* Let xml.sax initialize pyexpat-backed parsers
RustPython already exposes an Expat-like XML parser, but xml.sax expects a few setup APIs before parsing. Add compatible parser setup methods and constants without pretending to implement full Expat external entity behavior.
Constraint: Lib/test changes only remove expectedFailure markers for tests that now pass; test bodies and assertions are unchanged.
Rejected: Implementing full Expat parameter entity parsing | xml-rs does not expose that configuration and the immediate failure is the missing setup API.
Confidence: high
Scope-risk: narrow
Directive: Keep SetParamEntityParsing as a compatibility shim unless the backend grows real Expat-style entity parsing support.
Tested: PATH=/tmp/pyshim:$PATH prek run --all-files
Tested: cargo run --quiet -- extra_tests/snippets/stdlib_xml.py
Tested: cargo run --release -- -m test test_sax
Tested: cargo run --release -- -m test test_pyexpat
Tested: cargo test --workspace --exclude rustpython-capi --exclude rustpython_wasm --exclude rustpython-compiler-source --exclude rustpython-venvlauncher --features threading --no-default-features --features stdlib,importlib,stdio,encodings,sqlite,ssl-rustls-aws-lc,host_env && (cd crates/capi && cargo test)
Tested: PYO3_CONFIG_FILE=$PWD/crates/capi/pyo3-rustpython.config cargo test --workspace --exclude rustpython_wasm --exclude rustpython-venvlauncher
Tested: cargo build --release --features sqlite && cd extra_tests && /tmp/rustpython-extra-tests-venv/bin/python -m pytest -v
Tested: cargo clippy --workspace --exclude rustpython-capi --exclude rustpython_wasm --exclude rustpython-compiler-source --exclude rustpython-venvlauncher --features threading --no-default-features --features stdlib,importlib,stdio,encodings,sqlite,ssl-rustls-aws-lc,host_env
Assisted-by: Codex:gpt-5.5
* Keep XML follow-up tests aligned with passing behavior
The pyexpat setup API compatibility fix also makes pulldom's basic parse smoke test pass, so keep RustPython expected-failure markers aligned with current behavior and apply the ruff import-spacing fix.
Constraint: Test body and assertions remain unchanged.
Confidence: high
Scope-risk: narrow
Tested: cargo run --release -- -m test test_pulldom -v
Tested: cargo run --release -- -m test test_sax
Tested: cargo run --release -- -m test test_pyexpat
Tested: cargo run --quiet -- extra_tests/snippets/stdlib_xml.py
Tested: PATH=/tmp/pyshim:/Users/kbm/.codex/tmp/arg0/codex-arg0ejsdGi:/Users/kbm/.omx-runs/run-20260703105454-4fab/.omx/runtime/bin:/Users/kbm/.nvm/versions/node/v24.15.0/bin:/Users/kbm/Library/Java/JavaVirtualMachines/temurin-21.0.9/Contents/Home/bin:/Users/kbm/.antigravity/antigravity/bin:/opt/homebrew/opt/mysql-client/bin:/opt/homebrew/bin:/opt/homebrew/sbin:/usr/local/bin:/System/Cryptexes/App/usr/bin:/usr/bin:/bin:/usr/sbin:/sbin:/var/run/com.apple.security.cryptexd/codex.system/bootstrap/usr/local/bin:/var/run/com.apple.security.cryptexd/codex.system/bootstrap/usr/bin:/var/run/com.apple.security.cryptexd/codex.system/bootstrap/usr/appleinternal/bin:/Library/Apple/usr/bin:/var/folders/vq/1mhmtsbs2kj_03tsx74kd1mm0000gn/T//cmux-cli-shims/93BA47BD-630C-4ED3-8573-0FE6ABFAE824:/Applications/cmux.app/Contents/Resources/bin:/Users/kbm/.nvm/versions/node/v24.15.0/bin:/Users/kbm/Library/Java/JavaVirtualMachines/temurin-21.0.9/Contents/Home/bin:/Users/kbm/.antigravity/antigravity/bin:/opt/homebrew/opt/mysql-client/bin:/var/folders/vq/1mhmtsbs2kj_03tsx74kd1mm0000gn/T/cmux-cli-shims/93BA47BD-630C-4ED3-8573-0FE6ABFAE824:/Applications/Visual Studio Code.app/Contents/Resources/app/bin:/Applications/Visual Studio Code.app/Contents/Resources/app/bin:/Applications/Visual Studio Code.app/Contents/Resources/app/bin prek run --all-files
Tested: cargo build --release --features sqlite && cd extra_tests && /tmp/rustpython-extra-tests-venv/bin/python -m pytest -v
Tested: PYO3_CONFIG_FILE=/Users/kbm/IdeaProjects/RustPython/crates/capi/pyo3-rustpython.config cargo test --workspace --exclude rustpython_wasm --exclude rustpython-venvlauncher
Tested: cargo clippy --workspace --exclude rustpython-capi --exclude rustpython_wasm --exclude rustpython-compiler-source --exclude rustpython-venvlauncher --features threading --no-default-features --features stdlib,importlib,stdio,encodings,sqlite,ssl-rustls-aws-lc,host_env
Assisted-by: Codex:gpt-5.5
Kwak Byoung Min