CI fails on pull requests whose changes are already on main ("No changed files to classify") #109

From 2e19a0b03e404d92d49041a4821b7f78f805d861 Mon Sep 17 00:00:00 2001
From: "Cratis Stagehand (AI)" <stagehand-ai@users.noreply.github.com>
Date: Mon, 28 Sep 2026 05:19:22 +0000
Subject: [PATCH 1/2] Add a change classifier that reports an empty diff as no
 changes

The CI change-detection lived inline in the workflow and exited 2 when the
diff came back empty, which reds the run for a pull request whose changes
are already on the base branch. Move the classification into a script that
resolves both ends before diffing, keeps exit 2 for a base it cannot resolve
or diff, and reports an empty diff as the verdict 'nothing changed' with a
new empty output. A self-test seeds both cases so the fuse cannot rot.
---
 package.json                      |   3 +-
 scripts/classify-changes.sh       |  86 ++++++++++++++++
 scripts/classify-changes.test.mjs | 163 ++++++++++++++++++++++++++++++
 3 files changed, 251 insertions(+), 1 deletion(-)
 create mode 100755 scripts/classify-changes.sh
 create mode 100644 scripts/classify-changes.test.mjs

diff --git a/package.json b/package.json
index 0951da4..3403f8d 100644
--- a/package.json
+++ b/package.json
@@ -42,11 +42,12 @@
     "check:fetch:bun": "node scripts/check-fetch-bun.mjs",
     "check:fetch:next": "node scripts/check-fetch-next.mjs",
     "check:node-test": "node --test scripts/check-node-test.test.mjs",
+    "check:changes:self-test": "node --test scripts/classify-changes.test.mjs",
     "check:observability-recipes": "node scripts/check-observability-recipes.mjs",
     "set-version": "node scripts/set-version.mjs",
     "test": "vitest run",
     "specs": "yarn test",
-    "ci": "yarn tsc -b Source/Core Source/Testing Source/Chronicle Source/Tools/ProxyGenerator && yarn check:metadata && yarn workspace @cratis/arc.core.sample.tasks generate-proxies && yarn workspace @cratis/arc.sample.library generate-proxies && yarn check:proxies && yarn build && yarn check:declarations && yarn check:declarations:self-test && yarn check:consumers && yarn check:fetch && yarn check:node-test && yarn check:observability-recipes && yarn workspace @cratis/arc.sample.library.web build && yarn lint && yarn typecheck && yarn lint:tasks:arc && yarn test:client-generation:verify && yarn test && yarn workspace @cratis/arc.sample.library test:e2e && yarn test:legacy-decorators && yarn test:decorator-types && yarn docs:lint && yarn docs:snippets:self-test && yarn docs:snippets && yarn docs:examples:self-test && yarn docs:examples && node --test scripts/for_release/*.test.mjs && yarn set-version --check"
+    "ci": "yarn tsc -b Source/Core Source/Testing Source/Chronicle Source/Tools/ProxyGenerator && yarn check:metadata && yarn workspace @cratis/arc.core.sample.tasks generate-proxies && yarn workspace @cratis/arc.sample.library generate-proxies && yarn check:proxies && yarn build && yarn check:declarations && yarn check:declarations:self-test && yarn check:consumers && yarn check:fetch && yarn check:node-test && yarn check:changes:self-test && yarn check:observability-recipes && yarn workspace @cratis/arc.sample.library.web build && yarn lint && yarn typecheck && yarn lint:tasks:arc && yarn test:client-generation:verify && yarn test && yarn workspace @cratis/arc.sample.library test:e2e && yarn test:legacy-decorators && yarn test:decorator-types && yarn docs:lint && yarn docs:snippets:self-test && yarn docs:snippets && yarn docs:examples:self-test && yarn docs:examples && node --test scripts/for_release/*.test.mjs && yarn set-version --check"
   },
   "devDependencies": {
     "@cratis/arc.react": "22.19.1",
diff --git a/scripts/classify-changes.sh b/scripts/classify-changes.sh
new file mode 100755
index 0000000..abb4734
--- /dev/null
+++ b/scripts/classify-changes.sh
@@ -0,0 +1,86 @@
+#!/usr/bin/env bash
+# Copyright (c) Cratis. All rights reserved.
+# Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+# Classifies the files changed between a base ref and HEAD for the CI workflow.
