Commits on Dec 25, 2023

1. Fix mypy warning "Missing return statement" …

   In git.index.base.IndexFile.from_tree, control was never able to
   fall off the end, but mypy reported a "Missing return statement"
   because it could not infer that the context manager didn't suppress
   any exceptions.
   
   This was for two reasons. An ExitStack context manager suppresses
   exceptions in some uses and not others, depending on the context
   manager objects its enter_context method is called with. In this
   case, that was sufficient to produce the mypy warning regardless of
   other changes, so I converted it to nested with-statements. The
   nesting depth is only 2, so this is not really any worse. (I also
   reworded the comments for clarity and adjusted their spacing.)
   
   The more important cause, however, could also produce this warning
   in code that uses GitPython, as git.index.util.TemporaryFileSwap is
   public. Its __exit__ method was annotated to return bool. This was
   itself reported by mypy as an error, because a context manager
   __exit__ method that never suppresses exceptions should either
   always (implicitly) return None and be annotated as such, or it can
   return False as this implementation does but should then have its
   return type annotated as Literal[False].
   
   So this also changes TemporaryFileSwap.__exit__'s return type
   annotation from bool to Literal[False]. If this were nonpublic or
   being newly designed, it may be better for it to instead return
   None implicitly, but I think that would technically be a breaking
   change (though it would be very unusual, and not a good idea, for
   any code to ever rely on the distinction).
   
   With both these changes made, both those mypy warnings go away, and
   code using GitPython will not get a warning if it makes similar
   direct use of TemporaryFileSwap.
   
   (An alternative might be to dedent the return statement out of the
   with-statement in IndexFile.from_tree, but this would make less
   clear to readers that it does not suppress exceptions. Furthermore,
   the change to TemporaryFileSwap.__exit__ would still have to be
   made for mypy to consider it correctly typed.)

   

   EliahKagan committed Dec 25, 2023
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