Fix edge-case in preprocess_data, if label_namer is optional and unset. #16613
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9728144 removed a call to `BoundArguments.apply_defaults` to guard against an API change in Py3.9. As it turns out this means that `all_kwargs[label_namer]` can now fail, in theory, if _preprocess_data is used on a function for which label_namer is an *optional* parameter (because the default won't be set in all_kwargs). Fortunately, 1) there is no such case (it would be semantically questionable to derive the label from a non-required argument...) and 2) the fix is simple (use `all_kwargs.get` instead -- _label_namer properly handles None).
We don't need to evaluate needs_label at the top, we can just do it when needed. Also rename all_kwargs to args_and_kwargs, as it's really a mapping of all arg names to their values, whether they have been passed positionally or by keyword.
dstansby
approved these changes
Mar 1, 2020
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As argued above, I don't think the failing case makes sense semantically anyways... |
timhoffm
approved these changes
Mar 1, 2020
meeseeksmachine
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Mar 1, 2020
…bel_namer is optional and unset.
timhoffm
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Mar 1, 2020
…613-on-v3.2.x Backport PR #16613 on branch v3.2.x (Fix edge-case in preprocess_data, if label_namer is optional and unset.)
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PR Summary
First commit (the important one):
9728144 removed a call to
BoundArguments.apply_defaultsto guardagainst an API change in Py3.9. As it turns out this means that
all_kwargs[label_namer]can now fail, in theory, if _preprocess_datais used on a function for which label_namer is an optional parameter
(because the default won't be set in all_kwargs). Fortunately, 1) there
is no such case (it would be semantically questionable to derive the
label from a non-required argument...) and 2) the fix is simple (use
all_kwargs.getinstead -- _label_namer properly handles None).(TL;DR: 9728144 broke _preprocess_data in an edge case that isn't
exercised anywhere in mpl; it's private API so in theory no one else
should be exercising that edge case but let's still fix it.)
Second commit (just a simplification):
We don't need to evaluate needs_label at the top, we can just do it when
needed. Also rename all_kwargs to args_and_kwargs, as it's really a
mapping of all arg names to their values, whether they have been passed
positionally or by keyword.
PR Checklist