fix: text_fast_path leakage between nested maps + release candid 0.10.29#732
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Pull request overview
Fixes a deserialization bug where the text_fast_path optimization for BTreeMap<String, V> could incorrectly affect nested map key decoding when the inner map’s key type is not Text, leading to a “Type mismatch” during enum key deserialization.
Changes:
- Track the string-key fast-path decision per map by adding
key_text_fasttoStyle::Map. - Update
MapAccess::next_key_seedto use the per-mapkey_text_fast(instead of the global flag) and to settext_fast_pathbased on the current map’s key type before key deserialization. - Add a regression test covering nested maps with a non-text (enum) key type.
Reviewed changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.
| File | Description |
|---|---|
| rust/candid/src/de.rs | Scopes text-key fast-path behavior per map to prevent leakage into nested map key decoding. |
| rust/candid/tests/serde.rs | Adds a regression test for nested map decoding where the inner map has a non-text enum key. |
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Bump `candid` and `candid_derive` 0.10.28 → 0.10.29 to ship the nested-map `text_fast_path` leakage fix, and add a 2026-05-27 CHANGELOG entry. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
lwshang
changed the title
lwshang
approved these changes
May 27, 2026
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Fix
text_fast_pathleaking from an outer text-keyed map into an inner map with non-text keys, which caused a spurious "Type mismatch" during decoding. Releases candid 0.10.29.