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"""Backport of tokenize.open from Python 3.5
This is the exact Python 3.5 with the following differences:
- detect_encoding_ex is detect_encoding from Python 3.5 returning also a bool whether a cookie was found
- detect_encoding calls detect_encoding_ex, so that its signature is the same as in Python 3.5
- function read_source_lines was added
"""
from codecs import lookup, BOM_UTF8
from io import TextIOWrapper, open as _builtin_open
import re
re_ASCII = 256 # not present in Python 2
cookie_re = re.compile(r'^[ \t\f]*#.*?coding[:=][ \t]*([-\w.]+)', re_ASCII)
blank_re = re.compile(br'^[ \t\f]*(?:[#\r\n]|$)', re_ASCII)
def _get_normal_name(orig_enc):
"""Imitates get_normal_name in tokenizer.c."""
# Only care about the first 12 characters.
enc = orig_enc[:12].lower().replace("_", "-")
if enc == "utf-8" or enc.startswith("utf-8-"):
return "utf-8"
if enc in ("latin-1", "iso-8859-1", "iso-latin-1") or \
enc.startswith(("latin-1-", "iso-8859-1-", "iso-latin-1-")):
return "iso-8859-1"
return orig_enc
def detect_encoding(readline):
"""
The detect_encoding() function is used to detect the encoding that should
be used to decode a Python source file. It requires one argument, readline,
in the same way as the tokenize() generator.
It will call readline a maximum of twice, and return the encoding used
(as a string) and a list of any lines (left as bytes) it has read in.
It detects the encoding from the presence of a utf-8 bom or an encoding
cookie as specified in pep-0263. If both a bom and a cookie are present,
but disagree, a SyntaxError will be raised. If the encoding cookie is an
invalid charset, raise a SyntaxError. Note that if a utf-8 bom is found,
'utf-8-sig' is returned.
If no encoding is specified, then the default of 'utf-8' will be returned.
"""
return detect_encoding_ex(readline)[:2]
def detect_encoding_ex(readline):
try:
filename = readline.__self__.name
except AttributeError:
filename = None
bom_found = False
encoding = None
default = 'utf-8'
def read_or_stop():
try:
return readline()
except StopIteration:
return b''
def find_cookie(line):
try:
# Decode as UTF-8. Either the line is an encoding declaration,
# in which case it should be pure ASCII, or it must be UTF-8
# per default encoding.
line_string = line.decode('utf-8')
except UnicodeDecodeError:
msg = "invalid or missing encoding declaration"
if filename is not None:
msg = '{} for {!r}'.format(msg, filename)
raise SyntaxError(msg)
match = cookie_re.match(line_string)
if not match:
return None
encoding = _get_normal_name(match.group(1))
try:
codec = lookup(encoding)
except LookupError:
# This behaviour mimics the Python interpreter
if filename is None:
msg = "unknown encoding: " + encoding
else:
msg = "unknown encoding for {!r}: {}".format(filename,
encoding)
raise SyntaxError(msg)
if bom_found:
if encoding != 'utf-8':
# This behaviour mimics the Python interpreter
if filename is None:
msg = 'encoding problem: utf-8'
else:
msg = 'encoding problem for {!r}: utf-8'.format(filename)
raise SyntaxError(msg)
encoding += '-sig'
return encoding
first = read_or_stop()
if first.startswith(BOM_UTF8):
bom_found = True
first = first[3:]
default = 'utf-8-sig'
if not first:
return default, [], False
encoding = find_cookie(first)
if encoding:
return encoding, [first], True
if not blank_re.match(first):
return default, [first], False
second = read_or_stop()
if not second:
return default, [first], False
encoding = find_cookie(second)
if encoding:
return encoding, [first, second], True
return default, [first, second], False
def open(filename):
"""Open a file in read only mode using the encoding detected by
detect_encoding().
"""
buffer = _builtin_open(filename, 'rb')
try:
encoding, lines = detect_encoding(buffer.readline)
buffer.seek(0)
text = TextIOWrapper(buffer, encoding, line_buffering=True)
text.mode = 'r'
return text
except:
buffer.close()
raise
def read_source_lines(filename):
buffer = _builtin_open(filename, 'rb')
try:
encoding, lines, cookie_present = detect_encoding_ex(buffer.readline)
buffer.seek(0)
text = TextIOWrapper(buffer, encoding, line_buffering=True)
text.mode = 'r'
except:
buffer.close()
raise
with text:
if cookie_present:
for i in lines:
yield text.readline().replace("coding", "Coding")
# so compile() won't complain about encoding declatation in a Unicode string
# see 2.7/Python/ast.c:228
for line in text:
yield line
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