[ops] Remove limits.yml codeownership, add bundle-size PR comment workflow (elastic#270233)

Co-authored-by: kibanamachine <42973632+kibanamachine@users.noreply.github.com>

Author: TamerlanG

.github/CODEOWNERS

@@ -1385,6 +1385,11 @@ x-pack/solutions/workplaceai/test @elastic/workchat-eng
 ##  https://help.github.com/articles/about-codeowners/
 ####
 
+# limits.yml changes frequently as bundle sizes shift; no owner means the ops
+# team isn't auto-requested as reviewer on every bump. A GitHub Actions workflow
+# (bundle-size-limits-comment.yml) flags increases ≥15% instead.
+packages/kbn-optimizer/limits.yml
+
 # The #CC# prefix delineates Code Coverage,
 # used for the 'team' designator within Kibana Stats
 

.github/scripts/bundle_size_limits_comment.js

@@ -0,0 +1,95 @@
+const THRESHOLD = 0.15;
+const MARKER = '<!-- bundle-size-limits-comment -->';
+
+const getContent = async ({ github, context }, ref) => {
+  const { data } = await github.rest.repos.getContent({
+    owner: context.repo.owner,
+    repo: context.repo.repo,
+    path: 'packages/kbn-optimizer/limits.yml',
+    ref,
+  });
+  return Buffer.from(data.content, 'base64').toString('utf8');
+};
+
+const parseYaml = (content) => {
+  const result = {};
+  for (const line of content.split('\n')) {
+    const match = line.match(/^\s{2}(\w+):\s*(\d+)/);
+    if (match) result[match[1]] = parseInt(match[2], 10);
+  }
+  return result;
+};
+
+module.exports = async ({ github, context }) => {
+  const pr = context.payload.pull_request;
+
+  const [baseContent, headContent] = await Promise.all([
+    getContent({ github, context }, pr.base.sha),
+    getContent({ github, context }, pr.head.sha),
+  ]);
+
+  const baseMap = parseYaml(baseContent);
+  const headMap = parseYaml(headContent);
+
+  const bigIncreases = [];
+  for (const [plugin, headSize] of Object.entries(headMap)) {
+    const baseSize = baseMap[plugin];
+    if (baseSize != null && headSize > baseSize) {
+      const pct = (headSize - baseSize) / baseSize;
+      if (pct >= THRESHOLD) {
+        bigIncreases.push({ plugin, baseSize, headSize, pct });
+      }
+    }
+  }
+
+  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 && c.body.includes(MARKER));
+
+  if (bigIncreases.length === 0) {
+    if (existing) {
+      await github.rest.issues.deleteComment({
+        owner: context.repo.owner,
+        repo: context.repo.repo,
+        comment_id: existing.id,
+      });
+    }
+    return;
+  }
+
+  const rows = bigIncreases
+    .sort((a, b) => b.pct - a.pct)
+    .map(
+      ({ plugin, baseSize, headSize, pct }) =>
+        `| \`${plugin}\` | ${baseSize.toLocaleString()} | ${headSize.toLocaleString()} | +${(pct * 100).toFixed(1)}% |`
+    )
+    .join('\n');
+
+  const body =
+    `@${pr.user.login}, this PR increases one or more page-load bundle sizes by 15% or more:\n\n` +
+    `| Plugin | Before (bytes) | After (bytes) | Change |\n` +
+    `|--------|----------------|---------------|--------|\n` +
+    `${rows}\n\n` +
+    `Large bundle size increases can affect page load performance. Consider whether dependencies can be lazy-loaded or code split to reduce the bundle.\n\n` +
+    `See the [bundle optimization guide](https://www.elastic.co/docs/extend/kibana/ci-metrics#ci-metric-resolving-overages) for tips.\n\n` +
+    `${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({
+      issue_number: context.issue.number,
+      owner: context.repo.owner,
+      repo: context.repo.repo,
+      body,
+    });
+  }
+};

.github/workflows/bundle-size-limits-comment.yml

@@ -0,0 +1,31 @@
+name: bundle-size-limits-comment
+
+on:
+  pull_request_target:
+    types:
+      - opened
+      - synchronize
+    paths:
+      - 'packages/kbn-optimizer/limits.yml'
+
+jobs:
+  comment:
+    runs-on: ubuntu-latest
+    permissions:
+      pull-requests: write
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+        with:
+          persist-credentials: false
+          sparse-checkout: .github
+          sparse-checkout-cone-mode: true
+          fetch-depth: 1
+
+      - name: Comment on large bundle size increases
+        uses: actions/github-script@3a2844b7e9c422d3c10d287c895573f7108da1b3 # v9.0.0
+        with:
+          github-token: ${{ secrets.GITHUB_TOKEN }}
+          script: |
+            const run = require('./.github/scripts/bundle_size_limits_comment');
+            await run({ github, context });