a6d67f7477
Using `sys.excepthook` to silence the must-use warning has some false negatives: applications may catch the exception and then quit normally, e.g. becaue the error is well known and does not require a traceback to be shown (which would be noisy). The current implementation prints even more noise in that case. In addition to the existing heuristic, silence the warning if *nothing* has been elaborated, which is almost always a reliable sign. It doesn't work if multiple designs are independently created in the application and some of them are dropped without being used, but this is unavoidable as it is not distinguishable from the mistake this warning is attempting to prevent. Fixes #848.
48 lines
1.4 KiB
Python
48 lines
1.4 KiB
Python
import sys
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import warnings
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from ._utils import get_linter_option
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__all__ = ["UnusedMustUse", "MustUse"]
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class UnusedMustUse(Warning):
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pass
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class MustUse:
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_MustUse__silence = False
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_MustUse__warning = UnusedMustUse
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def __new__(cls, *args, src_loc_at=0, **kwargs):
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frame = sys._getframe(1 + src_loc_at)
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self = super().__new__(cls)
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self._MustUse__used = False
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self._MustUse__context = dict(
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filename=frame.f_code.co_filename,
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lineno=frame.f_lineno,
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source=self)
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return self
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def __del__(self):
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if self._MustUse__silence:
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return
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if getattr(self._MustUse__warning, "_MustUse__silence", False):
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return
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if hasattr(self, "_MustUse__used") and not self._MustUse__used:
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if get_linter_option(self._MustUse__context["filename"],
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self._MustUse__warning.__name__, bool, True):
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warnings.warn_explicit(
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"{!r} created but never used".format(self), self._MustUse__warning,
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**self._MustUse__context)
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_old_excepthook = sys.excepthook
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def _silence_elaboratable(type, value, traceback):
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# Don't show anything if the interpreter crashed; that'd just obscure the exception
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# traceback instead of helping.
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MustUse._MustUse__silence = True
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_old_excepthook(type, value, traceback)
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sys.excepthook = _silence_elaboratable
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