-
-
Notifications
You must be signed in to change notification settings - Fork 2.6k
/
expression.py
329 lines (262 loc) · 9.64 KB
/
expression.py
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
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
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 ( '(' name '=' value ( ', ' name '=' value )* ')')*
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.
"""
from __future__ import annotations
import ast
import dataclasses
import enum
import keyword
import re
import types
from typing import Iterator
from typing import Literal
from typing import Mapping
from typing import NoReturn
from typing import overload
from typing import Protocol
from typing import Sequence
__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"
EQUAL = "="
STRING = "str"
COMMA = ","
@dataclasses.dataclass(frozen=True)
class Token:
__slots__ = ("type", "value", "pos")
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
elif input[pos] == "=":
yield Token(TokenType.EQUAL, "=", pos)
pos += 1
elif input[pos] == ",":
yield Token(TokenType.COMMA, ",", pos)
pos += 1
elif (quote_char := input[pos]) in ("'", '"'):
end_quote_pos = input.find(quote_char, pos + 1)
if end_quote_pos == -1:
raise ParseError(
pos + 1,
f'closing quote "{quote_char}" is missing',
)
value = input[pos : end_quote_pos + 1]
if (backslash_pos := input.find("\\")) != -1:
raise ParseError(
backslash_pos + 1,
r'escaping with "\" not supported in marker expression',
)
yield Token(TokenType.STRING, value, pos)
pos += len(value)
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)
@overload
def accept(self, type: TokenType, *, reject: Literal[True]) -> Token: ...
@overload
def accept(
self, type: TokenType, *, reject: Literal[False] = False
) -> Token | None: ...
def accept(self, type: TokenType, *, reject: bool = False) -> Token | None:
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.Constant(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:
name = ast.Name(IDENT_PREFIX + ident.value, ast.Load())
if s.accept(TokenType.LPAREN):
ret = ast.Call(func=name, args=[], keywords=all_kwargs(s))
s.accept(TokenType.RPAREN, reject=True)
else:
ret = name
return ret
s.reject((TokenType.NOT, TokenType.LPAREN, TokenType.IDENT))
BUILTIN_MATCHERS = {"True": True, "False": False, "None": None}
def single_kwarg(s: Scanner) -> ast.keyword:
keyword_name = s.accept(TokenType.IDENT, reject=True)
if not keyword_name.value.isidentifier():
raise ParseError(
keyword_name.pos + 1,
f"not a valid python identifier {keyword_name.value}",
)
if keyword.iskeyword(keyword_name.value):
raise ParseError(
keyword_name.pos + 1,
f"unexpected reserved python keyword `{keyword_name.value}`",
)
s.accept(TokenType.EQUAL, reject=True)
if value_token := s.accept(TokenType.STRING):
value: str | int | bool | None = value_token.value[1:-1] # strip quotes
else:
value_token = s.accept(TokenType.IDENT, reject=True)
if (
(number := value_token.value).isdigit()
or number.startswith("-")
and number[1:].isdigit()
):
value = int(number)
elif value_token.value in BUILTIN_MATCHERS:
value = BUILTIN_MATCHERS[value_token.value]
else:
raise ParseError(
value_token.pos + 1,
f'unexpected character/s "{value_token.value}"',
)
ret = ast.keyword(keyword_name.value, ast.Constant(value))
return ret
def all_kwargs(s: Scanner) -> list[ast.keyword]:
ret = [single_kwarg(s)]
while s.accept(TokenType.COMMA):
ret.append(single_kwarg(s))
return ret
class MatcherCall(Protocol):
def __call__(self, name: str, /, **kwargs: str | int | bool | None) -> bool: ...
@dataclasses.dataclass
class MatcherNameAdapter:
matcher: MatcherCall
name: str
def __bool__(self) -> bool:
return self.matcher(self.name)
def __call__(self, **kwargs: str | int | bool | None) -> bool:
return self.matcher(self.name, **kwargs)
class MatcherAdapter(Mapping[str, MatcherNameAdapter]):
"""Adapts a matcher function to a locals mapping as required by eval()."""
def __init__(self, matcher: MatcherCall) -> None:
self.matcher = matcher
def __getitem__(self, key: str) -> MatcherNameAdapter:
return MatcherNameAdapter(matcher=self.matcher, name=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: MatcherCall) -> 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 = bool(eval(self.code, {"__builtins__": {}}, MatcherAdapter(matcher)))
return ret