Add seekable() to mmap.mmap - #8405
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mmap already supports seek() and tell(); expose seekable() to match CPython. Confidence: high Scope-risk: narrow Tested: test_mmap, stdlib_mmap snippet, clippy, prek, extra_tests Not-tested: full workspace test blocked by local rustpython-capi SIGSEGV Assisted-by: Codex:gpt-5.6-sol
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📝 WalkthroughWalkthroughAdds Changesmmap seekability
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Pull request overview
This PR adds the mmap.mmap.seekable() method to RustPython’s mmap implementation to match CPython behavior (returning True for both open and closed mappings), and adds a small regression snippet test.
Changes:
- Implement
mmap.mmap.seekable()in the Rustmmapstdlib module. - Add an
extra_tests/snippetsregression that assertsseekable()returnsTrueboth before and afterclose().
Reviewed changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.
| File | Description |
|---|---|
crates/stdlib/src/mmap.rs |
Adds the seekable() pymethod on the mmap type. |
extra_tests/snippets/stdlib_mmap.py |
Adds a snippet regression test covering seekable() on open/closed mappings. |
Comments suppressed due to low confidence (1)
crates/stdlib/src/mmap.rs:1147
- Now that
mmap.mmap.seekable()is implemented, the RustPython-specific@unittest.expectedFailure # TODO: RUSTPYTHON; AttributeError: 'mmap' object has no attribute 'seekable'onLib/test/test_mmap.py::MmapTests.test_basicappears stale and should be removed/updated; otherwise the test may become an unexpected success once the underlying failure is fixed.
#[pymethod]
const fn seekable(&self) -> bool {
true
}
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CI ruff check removes the redundant blank line and treats the auto-fix as a failure. Constraint: CI runs prek with ruff check Confidence: high Scope-risk: narrow Tested: prek run --all-files; cargo run -- extra_tests/snippets/stdlib_mmap.py Assisted-by: Codex:gpt-5.6-sol
The method is invoked at runtime through the Python wrapper, so const qualification provides no benefit. Constraint: Python methods execute at runtime Confidence: high Scope-risk: narrow Tested: prek run --all-files; cargo run -- extra_tests/snippets/stdlib_mmap.py Assisted-by: Codex:gpt-5.6-sol
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* Allow mmap-backed readers to identify seek support mmap already supports seek() and tell(); expose seekable() to match CPython. Confidence: high Scope-risk: narrow Tested: test_mmap, stdlib_mmap snippet, clippy, prek, extra_tests Not-tested: full workspace test blocked by local rustpython-capi SIGSEGV Assisted-by: Codex:gpt-5.6-sol * Keep mmap regression test lint-clean CI ruff check removes the redundant blank line and treats the auto-fix as a failure. Constraint: CI runs prek with ruff check Confidence: high Scope-risk: narrow Tested: prek run --all-files; cargo run -- extra_tests/snippets/stdlib_mmap.py Assisted-by: Codex:gpt-5.6-sol * Keep mmap seekability method conventional The method is invoked at runtime through the Python wrapper, so const qualification provides no benefit. Constraint: Python methods execute at runtime Confidence: high Scope-risk: narrow Tested: prek run --all-files; cargo run -- extra_tests/snippets/stdlib_mmap.py Assisted-by: Codex:gpt-5.6-sol
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Summary
Add
mmap.mmap.seekable(), matching CPython for open and closed mappings.Testing
cargo run --release -- -m test test_mmapcargo run -- extra_tests/snippets/stdlib_mmap.pycargo clippy -p rustpython-stdlib -- -D warningscargo test -p rustpython-stdlibprek run --all-filescd extra_tests && pytest -v(406 passed)Summary by CodeRabbit
New Features
mmap.mmap.seekable()to report whether a memory-mapped object is seekable (always returnstrue).Tests
seekable()on an in-memory mapping before and after closing it.