Support six.with_metaclass #3364
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mypy/semanal.py
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| @@ -953,6 +955,28 @@ def analyze_base_classes(self, defn: ClassDef) -> None: | |||
| if defn.info.is_enum and defn.type_vars: | |||
| self.fail("Enum class cannot be generic", defn) | |||
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| def get_base_type_exprs(self, defn: ClassDef) -> List[Expression]: | |||
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Document that this may modify defn.metaclass -- maybe also include this information in the method name.
mypy/semanal.py
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| and all(kind == ARG_POS for kind in base_expr.arg_kinds)): | ||
| metaclass = base_expr.args[0] | ||
| if isinstance(metaclass, NameExpr): | ||
| defn.metaclass = metaclass.name |
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Should this be a fully qualified name? Anyway, test code like this:
from m import M
import six
class C(six.with_metaclass(M)): ...
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I just copied this from analyze_metaclass(). Added a test, it seems to work.
test-data/unit/check-classes.test
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| class C2(C1, six.with_metaclass(M)): pass # E: Invalid base class | ||
| class C3(six.with_metaclass(A)): pass # E: Metaclasses not inheriting from 'type' are not supported | ||
| class C4(six.with_metaclass(M), metaclass=M): pass # E: Invalid base class | ||
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Add test cases:
- Dynamic metaclass with
six.with_metaclass, such assix.with_metaclass(f()). - Member expression as metaclass, such as
six.with_metaclass(m.M). - Metaclass from-imported from another module (
from m import M); also mentioned above.
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@JukkaL: Do you have time for another review? |
mypy/semanal.py
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| @@ -902,7 +902,9 @@ def analyze_base_classes(self, defn: ClassDef) -> None: | |||
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| base_types = [] # type: List[Instance] | |||
| info = defn.info | |||
| for base_expr in defn.base_type_exprs: | |||
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| base_type_exprs = self.check_with_metaclass(defn) | |||
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I think this is not a right place for this check. It should be rather processed before (or in) clean_up_bases_and_infer_type_variables, this is why you see problems with Generic in #3366.
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Thanks! Much better now. I also change the API for check_with_metaclass() a bit, but it does exactly the same thing (except returns both values). Please review again.
This allows Mypy to understand six.with_metaclass: python/mypy#3364
Fixes #1764
This doesn't add support for
@six.add_metaclass(M)-- if that's required we'll add it later (we should open a separate issue for that).