8000 Support typing.TYPE_CHECKING. · python/mypy@345a457 · GitHub
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Commit 345a457

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Guido van Rossum
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Support typing.TYPE_CHECKING.
Fixes #2165. This is not completely correct (it'll trigger on *any* variable named TYPE_CHECKING) but I think that's acceptable. We should be able to phase out MYPY once this is in the next release.
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4 files changed

+46
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‎mypy/build.py

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@@ -1472,6 +1472,7 @@ def dispatch(sources: List[BuildSource], manager: BuildManager) -> None:
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manager.log("Loaded graph with %d nodes" % len(graph))
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process_graph(graph, manager)
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if manager.options.warn_unused_ignores:
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# TODO: This could also be a per-file option.
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manager.errors.generate_unused_ignore_notes()
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‎mypy/semanal.py

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@@ -3023,7 +3023,7 @@ def infer_if_condition_value(expr: Node, pyversion: Tuple[int, int], platform: s
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result = ALWAYS_TRUE if pyversion[0] == 2 else ALWAYS_FALSE
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elif name == 'PY3':
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result = ALWAYS_TRUE if pyversion[0] == 3 else ALWAYS_FALSE
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elif name == 'MYPY':
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elif name == 'MYPY' or name == 'TYPE_CHECKING':
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result = ALWAYS_TRUE
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if negated:
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if result == ALWAYS_TRUE:

‎test-data/unit/check-unreachable-code.test

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@@ -90,6 +90,48 @@ else:
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None + ''
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[builtins fixtures/bool.pyi]
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[case testTypeCheckingConditional]
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import typing
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if typing.TYPE_CHECKING:
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import pow123 # E
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else:
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import xyz753
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[out]
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main:3: error: Cannot find module named 'pow123'
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main:3: note: (Perhaps setting MYPYPATH or using the "--silent-imports" flag would help)
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[case testTypeCheckingConditionalFromImport]
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from typing import TYPE_CHECKING
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if TYPE_CHECKING:
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import pow123 # E
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else:
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import xyz753
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[out]
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main:3: error: Cannot find module named 'pow123'
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main:3: note: (Perhaps setting MYPYPATH or using the "--silent-imports" flag would help)
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[case testNegatedTypeCheckingConditional]
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import typing
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if not typing.TYPE_CHECKING:
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import pow123 # E
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else:
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import xyz753
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[builtins fixtures/bool.pyi]
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[out]
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main:5: error: Cannot find module named 'xyz753'
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main:5: note: (Perhaps setting MYPYPATH or using the "--silent-imports" flag would help)
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[case testUndefinedTypeCheckingConditional]
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if not TYPE_CHECKING: # E
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import pow123
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else:
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import xyz753
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[builtins fixtures/bool.pyi]
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[out]
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main:1: error: Name 'TYPE_CHECKING' is not defined
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main:4: error: Cannot find module named 'xyz753'
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main:4: note: (Perhaps setting MYPYPATH or using the "--silent-imports" flag would help)
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[case testConditionalClassDefPY3]
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def f(): pass
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PY3 = f()

‎test-data/unit/lib-stub/typing.pyi

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@@ -84,3 +84,5 @@ def NewType(name: str, tp: Type[T]) -> Callable[[T], T]:
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def new_type(x):
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return x
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return new_type
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TYPE_CHECKING = 1

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