8000 Implement most common sys.version_info and sys.platform checks by gvanrossum · Pull Request #1942 · python/mypy · GitHub
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Implement most common sys.version_info and sys.platform checks #1942

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Merged
merged 9 commits into from
Jul 27, 2016
Merged

Implement most common sys.version_info and sys.platform checks #1942

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3cbf1b4
Add sys.version_info checks. With some basic tests.
Jul 26, 2016
cea303b
Add tests for negated sys.version checks, and fix the code.
Jul 26, 2016
8816915
More tests for sys.version_info[<slice>]. Found no new bugs (except i…
Jul 26, 2016
4e84874
Add more slicing tests. Fixed a bug one of these found.
Jul 26, 2016
d28d75b
Add sys.platform support (no test yet).
Jul 26, 2016
c70a97d
Add tests for sys.platform. Fix type error. Change rules for sys.vers…
Jul 26, 2016
5eaae5a
Be more careful with win32 platform in crawl.py.
Jul 26, 2016
70bcaea
Add TODOs in response to code review.
Jul 27, 2016
65cf9ac
Add more tests for sys.version_info/platform.
Jul 27, 2016
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160 changes: 152 additions & 8 deletions mypy/semanal.py
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Original file line number Diff line number Diff line change
Expand Up @@ -43,6 +43,7 @@
traverse the entire AST.
"""

import sys
from typing import (
List, Dict, Set, Tuple, cast, Any, overload, TypeVar, Union, Optional, Callable
)
Expand All @@ -64,7 +65,7 @@
SetComprehension, DictionaryComprehension, TYPE_ALIAS, TypeAliasExpr,
YieldExpr, ExecStmt, Argument, BackquoteExpr, ImportBase, AwaitExpr,
IntExpr, FloatExpr, UnicodeExpr,
COVARIANT, CONTRAVARIANT, INVARIANT, UNBOUND_IMPORTED,
COVARIANT, CONTRAVARIANT, INVARIANT, UNBOUND_IMPORTED, LITERAL_YES,
)
from mypy.visitor import NodeVisitor
from mypy.traverser import TraverserVisitor
Expand Down Expand Up @@ -2781,17 +2782,22 @@ def infer_if_condition_value(expr: Node, pyversion: Tuple[int, int]) -> int:
if alias.op == 'not':
expr = alias.expr
negated = True
result = TRUTH_VALUE_UNKNOWN
if isinstance(expr, NameExpr):
name = expr.name
elif isinstance(expr, MemberExpr):
name = expr.name
result = TRUTH_VALUE_UNKNOWN
if name == 'PY2':
result = ALWAYS_TRUE if pyversion[0] == 2 else ALWAYS_FALSE
elif name == 'PY3':
result = ALWAYS_TRUE if pyversion[0] == 3 else ALWAYS_FALSE
elif name == 'MYPY':
result = ALWAYS_TRUE
else:
result = consider_sys_version_info(expr, pyversion)
if result == TRUTH_VALUE_UNKNOWN:
result = consider_sys_platform(expr, sys.platform)
if result == TRUTH_VALUE_UNKNOWN:
if name == 'PY2':
result = ALWAYS_TRUE if pyversion[0] == 2 else ALWAYS_FALSE
elif name == 'PY3':
result = ALWAYS_TRUE if pyversion[0] == 3 else ALWAYS_FALSE
elif name == 'MYPY':
result = ALWAYS_TRUE
if negated:
if result == ALWAYS_TRUE:
result = ALWAYS_FALSE
Expand All @@ -2800,6 +2806,144 @@ def infer_if_condition_value(expr: Node, pyversion: Tuple[int, int]) -> int:
return result


def consider_sys_version_info(expr: Node, pyversion: Tuple[int, ...]) -> int:
"""Consider whether expr is a comparison involving sys.version_info.

Return ALWAYS_TRUE, ALWAYS_FALSE, or TRUTH_VALUE_UNKNOWN.
"""
# Cases supported:
# - sys.version_info[<int>] <compare_op> <int>
# - sys.version_info[:<int>] <compare_op> <tuple_of_n_ints>
# - sys.version_info <compare_op> <tuple_of_1_or_2_ints>
# (in this case <compare_op> must be >, >=, <, <=, but cannot be ==, !=)
if not isinstance(expr, ComparisonExpr):
return TRUTH_VALUE_UNKNOWN
# Let's not yet support chained comparisons.
if len(expr.operators) > 1:
return TRUTH_VALUE_UNKNOWN
op = expr.operators[0]
if op not in ('==', '!=', '<=', '>=', '<', '>'):
return TRUTH_VALUE_UNKNOWN
thing = contains_int_or_tuple_of_ints(expr.operands[1])
if thing is None:
return TRUTH_VALUE_UNKNOWN
index = contains_sys_version_info(expr.operands[0])
if isinstance(index, int) and isinstance(thing, int):
# sys.version_info[i] <compare_op> k
if 0 <= index <= 1:
return fixed_comparison(pyversion[index], op, thing)
else:
return TRUTH_VALUE_UNKNOWN
elif isinstance(index, tuple) and isinstance(thing, tuple):
# Why doesn't mypy see that index can't be None here?
lo, hi = cast(tuple, index)
if lo is None:
lo = 0
if hi is None:
hi = 2
if 0 <= lo < hi <= 2:
val = pyversion[lo:hi]
if len(val) == len(thing) or len(val) > len(thing) and op not in ('==', '!='):
return fixed_comparison(val, op, thing)
return TRUTH_VALUE_UNKNOWN


def consider_sys_platform(expr: Node, platform: str) -> int:
"""Consider whether expr is a comparison involving sys.platform.

