[thekevinbot]

Slice B of #1111: the Python SDK stops carrying its own port of extension resolution and reaches the core contract landed in #1124.

What moved

Python kept three decisions the core already knows how to make:

• is this entry a package or a file → dirsql._dirsql.is_bare_name
• which configs parse, does any name a package, what does each literal path resolve to against its own config's directory → dirsql._dirsql.plan_config_extensions
• which installed file is the loadable → dirsql._dirsql.select_loadable

It keeps only the two halves the core cannot have: reading the config files off disk, and locating an installed package with importlib.util.find_spec.

The PyO3 layer stays pure — Python reads each config and passes (abs_path, contents | None) pairs; the core parses and plans. Adding an fs-reading plan_config_files to the core was the obvious alternative and was rejected: a Rust unit test may call only super:: and pure std, so an fs-reading function cannot be unit-tested, and diff-scoped cargo-mutants would leave a surviving mutant in the untested reader.

Seven internal modules go away (is_bare_name, has_bare_name, load_extension_entries, resolve_entries, platform_patterns, resolve_config_extensions, toml_module) against two added (read_config, plan_entry_path, split apart to satisfy one-function-per-file). resolve_config_extension_specs — the singular resolver — had no production caller and goes with them. The tomli dependency on Python 3.10 goes too: the core parses the TOML now.

Why there is no pushed-RED commit

This is a behavior-preserving refactor plus removals, both exempt from the pushed-RED CI gate. The existing suites cover every path and stayed green throughout: same resolved paths, same intervene-or-not decision, and the core's SelectError renders the Python wording verbatim, so the error messages are byte-identical.

One normalization, which I judged inconsequential — please push back if you disagree. The core treats a backslash as a path separator on every host, where is_bare_name used os.altsep (None on POSIX). is_bare_name checks the loadable-suffix list first, so the only value that reclassifies is one with a backslash and no loadable suffix — e.g. a\b. On the old path that was a bare name, went to importlib.util.find_spec, and raised could not resolve extension package 'a\\b'; on the new path it is a literal path and fails at load. Both error. No migration fragment on that basis.

Platform scoping is preserved: select_loadable is handed a PLATFORM_SUFFIXES list (.dylib on macOS, .dll/.pyd on Windows, .so elsewhere) that mirrors the deleted _platform_patterns, so a package shipping loadables for several platforms still resolves rather than going ambiguous. is_bare_name keeps the full four-suffix list, matching the deleted _LOADABLE_SUFFIXES.

Manual verification

Built the repo's tests/fixtures/testext cdylib (registers dirsql_testext_answer() -> 42), staged it as mypkg/testext0.so in a temp dir on PYTHONPATH, and wrote a .dirsql.toml whose [[dirsql.extension]].path is the bare name mypkg.

$ dirsql query -c .dirsql.toml 'SELECT dirsql_testext_answer() AS answer, (SELECT count(*) FROM files) AS files'
[{"answer":42,"files":1}]

Same through the SDK, both entry points:

DirSQL(config=...)                            -> [{'answer': 42, 'files': 1}]
DirSQL(root, extensions=[{'path': 'mypkg'}])  -> [{'programmatic': 42}]

The bare name resolved through plan_config_extensions → select_loadable to the absolute .so, which SQLite then loaded.

E2E Verification

• Ran e2e suites locally for every affected SDK
• Python SDK e2e: pass (37 passed)
• TypeScript SDK e2e: N/A — no packages/ts change
• Rust core e2e (if applicable): N/A — no packages/rust change
• packages/python/e2e-attestations/<branch>.json receipt written if packages/python changed (just e2e-attest-python)
• packages/ts/e2e-attestations/<branch>.json receipt written if packages/ts changed (just e2e-attest-ts) — N/A
• Command(s) run: just e2e-attest-python; cargo test --manifest-path packages/python/Cargo.toml --features extension-module; uv run pytest dirsql tests
• Result summary: 37 e2e passed, 91 colocated + 131 integration passed, 15 binding-crate Rust tests passed.

Changelog / Migrations

• Changelog fragment added under <root>/<pkg>/changelog.d/ for each changed package (or: skip-changelog trailer on a commit with reason)
• Migration fragment added under <root>/<pkg>/migrations.d/ (or: not required — additive/bugfix only) — not required: behavior-preserving refactor, every deleted module is private to the package and none is exported from dirsql/__init__.py.

Parity

Restoring parity, with intentional drift that slice C closes. PARITY.md gains a paragraph on where the planning lives. Python now reaches the shared core contract; TypeScript still carries its own port and is tracked by #1121, the next slice.

Gates run

one-function-per-file, unit-lint, colocated-test, integration-lint, unit coverage (100%), unit mutation (7 mutants, 0 survivors), declared-deps, plus the rust-python-binding lane's colocated-test and unit-lint. ruff check, ruff format --check, ty check --error all, cargo fmt, and cargo clippy --workspace --features cli -- -D warnings all clean.

Fixes #1120