Re-fix exception caching in dviread. #28906
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timhoffm
reviewed
Sep 30, 2024
lib/matplotlib/cbook.py
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| @@ -32,6 +32,15 @@ | |||
| from matplotlib import _api, _c_internal_utils | |||
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| class _ExceptionProxy: | |||
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Naming: This is not exactly a proxy. "A proxy is an interface to something else" (wikipedia). This class is not an interface.
Maybe _ExceptionInfo or _ExceptionPlaceholder would be a better name.
Also a docstring would be helpful. Maybe:
Suggested change
| class _ExceptionProxy: | |
| class _ExceptionInfo: | |
| """ | |
| A class to carry exception information around. | |
| This is used to store and later raise exceptions. It's an alternative to directly storing | |
| Exception instances and circumvents traceback-related issues. Caching tracebacks | |
| can keep user's objects in local namespaces alive indefinitely. This can lead to very | |
| surprising memory issues for users and will result in incorrect tracebacks. |
You might even add a classmethod from_exception(exc) for convenience.
lib/matplotlib/cbook.py
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| self._cls = cls | ||
| self._args = args | ||
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| def exception(self): |
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| def exception(self): | |
| def to_exception(self): |
which then reads raise exc_info.to_exception().
The original solution using with_traceback didn't actually work because with_traceback doesn't return a new exception instance but rather modifies the original one in place, and the traceback will then be attached to it by the raise statement. Instead, we actually need to build a new instance, so reuse the _ExceptionProxy machinery from font_manager (slightly expanded).
ksunden
approved these changes
Oct 2, 2024
QuLogic
approved these changes
Oct 2, 2024
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The original solution using with_traceback didn't actually work because with_traceback doesn't return a new exception instance but rather modifies the original one in place, and the traceback will then be attached to it by the raise statement.
Instead, we actually need to build a new instance, so reuse the _ExceptionProxy machinery from font_manager (slightly expanded).
Redo of #28899; sorry about that...
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