+#
+# Usage: classify-changes.sh [<base-sha>] [<head-ish>]
+#
+# The base may also be passed through the BASE environment variable. Writes
+# code=, drizzle= and empty= lines to $GITHUB_OUTPUT when it is set, and to
+# stdout otherwise. Exit codes follow the repository convention: 0 classified,
+# 2 could not run.
+
+set -euo pipefail
+
+base=${1:-${BASE:-}}
+head=${2:-HEAD}
+
+# Machine-readable outputs; human-readable progress goes through say() so that
+# stdout stays parseable whenever the outputs do not go to $GITHUB_OUTPUT.
+emit() {
+    if [[ -n "${GITHUB_OUTPUT:-}" ]]; then
+        printf '%s\n' "$1" >>"$GITHUB_OUTPUT"
+    else
+        printf '%s\n' "$1"
+    fi
+}
+
+say() {
+    if [[ -n "${GITHUB_OUTPUT:-}" ]]; then
+        printf '%s\n' "$1"
+    else
+        printf '%s\n' "$1" >&2
+    fi
+}
+
+if [[ -z "$base" || "$base" =~ ^0+$ ]]; then
+    say 'No base to diff against; running every gate'
+    emit 'code=true'
+    emit 'drizzle=true'
+    emit 'empty=false'
+    exit 0
+fi
+
+# Resolve both ends first, so a missing base is reported as "could not run"
+# rather than being read as an empty diff and skipping every gate.
+if ! base_commit=$(git rev-parse -q --verify "$base^{commit}") ||
+    ! head_commit=$(git rev-parse -q --verify "$head^{commit}"); then
+    say "Cannot resolve $base or $head in this checkout"
+    exit 2
+fi
+
+if ! files=$(git diff --name-only "$base_commit" "$head_commit"); then
+    say "Cannot diff $base_commit against $head_commit"
+    exit 2
+fi
+
+if [[ -z "$files" ]]; then
+    # Identical trees: everything this ref carries is already in the base, for
+    # instance a change that landed separately. That is the verdict "nothing
+    # changed", not a failure to look, so the gates skip instead of going red.
+    say '::notice::No net changes against the base; skipping the code, docs and Drizzle gates'
+    emit 'code=false'
+    emit 'drizzle=false'
+    emit 'empty=true'
+    exit 0
+fi
+
+code=false
+drizzle=false
+count=0
+while IFS= read -r file; do
+    count=$((count + 1))
+    case "$file" in
+        Source/Drizzle/*|Documentation/sql/observing-postgresql.md|.github/workflows/ci.yml|package.json|yarn.lock) drizzle=true ;;
+    esac
+    case "$file" in
+        Documentation/*|*.md) ;;
+        *) code=true ;;
+    esac
+done <<<"$files"
+
+say "Classified $count changed file(s): code=$code drizzle=$drizzle"
+emit "code=$code"
+emit "drizzle=$drizzle"
+emit 'empty=false'
diff --git a/scripts/classify-changes.test.mjs b/scripts/classify-changes.test.mjs
new file mode 100644
index 0000000..0695e7e
--- /dev/null
+++ b/scripts/classify-changes.test.mjs
@@ -0,0 +1,163 @@
+// Copyright (c) Cratis. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+import assert from 'node:assert/strict';
+import { spawnSync } from 'node:child_process';
+import { mkdtempSync, mkdirSync, readFileSync, rmSync, writeFileSync } from 'node:fs';
+import { tmpdir } from 'node:os';
+import { dirname, join } from 'node:path';
+import { test } from 'node:test';
+import { fileURLToPath } from 'node:url';
+
+const script = fileURLToPath(new URL('./classify-changes.sh', import.meta.url));
+
+const tracked = {
+    'Documentation/index.md': '# Arc\n',
+    'Documentation/sql/observing-postgresql.md': '# Observing PostgreSQL\n',
+    '.github/workflows/ci.yml': 'name: CI\n',
+    'package.json': '{}\n',
+    'yarn.lock': '# yarn.lock\n',
+    'Source/Core/index.ts': 'export {};\n',
+    'Source/Drizzle/index.ts': 'export {};\n'
+};
+
+const drizzleTriggers = [
+    'Source/Drizzle/index.ts',
+    'Documentation/sql/observing-postgresql.md',
+    '.github/workflows/ci.yml',
+    'package.json',
+    'yarn.lock'
+];
+
+function git(folder, ...arguments_) {
+    const result = spawnSync('git', ['-C', folder, ...arguments_], { encoding: 'utf8' });
