* Keep StringIO text operations CPython-compatible
Constraint: email.feedparser depends on StringIO(newline='') recognizing CR, LF, and CRLF boundaries.
Rejected: an email-specific parser workaround | StringIO is the shared root cause.
Confidence: high
Scope-risk: moderate
Directive: Keep internal storage byte-based; convert only at StringIO API boundaries.
Tested: prek run --all-files; test_memoryio; test_email; full workspace verification by contributor
Assisted-by: Codex:gpt-5.6-sol
* Run restored StringIO conformance tests
Constraint: upstream StringIO tests already cover the repaired behavior.
Rejected: new RustPython-only regression tests | existing CPython coverage is sufficient.
Confidence: high
Scope-risk: narrow
Directive: Remove expected-failure markers only while the inherited tests pass.
Tested: prek run --all-files; test_memoryio; test_email
Assisted-by: Codex:gpt-5.6-sol
* Keep StringIO newline handling consistent
Constraint: StringIO must apply its newline mode consistently when constructing, writing, and reading text.\nRejected: a readline-only fix | it leaves CR and CRLF modes internally inconsistent.\nConfidence: high\nScope-risk: moderate\nDirective: Keep StringIO buffer contents valid WTF-8 before using unchecked views.\nTested: prek run --all-files; cargo clippy -p rustpython-vm -- -D warnings; test_memoryio; test_shlex; test_email; workspace excluding rustpython-capi; full workspace manually verified by contributor\nNot-tested: local rustpython-capi workspace test crashes with a pre-existing macOS SIGSEGV\nAssisted-by: Codex:gpt-5.6-sol
Kwak Byoung Min