[FanWu-ai]

Summary

postlex.always_accept affects which terminals survive grammar compilation, but postlex is excluded from the parser cache key. Reusing a cache built without postlex (or with a different retained-terminal set) can discard required tokens and reject otherwise valid input.

• Include the retained-terminal set in the cache key.
• Snapshot its iterable once and reuse it for grammar compilation, preserving one-shot iterators.
• Leave lexer-only mode's iterable untouched.
• Cover both basic/contextual lexers, changing postlex requirements, repeated cache loads, one-shot iterators, and a lexer-only control.

Validation

• Regression on original code fails in both lexer modes with UnexpectedCharacters.
• Pristine Python 3.10.22: 1337 tests, OK (148 existing skips).
• Fixed Python 3.10.22: 1340 tests, OK (148 existing skips), including all 8 Nearley tests with unchanged Js2Py==0.68.
• Python 3.12 and 3.13: 1332 tests each, OK (148 existing skips); pinned Js2Py cannot run Nearley on these interpreters.
• mypy==1.12: all 34 source files pass.
• All configured pre-commit checks and git diff --check pass.

AI assistance was used to investigate, implement, review, and test this change.