[cknitt]

Removes the Rust build system. rescript has run the OCaml build system since 13.0.0-alpha.7, and rescript-rust only shipped for comparison.

Commits

1. Check rewatch output against snapshots instead of Rust rewatch. The rewatch-ocaml/tests/check_*.sh scripts used to run Rust and OCaml side by side. Now they run rescript alone:

   • Config acceptance: each case keeps its expected accept/reject. The argument comparison became one snapshot (snapshots/config_acceptance/arguments.txt).
   • Command validation: the Rust-vs-OCaml output comparisons became 24 snapshots.
   • Verbose output: three event snapshots.
   • Interactive output: it already had exact expectations for every phase, so the Rust comparisons were simply dropped.
   • Snapshot helper: check_snapshot (in test_helpers.sh, with check_snapshot.js) replaces root paths with placeholders and normalizes CRLF and backslashes, so one snapshot serves Unix and Windows. UPDATE_SNAPSHOTS=1 rewrites the snapshots.
   • Checked against Rust: before Rust was removed, the converted scripts were also run against the Rust executable, and every snapshot matched its output.
   • Dropped cases: only the three missing-RESCRIPT_BSC_EXE cases, which tested a Rust-only variable.

2. Remove the Rust build system:

   • rewatch/src, Cargo files, rustfmt.toml, and Rust agent docs.
   • The rescript-rust bin and launcher (package.json, platform packages, artifacts.json).
   • The Cargo rules in the Makefile (rewatch, test-rewatch-rust, clean-rewatch).
   • The build-rewatch CI action, copyExes.js, and the Rust reference suite run.
   • Rust formatting, the Cargo version constraint, and the Rust base image and extension in the dev container.
   • The Rust/OCaml performance gates in rewatch-ocaml/bench.

   rewatch/ keeps the integration suite and the behavior docs. rewatch-ocaml/ is not renamed in this PR; the directory name is still open. Comments, test names, and READMEs no longer refer to Rust. The README's "Differences from Rust rewatch" section became behavior notes.

Review guide

• Windows snapshots: command validation now compares against snapshots on Windows too. Normalization covers native long and short paths, CRLF, and separators, but only Windows CI shows whether that is enough.
• Bench removal: the bench scripts were acceptance gates against Rust ("OCaml ≤ 125% of Rust"). They could come back later as a baseline-vs-candidate comparison of two rescript builds.

🤖 Generated with Claude Code

https://claude.ai/code/session_01Kbf3gHBNSg9dHsEnBuQaPf

[github-actions]

Changelog

💥 Breaking Change

• Remove the Rust build system rescript-rust; use rescript. Building the compiler no longer needs a Rust toolchain.

💅 Polish

• rescript --filter accepts any Perl-style regular expression the build system can match, instead of only the subset that also meant the same in the Rust build system.

Semantic Diff

8 commits · Full page

Check rewatch output against snapshots instead of Rust rewatch

_{06d6bb5 · cknitt + Claude · Nov 05, 2026, 17:08 UTC}

The check_*.sh scripts compared the OCaml build system with the Rust one, which is about to be removed. They now run rescript alone: each case keeps its expected outcome, and output the scripts used to compare with Rust's is compared with snapshots under rewatch-ocaml/tests/snapshots, written with UPDATE_SNAPSHOTS=1. Paths are replaced by placeholders, line endings and separators normalized, so one snapshot serves Unix and Windows.

Review

• Do the snapshots still describe Rust's output? Yes: before removing Rust, every snapshot was checked against the Rust executable too; the verbose, interactive and command-validation snapshots match it. Remaining differences are the documented ones, whose cases already expected OCaml's outcome.
• Which checks were dropped? Only Rust-only ones: the three missing-RESCRIPT_BSC_EXE cases (OCaml ignores the variable), Rust's exit codes and error wording. Config cases named for Rust's last-key-wins behavior (duplicate-last) were renamed, since duplicates are rejected.

Remove the Rust build system

_{8789a23 · cknitt + Claude · Nov 05, 2026, 17:08 UTC}

rescript has run the OCaml build system since 13.0.0-alpha.7; the Rust implementation only shipped as rescript-rust for comparison. This removes its sources, the rescript-rust executable and launcher, the Cargo build in the Makefile and CI, the Rust/OCaml performance gates, Rust formatting and version constraints, and the Rust toolchain from the dev container. rewatch/ keeps the integration suite and the behavior documents; the implementation stays in rewatch-ocaml/.

⚠️ Breaking: rescript-rust and its RESCRIPT_BSC_EXE override are gone; use rescript, which has the compiler built in.

Make the command-validation snapshots hold in CI

_{70a6242 · cknitt + Claude · Nov 05, 2026, 18:23 UTC}

CI sets CLICOLOR_FORCE=1, which colored the redirected-output cases, so the script now unsets it. On Windows the runner's TEMP is an 8.3 short path, so check_snapshot also replaces the explicit long spelling that bsc prints.

Sort verbose events in the C locale

_{0c1b07d · cknitt + Claude · Nov 05, 2026, 18:34 UTC}

macOS CI sorts with a locale that puts compile dirty: before DEBUG:, so the sorted events did not match the snapshot written in the C locale.

Normalize escaped Windows paths in snapshots

_{e93d828 · cknitt + Claude · Nov 05, 2026, 18:39 UTC}

Some diagnostics print a path as a quoted string, so on Windows its backslashes are doubled (C:\\Users\\...). check_snapshot now replaces that spelling of each root and turns escaped separators into slashes as well.

Keep backslashes in Unix snapshots and share path normalization

_{ab6306d · cknitt + Claude · Nov 05, 2026, 19:23 UTC}

Review of #9238: check_snapshot turned every backslash into a slash, so a snapshot could not hold an escape such as \n, and a path printed with backslashes on Unix went unnoticed. It now rewrites separators on Windows only. The command-validation checks that grep for paths (normalize_project_path, require_error_contains) use the same normalization through the new normalize_paths helper, instead of deriving short paths from USERPROFILE.

Drop the remaining Rust settings from rewatch tests

_{09736cb · cknitt + Claude · Nov 05, 2026, 19:23 UTC}

Review of #9238: the integration tests still set RUST_BACKTRACE and RAYON_NUM_THREADS, which rescript ignores. The two tests that ran Rust on one thread now set REWATCH_COMPILER_DOMAINS=1, so they again check scheduling with a single compiler worker. Comments shortened when the Rust mentions were removed are rewrapped.

✨ Accept every regular expression Re can match in --filter

_{290323e · cknitt + Claude · Nov 05, 2026, 19:45 UTC · new}

--filter rejected valid Perl constructs, such as \Q...\E, \Z and [z-a], because Rust's regex crate read them differently. With the Rust build system gone, that parity check only refuses valid filters, so the filter now accepts what Re's Perl syntax parses and still rejects what Re cannot match, such as backreferences.

[cknitt]

@codex review

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-11-05T18:37:36.285045Z	70a6242	Manual request

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[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. 🚀

Reviewed commit: 70a624238c

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