1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
|
r"""Evaluate match expressions, as used by `-k` and `-m`.
The grammar is:
expression: expr? EOF
expr: and_expr ('or' and_expr)*
and_expr: not_expr ('and' not_expr)*
not_expr: 'not' not_expr | '(' expr ')' | ident
ident: (\w|:|\+|-|\.|\[|\]|\\|/)+
The semantics are:
- Empty expression evaluates to False.
- ident evaluates to True of False according to a provided matcher function.
- or/and/not evaluate according to the usual boolean semantics.
"""
import ast
import enum
import re
import types
from typing import Callable
from typing import Iterator
from typing import Mapping
from typing import Optional
from typing import Sequence
from typing import TYPE_CHECKING
import attr
if TYPE_CHECKING:
from typing import NoReturn
__all__ = [
"Expression",
"ParseError",
]
class TokenType(enum.Enum):
LPAREN = "left parenthesis"
RPAREN = "right parenthesis"
OR = "or"
AND = "and"
NOT = "not"
IDENT = "identifier"
EOF = "end of input"
@attr.s(frozen=True, slots=True, auto_attribs=True)
class Token:
type: TokenType
value: str
pos: int
class ParseError(Exception):
"""The expression contains invalid syntax.
:param column: The column in the line where the error occurred (1-based).
:param message: A description of the error.
"""
def __init__(self, column: int, message: str) -> None:
self.column = column
self.message = message
def __str__(self) -> str:
return f"at column {self.column}: {self.message}"
class Scanner:
__slots__ = ("tokens", "current")
def __init__(self, input: str) -> None:
self.tokens = self.lex(input)
self.current = next(self.tokens)
def lex(self, input: str) -> Iterator[Token]:
pos = 0
while pos < len(input):
if input[pos] in (" ", "\t"):
pos += 1
elif input[pos] == "(":
yield Token(TokenType.LPAREN, "(", pos)
pos += 1
elif input[pos] == ")":
yield Token(TokenType.RPAREN, ")", pos)
pos += 1
else:
match = re.match(r"(:?\w|:|\+|-|\.|\[|\]|\\|/)+", input[pos:])
if match:
value = match.group(0)
if value == "or":
yield Token(TokenType.OR, value, pos)
elif value == "and":
yield Token(TokenType.AND, value, pos)
elif value == "not":
yield Token(TokenType.NOT, value, pos)
else:
yield Token(TokenType.IDENT, value, pos)
pos += len(value)
else:
raise ParseError(
pos + 1,
f'unexpected character "{input[pos]}"',
)
yield Token(TokenType.EOF, "", pos)
def accept(self, type: TokenType, *, reject: bool = False) -> Optional[Token]:
if self.current.type is type:
token = self.current
if token.type is not TokenType.EOF:
self.current = next(self.tokens)
return token
if reject:
self.reject((type,))
return None
def reject(self, expected: Sequence[TokenType]) -> "NoReturn":
raise ParseError(
self.current.pos + 1,
"expected {}; got {}".format(
" OR ".join(type.value for type in expected),
self.current.type.value,
),
)
# True, False and None are legal match expression identifiers,
# but illegal as Python identifiers. To fix this, this prefix
# is added to identifiers in the conversion to Python AST.
IDENT_PREFIX = "$"
def expression(s: Scanner) -> ast.Expression:
if s.accept(TokenType.EOF):
ret: ast.expr = ast.NameConstant(False)
else:
ret = expr(s)
s.accept(TokenType.EOF, reject=True)
return ast.fix_missing_locations(ast.Expression(ret))
def expr(s: Scanner) -> ast.expr:
ret = and_expr(s)
while s.accept(TokenType.OR):
rhs = and_expr(s)
ret = ast.BoolOp(ast.Or(), [ret, rhs])
return ret
def and_expr(s: Scanner) -> ast.expr:
ret = not_expr(s)
while s.accept(TokenType.AND):
rhs = not_expr(s)
ret = ast.BoolOp(ast.And(), [ret, rhs])
return ret
def not_expr(s: Scanner) -> ast.expr:
if s.accept(TokenType.NOT):
return ast.UnaryOp(ast.Not(), not_expr(s))
if s.accept(TokenType.LPAREN):
ret = expr(s)
s.accept(TokenType.RPAREN, reject=True)
return ret
ident = s.accept(TokenType.IDENT)
if ident:
return ast.Name(IDENT_PREFIX + ident.value, ast.Load())
s.reject((TokenType.NOT, TokenType.LPAREN, TokenType.IDENT))
class MatcherAdapter(Mapping[str, bool]):
"""Adapts a matcher function to a locals mapping as required by eval()."""
def __init__(self, matcher: Callable[[str], bool]) -> None:
self.matcher = matcher
def __getitem__(self, key: str) -> bool:
return self.matcher(key[len(IDENT_PREFIX) :])
def __iter__(self) -> Iterator[str]:
raise NotImplementedError()
def __len__(self) -> int:
raise NotImplementedError()
class Expression:
"""A compiled match expression as used by -k and -m.
The expression can be evaluated against different matchers.
"""
__slots__ = ("code",)
def __init__(self, code: types.CodeType) -> None:
self.code = code
@classmethod
def compile(self, input: str) -> "Expression":
"""Compile a match expression.
:param input: The input expression - one line.
"""
astexpr = expression(Scanner(input))
code: types.CodeType = compile(
astexpr,
filename="<pytest match expression>",
mode="eval",
)
return Expression(code)
def evaluate(self, matcher: Callable[[str], bool]) -> bool:
"""Evaluate the match expression.
:param matcher:
Given an identifier, should return whether it matches or not.
Should be prepared to handle arbitrary strings as input.
:returns: Whether the expression matches or not.
"""
ret: bool = eval(self.code, {"__builtins__": {}}, MatcherAdapter(matcher))
return ret
|
