref)

    def visit_NSRef(self, node, frame):
        # NSRefs can only be used to store values; since they use the normal
        # `foo.bar` notation they will be parsed as a normal attribute access
        # when used anywhere but in a `set` context
        ref = frame.symbols.ref(node.name)
        self.writeline("if not isinstance(%s, Namespace):" % ref)
        self.indent()
        self.writeline(
            "raise TemplateRuntimeError(%r)"
            % "cannot assign attribute on non-namespace object"
        )
        self.outdent()
        self.writeline("%s[%r]" % (ref, node.attr))

    def visit_Const(self, node, frame):
        val = node.as_const(frame.eval_ctx)
        if isinstance(val, float):
            self.write(str(val))
        else:
            self.write(repr(val))

    def visit_TemplateData(self, node, frame):
        try:
            self.write(repr(node.as_const(frame.eval_ctx)))
        except nodes.Impossible:
            self.write(
                "(Markup if context.eval_ctx.autoescape else identity)(%r)" % node.data
            )

    def visit_Tuple(self, node, frame):
        self.write("(")
        idx = -1
        for idx, item in enumerate(node.items):
            if idx:
                self.write(", ")
            self.visit(item, frame)
        self.write(idx == 0 and ",)" or ")")

    def visit_List(self, node, frame):
        self.write("[")
        for idx, item in enumerate(node.items):
            if idx:
                self.write(", ")
            self.visit(item, frame)
        self.write("]")

    def visit_Dict(self, node, frame):
        self.write("{")
        for idx, item in enumerate(node.items):
            if idx:
                self.write(", ")
            self.visit(item.key, frame)
            self.write(": ")
            self.visit(item.value, frame)
        self.write("}")

    def binop(operator, interceptable=True):  # noqa: B902
        @optimizeconst
        def visitor(self, node, frame):
            if (
                self.environment.sandboxed
                and operator in self.environment.intercepted_binops
            ):
                self.write("environment.call_binop(context, %r, " % operator)
                self.visit(node.left, frame)
                self.write(", ")
                self.visit(node.right, frame)
            else:
                self.write("(")
                self.visit(node.left, frame)
                self.write(" %s " % operator)
                self.visit(node.right, frame)
            self.write(")")

        return visitor

    def uaop(operator, interceptable=True):  # noqa: B902
        @optimizeconst
        def visitor(self, node, frame):
            if (
                self.environment.sandboxed
                and operator in self.environment.intercepted_unops
            ):
                self.write("environment.call_unop(context, %r, " % operator)
                self.visit(node.node, frame)
            else:
                self.write("(" + operator)
                self.visit(node.node, frame)
            self.write(")")

        return visitor

    visit_Add = binop("+")
    visit_Sub = binop("-")
    visit_Mul = binop("*")
    visit_Div = binop("/")
    visit_FloorDiv = binop("//")
    visit_Pow = binop("**")
    visit_Mod = binop("%")
    visit_And = binop("and", interceptable=False)
    visit_Or = binop("or", interceptable=False)
    visit_Pos = uaop("+")
    visit_Neg = uaop("-")
    visit_Not = uaop("not ", interceptable=False)
    del binop, uaop

    @optimizeconst
    def visit_Concat(self, node, frame):
        if frame.eval_ctx.volatile:
            func_name = "(context.eval_ctx.volatile and markup_join or unicode_join)"
        elif frame.eval_ctx.autoescape:
            func_name = "markup_join"
        else:
            func_name = "unicode_join"
        self.write("%s((" % func_name)
        for arg in node.nodes:
            self.visit(arg, frame)
            self.write(", ")
        self.write("))")

    @optimizeconst
    def visit_Compare(self, node, frame):
        self.write("(")
        self.visit(node.expr, frame)
        for op in node.ops:
            self.visit(op, frame)
        self.write(")")

    def visit_Operand(self, node, frame):
        self.write(" %s " % operators[node.op])
        self.visit(node.expr, frame)

    @optimizeconst
    def visit_Getattr(self, node, frame):
        if self.environment.is_async:
            self.write("(await auto_await(")

        self.write("environment.getattr(")
        self.visit(node.node, frame)
        self.write(", %r)" % node.attr)

        if self.environment.is_async:
            self.write("))")

    @optimizeconst
    def visit_Getitem(self, node, frame):
        # slices bypass the environment getitem method.
        if isinstance(node.arg, nodes.Slice):
            self.visit(node.node, frame)
            self.write("[")
            self.visit(node.arg, frame)
            self.write("]")
        else:
            if self.environment.is_async:
                self.write("(await auto_await(")

            self.write("environment.getitem(")
            self.visit(node.node, frame)
            self.write(", ")
            self.visit(node.arg, frame)
            self.write(")")

            if self.environment.is_async:
                self.write("))")

    def visit_Slice(self, node, frame):
        if node.start is not None:
            self.visit(node.start, frame)
        self.write(":")
        if node.stop is not None:
            self.visit(node.stop, frame)
        if node.step is not None:
            self.write(":")
            self.visit(node.step, frame)

