gh-110941: Fix json.dump encoding dict subclasses as empty (continued) - #150631
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eendebakpt wants to merge 7 commits into
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gh-110941: Fix json.dump encoding dict subclasses as empty (continued)#150631eendebakpt wants to merge 7 commits into
eendebakpt wants to merge 7 commits into
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See python#110941 for full details but the tldr is that the C optimised JSON encoder did not handle `dict` subclasses correctly and encoded them as empty if they did not put something into `super()`'s storage.
Co-authored-by: Pieter Eendebak <pieter.eendebak@gmail.com>
Co-authored-by: Pieter Eendebak <pieter.eendebak@gmail.com>
Co-authored-by: Pieter Eendebak <pieter.eendebak@gmail.com>
…110941 # Conflicts: # Modules/_json.c
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This PR is stale because it has been open for 90 days with no activity. |
eendebakpt
commented
Aug 31, 2026
| // Only take the fast path for exact dicts: a subclass may keep its | ||
| // contents outside the dict storage, so PyDict_GET_SIZE could be 0 while | ||
| // the mapping is non-empty (gh-110941). | ||
| if (PyAnyDict_CheckExact(dct) && PyDict_GET_SIZE(dct) == 0) { |
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A variation would be to use PyMapping_Size. That is slightly slower for an exact dict, but will cover dict subclasses.
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This is a continuation of #111036 which has stalled. The PR is the same, exact that we only handle the fast path for exact dicts. This keeps the code a bit cleaner.
json.dumpsaccesses dict internals even for dict subclasses #110941