Return ALWAYS_TRUE, ALWAYS_FALSE, or TRUTH_VALUE_UNKNOWN.
"""
# Cases supported:
# - sys.platform == 'posix'
# - sys.platform != 'win32'
# TODO: Maybe support e.g.:
# - sys.platform.startswith('win')
if not isinstance(expr, ComparisonExpr):
return TRUTH_VALUE_UNKNOWN
# Let's not yet support chained comparisons.
if len(expr.operators) > 1:
return TRUTH_VALUE_UNKNOWN
op = expr.operators[0]
if op not in ('==', '!='):
return TRUTH_VALUE_UNKNOWN
if not is_sys_attr(expr.operands[0], 'platform'):
return TRUTH_VALUE_UNKNOWN
right = expr.operands[1]
if not isinstance(right, (StrExpr, UnicodeExpr)):
return TRUTH_VALUE_UNKNOWN
return fixed_comparison(platform, op, right.value)


Targ = TypeVar('Targ', int, str, Tuple[int, ...])


def fixed_comparison(left: Targ, op: str, right: Targ) -> int:
rmap = {False: ALWAYS_FALSE, True: ALWAYS_TRUE}
if op == '==':
return rmap[left == right]
if op == '!=':
return rmap[left != right]
if op == '<=':
return rmap[left <= right]
if op == '>=':
return rmap[left >= right]
if op == '<':
return rmap[left < right]
if op == '>':
return rmap[left > right]
return TRUTH_VALUE_UNKNOWN


def contains_int_or_tuple_of_ints(expr: Node) -> Union[None, int, Tuple[int], Tuple[int, ...]]:
if isinstance(expr, IntExpr):
return expr.value
if isinstance(expr, TupleExpr):
if expr.literal == LITERAL_YES:
thing = []
for x in expr.items:
if not isinstance(x, IntExpr):
return None
thing.append(x.value)
return tuple(thing)
return None


def contains_sys_version_info(expr: Node) -> Union[None, int, Tuple[Optional[int], Optional[int]]]:
if is_sys_attr(expr, 'version_info'):
return (None, None) # Same as sys.version_info[:]
if isinstance(expr, IndexExpr) and is_sys_attr(expr.base, 'version_info'):
index = expr.index
if isinstance(index, IntExpr):
return index.value
if isinstance(index, SliceExpr):
if index.stride is not None:
if not isinstance(index.stride, IntExpr) or index.stride.value != 1:
return None
begin = end = None
if index.begin_index is not None:
if not isinstance(index.begin_index, IntExpr):
return None
begin = index.begin_index.value
if index.end_index is not None:
if not isinstance(index.end_index, IntExpr):
return None
end = index.end_index.value
return (begin, end)
return None


def is_sys_attr(expr: Node, name: str) -> bool:
# TODO: This currently doesn't work with code like this:
# - import sys as _sys
# - from sys import version_info
if isinstance(expr, MemberExpr) and expr.name == name:
if isinstance(expr.expr, NameExpr) and expr.expr.name == 'sys':
# TODO: Guard against a local named sys, etc.
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Also this won't work with things like import sys as _sys -- I found 8 files that did this in the Python 2.7 stdlib.

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Another thing that doesn't work is from sys import platform (which is arguably questionable style and doesn't seem very common). Not sure if we should support it -- one option is to describe it as unsupported in our docs.

# (Though later passes will still do most checking.)
return True
return False


def mark_block_unreachable(block: Block) -> None:
block.is_unreachable = True
block.accept(MarkImportsUnreachableVisitor())
Expand Down
16 changes: 10 additions & 6 deletions test-data/samples/crawl.py
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Original file line number Diff line number Diff line change
Expand Up @@ -20,9 +20,10 @@


ARGS = argparse.ArgumentParser(description="Web crawler")
ARGS.add_argument(
'--iocp', action='store_true', dest='iocp',
default=False, help='Use IOCP event loop (Windows only)')
if sys.platform == 'win32':
ARGS.add_argument(
'--iocp', action='store_true', dest='iocp',
default=False, help='Use IOCP event loop (Windows only)')
ARGS.add_argument(
'--select', action='store_true', dest='select',
default=False, help='Use Select event loop instead of default')
Expand Down Expand Up @@ -824,9 +825,12 @@ def main() -> None:
log = Logger(args.level)

if args.iocp:
from asyncio import ProactorEventLoop
loop = ProactorEventLoop() # type: ignore
asyncio.set_event_loop(loop)
if sys.platform == 'win32':
from asyncio import ProactorEventLoop
loop = ProactorEventLoop() # type: ignore
asyncio.set_event_loop(loop)
else:
assert False
elif args.select:
loop = asyncio.SelectorEventLoop() # type: ignore
asyncio.set_event_loop(loop)
Expand Down
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