When I refactor code I often find myself tediously adding type annotations that are obvious from context: functions that don't return anything, boolean flags, etcetera. That's where autotyping comes in: it automatically adds those types and inserts the right annotations.

It is built as a LibCST codemod; see the LibCST documentation for more information on how to use codemods.

Here's how to use it:

• pip install autotyping
• Make sure you have a .libcst.codemod.yaml with 'autotyper' in the modules list. For an example, see the .libcst.codemod.yaml in this repo.
• Run python -m libcst.tool codemod autotyping.AutotypeCommand /path/to/my/code

By default it does nothing; you have to add flags to make it do more transformations. The following are supported:

• Annotating return types:
  • --none-return: add a -> None return type to functions without any return, yield, or raise in their body
  • --scalar-return: add a return annotation to functions that only return literal bool, str, bytes, int, or float objects.
• Annotationg parameter types:
  • --bool-param: add a : bool annotation to any function parameter with a default of True or False
  • --int-param, --float-param, --str-param, --bytes-param: add an annotation to any parameter for which the default is a literal int, float, str, or bytes object
  • --annotate-optional foo:bar.Baz: for any parameter of the form foo=None, add Baz, imported from bar, as the type. For example, use --annotate-optional uid:my_types.Uid to annotate any uid in your codebase with a None default as Optional[my_types.Uid].
  • --annotate-named-param foo:bar.Baz: annotate any parameter with no default that is named foo with bar.Baz. For example, use --annotate-named-param uid:my_types.Uid to annotate any uid parameter in your codebase with no default as my_types.Uid.
• Annotating magical methods:
  • --annotate-magics: add type annotation to certain magic methods. Currently this does the following:
    • __str__ returns str
    • __repr__ returns str
    • __len__ returns int
    • __init__ returns None
    • __del__ returns None
    • __bool__ returns bool
    • __bytes__ returns bytes
    • __format__ returns str
    • __contains__ returns bool
    • __complex__ returns complex
    • __int__ returns int
    • __float__ returns float
    • __index__ returns int
    • __exit__: the three parameters are Optional[Type[BaseException]], Optional[BaseException], and Optional[TracebackType]
    • __aexit__: same as __exit__
  • --annotate-imprecise-magics: add imprecise type annotations for some additional magic methods. Currently this adds typing.Iterator return annotations to __iter__, __await__, and __reversed__. These annotations should have a generic parameter to indicate what you're iterating over, but that's too hard for autotyping to figure out.

Things to add:

• Infer -> bool as the return type if all return statements are boolean expressions like ==.

Changelog

21.12.0 (December 21, 2021)

• Initial PyPI release