Align mapping boundaries with Python 3.15 final by youknowdot · Pull Request #9128 · RustPython/RustPython

youknowdot · 2026-10-14T18:39:01Z

Summary

Extract related mapping-boundary compatibility changes from #8954, following CPython v3.15.0 final:

Accept exact dict/frozendict in one-argument str.maketrans, retain integer key objects, and raise the correct exception for unsupported inputs.
Protect exact mutable dictionaries behind mappingproxy from unknown reflected comparison callbacks by passing a copy, while preserving known mapping fast paths and custom mapping behavior.
Encode frozendict through the native JSON encoder, retaining exact-type fast paths and subclass .items() dispatch.

The only supporting change exposes PyOrderedDict within the VM crate for the exact-type comparison. No Lib/ or test files change. JSON array hooks and the pure-Python encoder remain separate work.

Validation

Fresh release build with threading/stdlib/stdio/importlib/host_env: passed.
Thirteen unchanged canonical CPython final methods, each in an isolated 30-second / 1-GiB process: passed, zero skips. Coverage includes maketrans/translate, dict/frozendict/custom mapping/OrderedDict comparisons and reflected mutation protection, plus native JSON nested mappings, skipkeys, ordering and sorting.
Strict VM/stdlib all-target Clippy with compiler/threading/host_env and -D warnings: passed.
Normal hooks and git diff --check: passed.

The initial extraction failed compilation because PyOrderedDict was private on main. Its two crate-local visibility/re-export prerequisites are included; no payload fields or OrderedDict implementation changed.

Canonical methods/helpers were copied unchanged into external bounded runners and verified against final d220409a13b77de7a6c30abe16ea90db01528edc. Full workspace/C-API suites, other platforms, concurrency/stress tests and broad JSON mutation semantics were not run locally; hosted CI remains required. Arbitrary-size integer-key preservation, integer-subclass identity and rejection of mapping subclasses in maketrans were source-reviewed, not covered by these selectors. JSON validation covers the native encoder only.

AI-assisted implementation and validation with OpenAI Codex.

Support frozen mappings in str.maketrans and native JSON encoding, preserve integer translation keys, and protect mappingproxy dictionaries from unknown reflected comparisons. Assisted-by: OpenAI Codex:model version unavailable

coderabbitai · 2026-10-14T18:39:11Z

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Reviewing files that changed from the base of the PR and between 0f93210 and e9f99cc.

📒 Files selected for processing: 5

crates/stdlib/src/json.rs
crates/vm/src/builtins/mappingproxy.rs
crates/vm/src/builtins/str.rs
crates/vm/src/stdlib/_collections/ordered_dict.rs
crates/vm/src/stdlib/mod.rs

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chatgpt-codex-connector · 2026-10-15T01:31:50Z

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Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-10-15T01:40:44.364445Z	`e9f99cc`	Draft marked ready

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Reviewed commit: e9f99cc388

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chatgpt-codex-connector · 2026-10-15T01:40:42Z

+            && obj.class().is(vm.ctx.types.dict_type)
+            && !(other.class().is(vm.ctx.types.dict_type)
+                || other.class().is(vm.ctx.types.frozendict_type)
+                || other.class().is(vm.ctx.types.mappingproxy_type)


Validate the mapping inside a whitelisted proxy

When other is an exact mappingproxy around an untrusted mapping, this exemption still exposes the protected dictionary: for MappingProxyType(victim) == MappingProxyType(Evil()), the outer slot skips the copy here, dict comparison returns NotImplemented, and the reflected proxy unwraps Evil, whose __eq__ then receives the original victim and can call clear() on it. Only exempt another proxy after verifying that its wrapped mapping is itself a known safe fast path (or remove this exemption), otherwise the reflected-callback protection is bypassable.

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Align mapping boundaries with Python 3.15 final

e9f99cc

Support frozen mappings in str.maketrans and native JSON encoding, preserve integer translation keys, and protect mappingproxy dictionaries from unknown reflected comparisons. Assisted-by: OpenAI Codex:model version unavailable

youknowone approved these changes Oct 15, 2026

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youknowone marked this pull request as ready for review October 15, 2026 01:31

youknowone merged commit 3ab5c0c into RustPython:main Oct 15, 2026
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chatgpt-codex-connector Bot reviewed Oct 15, 2026

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Align mapping boundaries with Python 3.15 final - #9128

Align mapping boundaries with Python 3.15 final#9128
youknowone merged 1 commit into
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youknowdot:split/mapping-boundaries-315

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