headroom/crates
chopratejas f5f465418b feat(rust): retire python diff_compressor, ship rust-only via pyo3
The python `DiffCompressor` is replaced by a thin pyo3-backed shim that
delegates to `headroom._core.DiffCompressor`. There is no python
implementation and no env-var fallback — the wheel is a hard import.

Why now: opt-in defaults don't drive python retirement. Byte-equal
parity was already proven across 27 fixtures (stage 3a); keeping a
shadow python impl behind a flag is a permanent maintenance cost with
no operational benefit. Stage 3b deletes ~700 lines of python parser /
scorer / formatter code; the rust crate has its own coverage.

Surface preserved:
- `headroom.transforms.diff_compressor.DiffCompressor` — same class
  name, same `__init__`, same `compress(content, context)` shape.
  Returns python `DiffCompressionResult` dataclasses so call sites that
  destructure with `asdict()` work unchanged.
- `DiffCompressorConfig` and `DiffCompressionResult` dataclasses kept.
- Sidecar `compress_with_stats(...)` exposes the rust-only
  `DiffCompressorStats` (per-file hunk drops, context lines trimmed,
  file_mode normalizations) for observability.

Removed:
- Python parser / scorer / formatter (~700 lines).
- Internal `DiffHunk` / `DiffFile` parser dataclasses (rust crate has
  parallel coverage).
- 12 tests that probed `_parse_diff` / `_score_hunks` or the deleted
  parser dataclasses. The 29 public-API tests in `test_diff_compressor.py`
  remain and now exercise the rust backend through the same import path.
- `HEADROOM_DIFF_COMPRESSOR_BACKEND` env var — no longer meaningful.

Build:
- `scripts/build_rust_extension.sh` runs `maturin develop` and symlinks
  the built `.so` into `headroom/` so `import headroom._core` resolves
  past the in-tree package shadowing the maturin overlay.
- `.gitignore` excludes the symlinks and allowlists the build script.

Tests:
- 544 transforms pass; 33 rust-vs-fixture parity tests guard the pyo3
  bridge against regressions (`tests/test_transforms/test_diff_compressor_rust_parity.py`).
- Mypy clean.
2026-04-26 09:15:37 -07:00
..
headroom-core fix(diff): close ContentRouter routing gaps for merge diffs and long preambles 2026-04-26 09:13:08 -07:00
headroom-parity refactor(rust): diff_compressor — surface hidden cutoffs + lossy-emit stats 2026-04-26 09:13:08 -07:00
headroom-proxy ci: fix cargo fmt + maturin action invocation 2026-04-25 12:52:55 -07:00
headroom-py feat(rust): retire python diff_compressor, ship rust-only via pyo3 2026-04-26 09:15:37 -07:00