+    assert.equal(result.status, 0, `git ${arguments_.join(' ')} failed: ${result.stderr}`);
+    return result.stdout.trim();
+}
+
+function commit(folder, message) {
+    git(folder, 'add', '-A');
+    git(folder, 'commit', '--quiet', '--allow-empty', '--message', message);
+    return git(folder, 'rev-parse', 'HEAD');
+}
+
+function repository(t) {
+    const folder = mkdtempSync(join(tmpdir(), 'arc-classify-changes-'));
+    t.after(() => rmSync(folder, { recursive: true, force: true }));
+    for (const [file, content] of Object.entries(tracked)) {
+        mkdirSync(dirname(join(folder, file)), { recursive: true });
+        writeFileSync(join(folder, file), content);
+    }
+    git(folder, 'init', '--initial-branch=main');
+    git(folder, 'config', 'user.email', 'ci@cratis');
+    git(folder, 'config', 'user.name', 'CI');
+    commit(folder, 'Initial state');
+    return folder;
+}
+
+function edit(folder, file, content = `${tracked[file] ?? ''}# changed\n`) {
+    mkdirSync(dirname(join(folder, file)), { recursive: true });
+    writeFileSync(join(folder, file), content);
+}
+
+function change(folder, file, content) {
+    const base = git(folder, 'rev-parse', 'HEAD');
+    edit(folder, file, content);
+    commit(folder, `Touch ${file}`);
+    return base;
+}
+
+function classify(folder, base) {
+    return spawnSync('bash', [script, ...(base === undefined ? [] : [base])], {
+        cwd: folder,
+        encoding: 'utf8'
+    });
+}
+
+function outputs(result) {
+    return Object.fromEntries(result.stdout.trim().split('\n').filter(Boolean).map(line => line.split('=')));
+}
+
+test('runs every gate when no base is available', t => {
+    const folder = repository(t);
+    const result = classify(folder);
+    assert.equal(result.status, 0, result.stderr);
+    assert.deepEqual(outputs(result), { code: 'true', drizzle: 'true', empty: 'false' });
+});
+
+test('runs every gate when the base is the all-zero sha', t => {
+    const folder = repository(t);
+    const result = classify(folder, '0'.repeat(40));
+    assert.equal(result.status, 0, result.stderr);
+    assert.deepEqual(outputs(result), { code: 'true', drizzle: 'true', empty: 'false' });
+});
+
+test('classifies a documentation-only change as docs-only', t => {
+    const folder = repository(t);
+    const base = change(folder, 'Documentation/index.md');
+    const result = classify(folder, base);
+    assert.equal(result.status, 0, result.stderr);
+    assert.deepEqual(outputs(result), { code: 'false', drizzle: 'false', empty: 'false' });
+});
+
+test('classifies a source change as a code change', t => {
+    const folder = repository(t);
+    const base = change(folder, 'Source/Core/index.ts');
+    const result = classify(folder, base);
+    assert.equal(result.status, 0, result.stderr);
+    assert.deepEqual(outputs(result), { code: 'true', drizzle: 'false', empty: 'false' });
+});
+
+for (const file of drizzleTriggers) {
+    test(`classifies a change to ${file} as Drizzle-affecting`, t => {
+        const folder = repository(t);
+        const base = change(folder, file);
+        const result = classify(folder, base);
+        assert.equal(result.status, 0, result.stderr);
+        // Only the documented SQL page is documentation; the other triggers are code paths.
+        const code = !file.startsWith('Documentation/');
+        assert.deepEqual(outputs(result), { code: `${code}`, drizzle: 'true', empty: 'false' });
+    });
+}
+
+test('classifies an already-landed change as empty and skips every gate', t => {
+    const folder = repository(t);
+    const snippet = 'Documentation/client-snippets/scenarios/use-current-state-in-a-command/seed-events.md';
+    edit(folder, snippet, '# Snippet\n');
+    const fork = commit(folder, 'Add the seed-events snippet');
+    // The branch departs before main drops the snippet and re-applies the same drop.
