python
DefaultDict of a TypedDict confuses mypy
Hi 👋 ! I have the following test code:
from collections import defaultdict
from typing import DefaultDict
from mypy_extensions import TypedDict
RepoPath = str
RepoStatus = TypedDict('RepoStatus', {
'branch': str,
'remote': str,
'clean': bool,
# ...
}, total=False)
State2 = defaultdict(RepoStatus) # type: DefaultDict[RepoPath, RepoStatus]
State3 = defaultdict(dict) # type: DefaultDict[RepoPath, RepoStatus]
State4 = defaultdict(lambda: RepoStatus()) # type: DefaultDict[RepoPath, RepoStatus]
State5 = defaultdict(lambda: dict()) # type: DefaultDict[RepoPath, RepoStatus]
State6 = defaultdict(lambda: {}) # type: DefaultDict[RepoPath, RepoStatus]
mypy only accepts the definition of 4 and 6. A pic is easy to follow here
mypy output:
16:10 error mypy Argument 1 to "defaultdict" has incompatible type "Type[RepoStatus]"; expected
"Optional[Callable[[], RepoStatus]]"
17:10 error mypy Argument 1 to "defaultdict" has incompatible type "Type[Dict[Any, Any]]";
expected "Optional[Callable[[], RepoStatus]]"
19:10 error mypy Argument 1 to "defaultdict" has incompatible type "Callable[[], Dict[<nothing>,
<nothing>]]"; expected "Optional[Callable[[], RepoStatus]]"
19:22 error mypy Incompatible return value type (got "Dict[<nothing>, <nothing>]", expected
"RepoStatus")
Ideally the def of State3, just defaultdict(dict), should work, shouldn't it? It is also very surprising that there is a difference between 5 and 6.
mypy 0.720
Yeah, it would be nice if all the cases would be supported by mypy. I think that at least case 5 could be easy to support. 2 and 3 might be harder or require more ad hoc changes.
And thanks for the detailed report!
I just checked that with my PR https://github.com/python/mypy/pull/19254 everything except State3 works (that one will require some hardcore special-casing probably).
