New submission from Andreas H. <ahanga...@gmx.net>:
TypedDict does not resolve cross-module ForwardRefs when the ForwardRef is not
a direct one.
In other words the fix GH-27017 (issue 41249) for TypedDict seems incomplete.
The same issue seem to exist for NamedTuple.
Example:
#module.py
TD = typing.TypedDict("TD", {'test': typing.List[typing.Optional['Y']]})
class Y:
pass
# other module
class TDSub(module.TD):
a: int
get_type_hints(TDSub)
# -> Exception NameError: Y not found
On the other hand, with direct ForwardRef, as e.g. in
TD = typing.TypedDict("TD", {'test': 'Y' } )
it works (that was indeed fixed by GH-27017)
Same issue exists for NamedTuple. There neither of the above works, i.e.
cross-module ForwardRefs are never resolve (but they could - als NamedTuple has
the __module__ member set with to calling module). I am not sure if inheritance
for NamedTuple is supported so I do not know if it is really a bug.
The problem in the code is that in TypedDict the `module` parameter is passed
only onto the immediate ForwardRef. One option could be to recursively walk the
type and search for unpatched ForwardRefs and set the module parameter.
On the other hand, the retroactive patching of forward refs is problematic as
it may mess with the caching mechanism im typing.py. There may be a type with
ForwardRef already in cache (and used by more than one user), but only for one
user the `module` is to be updated. So probably a correct implementation is
tricky, or some other way has to be found to update the `module` of ForwardRefs
(e.g. by copying the type tree).
For NamedTuple the whole mechanism of passing the `module` parameter to the
ForwardRefs is not done (not even for direct ForwardRef ones).
Not sure how important this (likely not very) is as I do not use TypedDict and
NamedTuple. This is just to report it.
----------
components: Library (Lib)
messages: 410547
nosy: AlexWaygood, Jelle Zijlstra, andreash, gvanrossum, kj, kumaraditya303,
sobolevn
priority: normal
severity: normal
status: open
title: TypedDict and NamedTuple do not evaluate cross-module ForwardRef in all
cases
type: behavior
versions: Python 3.10, Python 3.11
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Python tracker <rep...@bugs.python.org>
<https://bugs.python.org/issue46373>
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