bpo-35282: Add a return value to lib2to3.refactor_file and refactor_dir

[martindemello]

lib2to3.refactor.refactor_file returns None (file read failed), True (file was written to) or False (file was not written to)
lib2to3.refactor.refactor_dir returns a list of changed files

https://bugs.python.org/issue35282

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[zware]

This looks like a reasonable change to me, though the refactor_file docstring could do with an update.

[benjaminp]

Is this really enough? You don't want to distinguish changed files from unreadable ones?

[martindemello]

@benjaminp do you mean refactor_dir should distinguish between files that could not be read and files that were simply not refactored?

[benjaminp]

Maybe. I suppose I want to understand the usecase for this. Starting to provide a list return value prevents us from extending the returned information in the future.

[martindemello]

sorry, missed ths comment. my use case was to run modernize on a list of files and see which ones had and had not been changed - if modernize had touched a file at all i wanted to do extra processing on it (e.g. run a formatter), but leave untouched files alone.

[iritkatriel]

Closed under bpo-45544.