+    git(folder, 'checkout', '--quiet', '-b', 'topic', fork);
+    rmSync(join(folder, snippet));
+    commit(folder, 'Drop the seed-events snippet on the branch');
+    git(folder, 'checkout', '--quiet', 'main');
+    rmSync(join(folder, snippet));
+    const base = commit(folder, 'Drop the seed-events snippet on main');
+    git(folder, 'merge', '--quiet', '--no-ff', '--message', 'Merge the branch into main', 'topic');
+    const result = classify(folder, base);
+    assert.equal(result.status, 0, result.stderr);
+    assert.deepEqual(outputs(result), { code: 'false', drizzle: 'false', empty: 'true' });
+});
+
+test('writes the outputs to GITHUB_OUTPUT and keeps stdout for the log', t => {
+    const folder = repository(t);
+    const scratch = mkdtempSync(join(tmpdir(), 'arc-classify-output-'));
+    t.after(() => rmSync(scratch, { recursive: true, force: true }));
+    const githubOutput = join(scratch, 'output');
+    const base = change(folder, 'Source/Core/index.ts');
+    const result = spawnSync('bash', [script, base], {
+        cwd: folder,
+        encoding: 'utf8',
+        env: { ...process.env, GITHUB_OUTPUT: githubOutput }
+    });
+    assert.equal(result.status, 0, result.stderr);
+    assert.match(result.stdout, /Classified 1 changed file\(s\): code=true drizzle=false/);
+    assert.deepEqual(readFileSync(githubOutput, 'utf8').trim().split('\n'),
+        ['code=true', 'drizzle=false', 'empty=false']);
+});
+
+test('reports an unresolvable base as could-not-run instead of skipping the gates', t => {
+    const folder = repository(t);
+    const result = classify(folder, 'f'.repeat(40));
+    assert.equal(result.status, 2);
+    assert.match(result.stderr, /Cannot resolve/);
+});
-- 
2.43.0


From 0f64dd322f347f71673a1c05a430139447965fdd Mon Sep 17 00:00:00 2001
From: "Cratis Stagehand (AI)" <stagehand-ai@users.noreply.github.com>
Date: Mon, 28 Sep 2026 05:19:31 +0000
Subject: [PATCH 2/2] Stop the CI changes job failing on pull requests with no
 net changes

A pull request whose changes already landed on the base branch produces a
merge ref whose tree is identical to the base, so the classify step found
no changed files and exited 2, failing the run (run 36380119330, PR #108).
Run the classifier script instead and skip the docs gate when it reports an
empty diff, so an already-landed change skips every gate instead of going
red.
---
 .github/workflows/ci.yml | 28 +++-------------------------
 1 file changed, 3 insertions(+), 25 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index d663d37..99b8e35 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -23,6 +23,7 @@ jobs:
     outputs:
       code: ${{ steps.classify.outputs.code }}
       drizzle: ${{ steps.classify.outputs.drizzle }}
+      empty: ${{ steps.classify.outputs.empty }}
     steps:
       - name: Check out code
         uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
@@ -33,34 +34,11 @@ jobs:
         id: classify
         env:
           BASE: ${{ github.event.pull_request.base.sha || github.event.before }}
-        run: |
-          if [[ "${{ github.event_name }}" == workflow_dispatch || "$BASE" =~ ^0+$ ]]; then
-            echo 'code=true' >> "$GITHUB_OUTPUT"
-            echo 'drizzle=true' >> "$GITHUB_OUTPUT"
-            exit 0
-          fi
-          files=$(git diff --name-only "$BASE" HEAD)
-          if [[ -z "$files" ]]; then
-            echo 'No changed files to classify' >&2
-            exit 2
-          fi
-          code=false
-          drizzle=false
-          while IFS= read -r file; do
-            case "$file" in
-              Source/Drizzle/*|Documentation/sql/observing-postgresql.md|.github/workflows/ci.yml|package.json|yarn.lock) drizzle=true ;;
-            esac
-            case "$file" in
-              Documentation/*|*.md) ;;
-              *) code=true ;;
-            esac
-          done <<< "$files"
-          echo "code=$code" >> "$GITHUB_OUTPUT"
-          echo "drizzle=$drizzle" >> "$GITHUB_OUTPUT"
+        run: bash scripts/classify-changes.sh "$BASE"
 
   docs:
     needs: changes
-    if: needs.changes.outputs.code == 'false'
+    if: needs.changes.outputs.code == 'false' && needs.changes.outputs.empty == 'false'
     runs-on: ubuntu-latest
     timeout-minutes: 30
     steps:
-- 
2.43.0