Add post-PR metrics script for GitHub actions

.github/scripts/optimized post-pr-metrics.test.js

@@ -0,0 +1,108 @@
+const fs = require("fs")
+const path = require("path")
+
+const BASELINE_FILE = path.join(".metrics-baseline", "metrics.json")
+const COMMENT_TAG = "<!-- pr-metrics -->"
+
+// ---------- helpers ----------
+
+function readNumber(value) {
+  const n = Number(value)
+  return Number.isFinite(n) && n >= 0 ? n : null
+}
+
+function readCoverage(value) {
+  const n = Number(value)
+  return Number.isFinite(n) && n >= 0 && n <= 100 ? n : null
+}
+
+function safeReadBaseline() {
+  try {
+    if (!fs.existsSync(BASELINE_FILE)) return null
+    const raw = fs.readFileSync(BASELINE_FILE, "utf8")
+    return JSON.parse(raw)
+  } catch {
+    return null // corrupted file safe fallback
+  }
+}
+
+function formatBytes(bytes) {
+  if (bytes == null) return "—"
+  return `${(bytes / 1024).toFixed(1)} KB`
+}
+
+function diffText(current, baseline, formatter = v => v) {
+  if (current == null) return "—"
+  if (!baseline) return formatter(current)
+
+  const diff = current - baseline
+  if (diff === 0) return `${formatter(current)} (no change)`
+
+  const sign = diff > 0 ? "▲" : "▼"
+  return `${formatter(current)} (${sign} ${formatter(Math.abs(diff))})`
+}
+
+function buildComment({ bundle, baselineBundle, coverage, baselineCoverage }) {
+  const bundleRow = diffText(bundle, baselineBundle, formatBytes)
+  const coverageRow = diffText(coverage, baselineCoverage, v => `${v.toFixed(1)}%`)
+
+  return `${COMMENT_TAG}
+## 📊 PR Metrics
+
+| Metric | Value |
+|---|---|
+| Bundle size (gzip) | ${bundleRow} |
+| Test coverage | ${coverageRow} |
+`
+}
+
+// ---------- main function ----------
+
+async function postPrMetrics({ github, context }) {
+  // Skip conditions
+  if (process.env.BUILD_OUTCOME !== "success") return
+  if (process.env.PREVIEW_READY !== "true" && process.env.PREVIEW_READY !== "false") return
+
+  const bundle = readNumber(process.env.BUNDLE_GZIP)
+  const coverage = readCoverage(process.env.COVERAGE)
+
+  const baseline = safeReadBaseline()
+  const baselineBundle = baseline?.bundleSize ?? null
+  const baselineCoverage = readCoverage(baseline?.coverage)
+
+  const body = buildComment({
+    bundle,
+    baselineBundle,
+    coverage,
+    baselineCoverage,
+  })
+
+  const { owner, repo } = context.repo
+  const issue_number = context.issue.number
+
+  const comments = await github.rest.issues.listComments({
+    owner,
+    repo,
+    issue_number,
+  })
+
+  const existing = comments.data.find(c => c.body?.includes(COMMENT_TAG))
+
+  if (existing) {
+    await github.rest.issues.updateComment({
+      owner,
+      repo,
+      comment_id: existing.id,
+      body,
+    })
+  } else {
+    await github.rest.issues.createComment({
+      owner,
+      repo,
+      issue_number,
+      body,
+    })
+  }
+}
+
+module.exports = { postPrMetrics }