gh-154002: Fix exception chaining in pickle _Unpickler._instantiate#154003
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fedonman wants to merge 2 commits into
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gh-154002: Fix exception chaining in pickle _Unpickler._instantiate#154003fedonman wants to merge 2 commits into
_Unpickler._instantiate#154003fedonman wants to merge 2 commits into
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…iate When a class constructor raised TypeError during old-style (INST/OBJ) unpickling, the pure-Python unpickler did `raise TypeError(msg, err.__traceback__)`, which stored the traceback object in the exception's args and performed no real chaining (__cause__ stayed None). Use `raise TypeError(msg) from err` instead. The C implementation is unaffected; it lets the original error propagate.
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When unpickling an old-style instance (the INST and OBJ opcodes) and the class constructor raises
TypeError, the pure-Pythonpickle._Unpickler._instantiatedid:Passing
err.__traceback__as a second positional argument put the traceback object into the exception'sargs, so it leaked intostr()and there was no real chaining (__cause__stayedNone). This changes it to chain properly and drop the traceback argument:It is a leftover from the Python 2 way of carrying a traceback. It was
sys.exc_info()[2]until gh-102799 mechanically turned it intoerr.__traceback__without noticing the value was being passed as a constructor argument. The C_pickleunpickler does not wrap the error at all, so it is unaffected.I added a regression test that loads an INST pickle whose constructor raises
TypeErrorand checks that no traceback object ends up inargsand that the original error is chained. It runs against both unpickler implementations and fails without the fix.Fixes #154002.
_Unpickler._instantiatemangles a constructor TypeError (traceback in args, no chaining) #154002