RustPython · moreal · Sep 6, 2026 · Sep 6, 2026 · Sep 6, 2026 · Sep 6, 2026
diff --git a/.github/workflows/codspeed-comment.yaml b/.github/workflows/codspeed-comment.yaml
@@ -0,0 +1,65 @@
+on:
+  workflow_run:
+    workflows: [CodSpeed]
+    types: [completed]
+
+name: CodSpeed local diff comment
+
+# `pull_request` from a fork carries a read-only token no matter what is
+# granted here, so the diff itself is computed in that read-only job and
+# handed off as an artifact; this workflow runs in the base repo's context
+# (`workflow_run` always does, regardless of which fork triggered it) and is
+# the one trusted with a token that can write the comment.
+permissions:
+  contents: read
+  pull-requests: write
+
+jobs:
+  comment:
+    if: ${{ github.event.workflow_run.conclusion == 'success' }}
+    runs-on: ubuntu-latest
+    steps:
+      - name: Download the diff produced by the CodSpeed workflow
+        uses: actions/download-artifact@3e5f45b2cfb9172054b4087a40e8e0b5a5461e7c # v8.0.1
+        with:
+          name: codspeed-local-diff
+          run-id: ${{ github.event.workflow_run.id }}
+          github-token: ${{ github.token }}
+        continue-on-error: true # the artifact is absent on push/merge_group runs
+
+      - name: Post or update the PR comment
+        uses: actions/github-script@d746ffe35508b1917358783b479e04febd2b8f71 # v9.0.0
+        with:
+          script: |
+            const fs = require('fs');
+            if (!fs.existsSync('diff.md') || !fs.existsSync('pr_number.txt')) {
+              core.info('No diff.md/pr_number.txt in this run; nothing to comment.');
+              return;
+            }
+
+            const prNumber = parseInt(fs.readFileSync('pr_number.txt', 'utf8').trim(), 10);
+            const body = fs.readFileSync('diff.md', 'utf8');
+            const marker = '<!-- codspeed-local-diff -->';
+
+            const comments = await github.paginate(github.rest.issues.listComments, {
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              issue_number: prNumber,
+            });
+            const existing = comments.find((c) => c.body && c.body.includes(marker));
+
+            if (existing) {
+              await github.rest.issues.updateComment({
+                owner: context.repo.owner,
+                repo: context.repo.repo,
+                comment_id: existing.id,
+                body,
+              });
+            } else {
+              await github.rest.issues.createComment({
+                owner: context.repo.owner,
+                repo: context.repo.repo,
+                issue_number: prNumber,
+                body,
+              });
+            }
diff --git a/.github/workflows/codspeed.yaml b/.github/workflows/codspeed.yaml
@@ -112,3 +112,106 @@ jobs:
         with:
           path: build/codspeed-environment-reference.json
           key: codspeed-environment-${{ runner.os }}-${{ runner.arch }}-${{ github.run_id }}
+
+  local-diff:
+    # PR-only: base and head are measured back-to-back in this one job so
+    # they share the exact runner, sidestepping the cross-machine noise
+    # `scripts/codspeed-local-diff.py` documents. See `scripts/codspeed-local-diff.py`
+    # for why this exists alongside the CodSpeedHQ-reported numbers above.
+    if: ${{ github.event_name == 'pull_request' && !contains(github.event.pull_request.labels.*.name, 'skip:ci') }}
+    name: Local base/head diff
+    runs-on: ubuntu-latest
+    timeout-minutes: 60
+    permissions:
+      contents: read
+    env:
+      CACHE_PATHS: |
+        ~/.cargo/.crates2.json
+        ~/.cargo/.crates.toml
+        ~/.cargo/bin/
+        ~/.cargo/registry/index/
+        ~/.cargo/registry/cache/
+        ~/.cargo/git/db/
+        target/
+    steps:
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          ref: ${{ github.event.pull_request.head.sha }}
+          fetch-depth: 0
+          persist-credentials: false
+
+      - uses: dtolnay/rust-toolchain@stable
+
+      # The benchmarks are linked against libpython through the pyo3 dev-dependency.
+      - uses: actions/setup-python@5fda3b95a4ea91299a34e894583c3862153e4b97 # v7.0.0
+
+      # The bench binaries `cargo codspeed build` produces only report real
+      # instruction counts when driven by the `codspeed` CLI's runner
+      # protocol (see scripts/codspeed-local-diff.py) -- installed the same
+      # way CodSpeedHQ/action does, pinned to the version that action uses
+      # below.
+      - name: Install the codspeed CLI
+        run: curl -fsSL https://codspeed.io/v5.2.1/install.sh | bash -s -- --quiet
+
+      # For `callgrind_annotate` only, to total up a run's instruction count
+      # (see scripts/codspeed-local-diff.py) -- the codspeed CLI installs
+      # its own patched Valgrind for the measurement itself.
+      - name: Install valgrind (for callgrind_annotate)
+        run: sudo apt-get update && sudo apt-get install -y --no-install-recommends valgrind
+
+      - name: Restore cache
+        uses: actions/cache/restore@55cc8345863c7cc4c66a329aec7e433d2d1c52a9 # v6.1.0
+        with:
+          path: ${{ env.CACHE_PATHS }}
+          key: codspeed-v2-${{ hashFiles('**/Cargo.lock') }}
+          restore-keys: codspeed-v2-
+        continue-on-error: true
+
+      - name: Install cargo-codspeed
+        run: cargo install cargo-codspeed --locked --version ^5
+
+      # The base commit predates this script's own addition to the repo, so
+      # `git checkout <base sha>` below would delete it from disk; run it
+      # from a copy outside the worktree instead.
+      - name: Copy the diff script out of the checkout
+        run: cp scripts/codspeed-local-diff.py "${RUNNER_TEMP}/codspeed-local-diff.py"
+
+      - name: Build head benchmark targets
+        run: cargo codspeed build --locked --measurement-mode simulation -p rustpython -p rustpython-sre_engine
+
+      - name: Measure head
+        run: python3 "${RUNNER_TEMP}/codspeed-local-diff.py" measure --out results/head
+
+      - name: Check out base commit
+        # Reuses the same `target/` build cache, so only what changed since
+        # the base commit needs recompiling.
+        run: git checkout --quiet "${{ github.event.pull_request.base.sha }}" --
+
+      - name: Build base benchmark targets
+        run: cargo codspeed build --locked --measurement-mode simulation -p rustpython -p rustpython-sre_engine
+
+      - name: Measure base
+        run: python3 "${RUNNER_TEMP}/codspeed-local-diff.py" measure --out results/base
+
+      - name: Restore head commit
+        if: always()
+        run: git checkout --quiet "${{ github.event.pull_request.head.sha }}" --
+
+      - name: Compute diff
+        run: |
+          python3 "${RUNNER_TEMP}/codspeed-local-diff.py" diff \
+            --base results/base --head results/head \
+            --md diff.md --json diff.json
+          echo "${{ github.event.pull_request.number }}" > pr_number.txt
+
+      - name: Upload diff artifact
+        if: always()
+        uses: actions/upload-artifact@043fb46d1a93c77aae656e7c1c64a875d1fc6a0a # v7.0.1
+        with:
+          name: codspeed-local-diff
+          path: |
+            diff.md
+            diff.json
+            pr_number.txt
+          retention-days: 14
+          if-no-files-found: ignore