feat: add lake check as a comparator frontend - #14885
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lake check as a leanchecker/comparator frontendlake check as a comparator frontend
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August 24, 2026 13:55
This PR ships the Lean NDJSON exporter as a new `leanexport` toolchain binary and vendors the proof-comparison libraries of [Comparator](https://github.com/leanprover/comparator) into Lake. There is no user-visible behavior change yet; `lake challenge` follows. The exporter lands under a single `LeanExport` module prefix (`src/LeanExport.lean` plus `src/LeanExport/{Basic,Parse}.lean`) and is built like `leanchecker`/`leanir`. Since `Lake.Check` imports `LeanExport.Parse`, `libLake_shared` additionally links `libLeanExport.a.export`; the archive is linked without `--whole-archive` so the exporter's `main` stays out of the shared library. `tests/lake/lakefile.toml`, which builds Lake standalone, gains a matching `LeanExport` library for the same reason. Every vendored file is byte-identical to its upstream source once the module header and the `LeanExport`/`Lake.Check` namespace wrapper are removed, so the diff can be checked mechanically rather than read. The sources are `lean4export` at `3de59f10` and Comparator at `8d84e678`. `leanexport` accordingly produces byte-identical output to upstream `lean4export` built against the same toolchain. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
This PR vendors Comparator's `Main.lean` as `Lake/CLI/Check.lean`. There is no user-visible behavior change: nothing calls it yet, and `lake check` follows in the next commit. The code is transliterated rather than rewritten, so that it diffs cleanly against upstream: only the module header, the `Lake.Check` namespace, the `LeanExport` names and `Kernel.Environment.replay` (which `Environment.replay` is now deprecated in favor of) differ. The executable `main` is dropped, since this is a library module. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
This PR ships Comparator as `lake challenge`, so judging a solution no longer means cloning a repository, matching its toolchain to the one that built the `.olean` files, and hand-writing the wiring: a challenge author distributes the project and its configuration, and a solver runs one command. `landrun` remains a hard requirement with no unsandboxed mode, so the command is available on Linux only. The configuration is Comparator's, unchanged, passed with `--config`. Exit codes now split three ways instead of raising a `userError` for everything: 2 for failing to start at all, such as a missing `landrun` or a configuration that is absent or malformed, and 1 for a rejected solution, so that a caller can tell an environment problem from a judgment. `lean4export` becomes the `leanexport` toolchain binary, so third-party checkers can keep using it standalone, and Comparator's libraries land under `Lake.Check`. Both are vendored from `lean4export` at `3de59f10` and Comparator at `4c921f7ab3ce`, byte-identical to their sources once the module header and the namespace wrapper are removed, so that part of the diff can be checked mechanically rather than read. `leanexport` accordingly produces byte-identical output to upstream built against the same toolchain. The commits separate the vendoring from the changes: the libraries, then Comparator's `Main.lean` as `Lake/CLI/Check.lean` wired to nothing, then the departures from that baseline, so that the third diff is the review surface. Those departures are the exit codes above; `LeanInstall.sysroot`, `LakeInstall.lake` and the bundled `leanexport` in place of `PATH` lookups, which removes a weak link inside the sandbox; `LEAN_PATH` taken from the loaded workspace rather than requiring a `lake env` wrapper; and a `git` lookup that reports absence instead of throwing. `COMPARATOR_LEAN4EXPORT` is deliberately not honored. The export format has to match the compiler that produced the `.olean` files, which is exactly the pinning this change removes, so honoring a stale setting from an existing CI configuration would quietly reintroduce it. `COMPARATOR_LANDRUN` and `COMPARATOR_NANODA` keep working, since neither tool is bundled. Comparator's test projects become `tests/lake/tests/check-*`, along with its `fake-landrun.sh` stand-in, which the tests select through `COMPARATOR_LANDRUN` since Landlock cannot be assumed available in CI containers. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
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August 25, 2026 17:15
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This PR ships
lake checkas a frontend tocomparator, significantly simplifying its setup.landrunremains a hard requirement with no unsandboxed mode, so the command is available on Linux only for now.The configuration is unchanged from comparator, passed with
--config. Exit codes have become more fine-grained: 2 for failing to start at all, such as a missinglandrunor a configuration that is absent or malformed, and 1 for a rejected solution, so that a caller can tell an environment problem from a judgment.lean4exportbecomes theleanexporttoolchain binary, vendored at3de59f10, and comparator's libraries land underLake.Check(no separate executable), vendored at4c921f7ab3ce.To follow: additional checking modes and configurations.