    @optimizeconst
    def visit_Filter(self, node, frame):
        if self.environment.is_async:
            self.write("await auto_await(")
        self.write(self.filters[node.name] + "(")
        func = self.environment.filters.get(node.name)
        if func is None:
            self.fail("no filter named %r" % node.name, node.lineno)
        if getattr(func, "contextfilter", False) is True:
            self.write("context, ")
        elif getattr(func, "evalcontextfilter", False) is True:
            self.write("context.eval_ctx, ")
        elif getattr(func, "environmentfilter", False) is True:
            self.write("environment, ")

        # if the filter node is None we are inside a filter block
        # and want to write to the current buffer
        if node.node is not None:
            self.visit(node.node, frame)
        elif frame.eval_ctx.volatile:
            self.write(
                "(context.eval_ctx.autoescape and"
                " Markup(concat(%s)) or concat(%s))" % (frame.buffer, frame.buffer)
            )
        elif frame.eval_ctx.autoescape:
            self.write("Markup(concat(%s))" % frame.buffer)
        else:
            self.write("concat(%s)" % frame.buffer)
        self.signature(node, frame)
        self.write(")")
        if self.environment.is_async:
            self.write(")")

    @optimizeconst
    def visit_Test(self, node, frame):
        self.write(self.tests[node.name] + "(")
        if node.name not in self.environment.tests:
            self.fail("no test named %r" % node.name, node.lineno)
        self.visit(node.node, frame)
        self.signature(node, frame)
        self.write(")")

    @optimizeconst
    def visit_CondExpr(self, node, frame):
        def write_expr2():
            if node.expr2 is not None:
                return self.visit(node.expr2, frame)
            self.write(
                "cond_expr_undefined(%r)"
                % (
                    "the inline if-"
                    "expression on %s evaluated to false and "
                    "no else section was defined." % self.position(node)
                )
            )

        self.write("(")
        self.visit(node.expr1, frame)
        self.write(" if ")
        self.visit(node.test, frame)
        self.write(" else ")
        write_expr2()
        self.write(")")

    @optimizeconst
    def visit_Call(self, node, frame, forward_caller=False):
        if self.environment.is_async:
            self.write("await auto_await(")
        if self.environment.sandboxed:
            self.write("environment.call(context, ")
        else:
            self.write("context.call(")
        self.visit(node.node, frame)
        extra_kwargs = forward_caller and {"caller": "caller"} or None
        self.signature(node, frame, extra_kwargs)
        self.write(")")
        if self.environment.is_async:
            self.write(")")

    def visit_Keyword(self, node, frame):
        self.write(node.key + "=")
        self.visit(node.value, frame)

    # -- Unused nodes for extensions

    def visit_MarkSafe(self, node, frame):
        self.write("Markup(")
        self.visit(node.expr, frame)
        self.write(")")

    def visit_MarkSafeIfAutoescape(self, node, frame):
        self.write("(context.eval_ctx.autoescape and Markup or identity)(")
        self.visit(node.expr, frame)
        self.write(")")

    def visit_EnvironmentAttribute(self, node, frame):
        self.write("environment." + node.name)

    def visit_ExtensionAttribute(self, node, frame):
        self.write("environment.extensions[%r].%s" % (node.identifier, node.name))

    def visit_ImportedName(self, node, frame):
        self.write(self.import_aliases[node.importname])

    def visit_InternalName(self, node, frame):
        self.write(node.name)

    def visit_ContextReference(self, node, frame):
        self.write("context")

    def visit_DerivedContextReference(self, node, frame):
        self.write(self.derive_context(frame))

    def visit_Continue(self, node, frame):
        self.writeline("continue", node)

    def visit_Break(self, node, frame):
        self.writeline("break", node)

    def visit_Scope(self, node, frame):
        scope_frame = frame.inner()
        scope_frame.symbols.analyze_node(node)
        self.enter_frame(scope_frame)
        self.blockvisit(node.body, scope_frame)
        self.leave_frame(scope_frame)

    def visit_OverlayScope(self, node, frame):
        ctx = self.temporary_identifier()
        self.writeline("%s = %s" % (ctx, self.derive_context(frame)))
        self.writeline("%s.vars = " % ctx)
        self.visit(node.context, frame)
        self.push_context_reference(ctx)

        scope_frame = frame.inner(isolated=True)
        scope_frame.symbols.analyze_node(node)
        self.enter_frame(scope_frame)
        self.blockvisit(node.body, scope_frame)
        self.leave_frame(scope_frame)
        self.pop_context_reference()

    def visit_EvalContextModifier(self, node, frame):
        for keyword in node.options:
            self.writeline("context.eval_ctx.%s = " % keyword.key)
            self.visit(keyword.value, frame)
            try:
                val = keyword.value.as_const(frame.eval_ctx)
            except nodes.Impossible:
                frame.eval_ctx.volatile = True
            else:
                setattr(frame.eval_ctx, keyword.key, val)

    def visit_ScopedEvalContextModifier(self, node, frame):
        old_ctx_name = self.temporary_identifier()
        saved_ctx = frame.eval_ctx.save()
        self.writeline("%s = context.eval_ctx.save()" % old_ctx_name)
        self.visit_EvalContextModifier(node, frame)
        for child in node.body:
            self.visit(child, frame)
        frame.eval_ctx.revert(saved_ctx)
        self.writeline("context.eval_ctx.revert(%s)" % old_ctx_name)