feat(ci): add cargo-crap check to CI

.cargo-crap.toml

@@ -0,0 +1,16 @@
+threshold = 30
+fail-above = true
+min = 30
+missing = "pessimistic"
+# Suppress non-shipped code so the gate only measures real library logic.
+# NOTE: must use `allow` (matches a function's defining file) rather than
+# `exclude` (filesystem-walk only — does not filter functions read from the
+# lcov file). Globs match absolute paths, hence the `**/` prefixes.
+allow = [
+    "**/cot-codegen/**",       # generated AST/codegen helpers
+    "**/cot-macros/**",        # proc-macro implementations
+    "**/tests/**",             # integration & e2e test code
+    "**/src/test.rs",          # in-crate test utilities (TestDatabase, etc.)
+    "**/src/test_utils.rs",    # in-crate test helpers
+    "**/examples/**",          # example applications
+]

.github/workflows/rust.yml

@@ -245,6 +245,69 @@
         env:
           CODECOV_TOKEN: ${{ secrets.CODECOV_TOKEN }}
 
+      - name: Generate lcov report for cargo-crap
+        run: cargo llvm-cov report --lcov --output-path lcov.info
+
+      - name: Upload lcov artifact
+        uses: actions/upload-artifact@v4
+        with:
+          # Unique per workflow run so concurrent PR runs never collide.
+          name: lcov-${{ github.run_id }}
+          path: lcov.info
+          retention-days: 1
+
+  cargo-crap:
+    if: github.event_name == 'push' || github.event_name == 'schedule' || github.event.pull_request.head.repo.full_name != github.repository
+
+    name: CRAP metric gate
+    runs-on: ubuntu-latest
+    needs: ["coverage"]
+    env:
+      RUSTC_WRAPPER: ""
+      SCCACHE_GHA_ENABLED: ""
+    steps:
+      - name: Checkout source
+        uses: actions/checkout@v6
+
+      - name: Download lcov artifact
+        uses: actions/download-artifact@v4
+        with:
+          name: lcov-${{ github.run_id }}
+          path: lcov
+
+      - name: Install cargo-crap
+        uses: taiki-e/install-action@v2
+        with:
+          tool: cargo-crap
+
+      - name: Run cargo-crap
+        run: cargo crap --lcov lcov/lcov.info --workspace --fail-above --format pr-comment --output crap-comment.md
+
+      - name: Post or update PR comment
+        if: github.event_name == 'pull_request'
+        uses: actions/github-script@v7
+        with:
+          script: |
+            const fs = require('fs');
+            const body = fs.readFileSync('crap-comment.md', 'utf8');
+            const marker = '<!-- cargo-crap-report -->';
+            const { data: comments } = await github.rest.issues.listComments({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              issue_number: context.issue.number,
+            });
+            const existing = comments.find(c => c.body.startsWith(marker));
+            const args = {
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              body,
+            };
+            if (existing) {
+              await github.rest.issues.updateComment({ ...args, comment_id: existing.id });
+            } else {
+              await github.rest.issues.createComment({ ...args, issue_number: context.issue.number });
+            }
+
   rustfmt:
     if: github.event_name == 'push' || github.event_name == 'schedule' || github.event.pull_request.head.repo.full_name != github.repository
 

.gitignore

@@ -13,3 +13,7 @@ target/
 *.db
 *.sqlite3
 *.sqlite3-journal
+
+# Coverage / cargo-crap artifacts
+/lcov.info
+/codecov.json

justfile

@@ -43,6 +43,20 @@ coverage:
     # requires cargo-llvm-cov installed and nightly toolchain
     cargo llvm-cov --all-features --workspace --branch --doctests --html --open
 
+alias cr := crap
+
+crap:
+    #!/usr/bin/env bash
+    # compute the CRAP metric the same way CI does (absolute-threshold gate)
+    # requires cargo-llvm-cov + cargo-crap installed and the nightly toolchain
+    set -euxo pipefail
+    docker compose up -d --wait
+    cargo llvm-cov --all-features --workspace --no-report -- --include-ignored
+    cargo llvm-cov --all-features --workspace --doc --no-report
+    cargo llvm-cov report --lcov --output-path lcov.info
+    docker compose down
+    cargo crap --lcov lcov.info --workspace
+
 alias d := docs
 
 docs: