CI: Track SWC native binary size in PR stats comment (#92938)

### What? Adds a new "Native Binary" section to the `Stats from current PR` comment posted by the `generate-pull-request-stats` GitHub Action. The section reports the size of the SWC native binary (`packages/next-swc/native/*.node`) built for the PR and the change relative to the latest value recorded on `canary`. Example row: > | Metric | Canary | PR | Change | Trend | > |:-------|-------:|---:|-------:|:-----:| > | SWC Binary Size | 113 MB | 121 MB | 🔴 +7.34 MB (+6%) | ▁▃▅▇█ | ### Why? The `.node` binary is a sizable, user-facing artifact (it ships with `next`). Today there's no visibility on its size in PRs, so regressions from Rust/Cargo changes are easy to miss. Surfacing the size (and a diff vs. canary) in the existing stats comment gives immediate feedback on any change that affects the binary. ### How? - **Measurement (`.github/actions/next-stats-action/src/run/index.js`):** After the action copies the pre-built native binary into the working dirs, sum the size of every `*.node` file under the action's `native/` directory and store it as `General.swcBinarySize` on both the canary and PR stat sets. - **Canary baseline via KV history (`.github/actions/next-stats-action/src/add-comment.js`):** The workflow downloads a single pre-built binary and copies it into both the canary and PR checkouts, so an in-run diff would always be zero. Instead, for PR runs we override `mainRepoStats.General.swcBinarySize` with the most recent `swcBinarySize` from the Vercel KV history (the same store already used for other canary metrics). Canary runs keep the measured value, and the existing persistence path (`saveToHistory` / `General`) writes it back so future PRs see an updated baseline. If no history exists yet, the Canary column renders `N/A` and no change is shown. - **Rendering:** New `generateNativeBinarySection` emits a `<details>`-wrapped section styled like Bundle Sizes / All Metrics, rendered right after the Bundle Sizes block. It reuses `prettify`, `formatChange`, and `generateTrendBar` so formatting, thresholds, and sparklines are consistent with the rest of the comment. A tight threshold entry (`swcBinarySize: { absoluteMin: 10 KB, percentMin: 0.5%, percentOnly: 0.05% }`) is added so meaningful movement is flagged while tiny determinism noise is ignored. - **Top-line summary:** Because `swcBinarySize` lives on `General`, the existing `generateChangeSummary` automatically promotes significant changes into the headline regression/improvement table at the top of the comment, using the label `SWC Binary Size`. - **Sharded runs:** The workflow runs two sharded jobs (Webpack and Turbopack). The binary is bundler-independent, so both shards report the same value; `aggregate-results.js` merges `General` via `Object.assign`, which is correct here (last-writer-wins on an identical value). No workflow changes are required — the existing `pull_request_stats.yml` already downloads the `next-swc-binary` artifact and copies it into the action's `native/` directory. ### Verification Smoke-tested `add-comment.js` locally with `LOCAL_STATS=1` in two scenarios: - No KV history configured → Canary column renders `N/A`, PR value renders, Change is `-`, section still shown. - Mocked KV history containing prior `swcBinarySize` values → full diff rendered in both the Native Binary section and the top-level significance summary, with a sparkline of the last 5 historical entries. Closes NEXT-  --------- Co-authored-by: Tobias Koppers <[email protected]> Co-authored-by: Claude <[email protected]>
2026-09-24 17:00:51 +00:00 · 2026-04-18 20:58:47 +02:00
parent 87e7b083b8
commit bb2a4457b6
2 changed files with 109 additions and 0 deletions
@@ -55,6 +55,7 @@ const METRIC_LABELS = {
  buildDurationCachedTurbo: 'Turbo Build Time (cached)',
  // General metrics
  nodeModulesSize: 'node_modules Size',
+  swcBinarySize: 'SWC Binary Size',
 }

 // Group configuration for organizing the comment
@@ -209,6 +210,10 @@ const METRIC_THRESHOLDS = {
  // <10KB AND <1%, OR <0.01%
  nodeModulesSize: { absoluteMin: 10240, percentMin: 1, percentOnly: 0.01 },

+  // SWC native binary (~tens of MB): deterministic, but smaller baseline
+  // <10KB AND <0.5%, OR <0.05%
+  swcBinarySize: { absoluteMin: 10240, percentMin: 0.5, percentOnly: 0.05 },
+
  // Bundle sizes (KB-MB): deterministic
  // <2KB AND <1%, OR <0.1%
  bytes: { absoluteMin: 2048, percentMin: 1, percentOnly: 0.1 },
@@ -973,6 +978,57 @@ function generateDiffsSection(result) {
  return content
 }

+// Find the most recent value for a metric in the KV history.
+function getLatestHistoricalValue(history, metricKey) {
+  if (!history?.entries?.length) return undefined
+  for (let i = history.entries.length - 1; i >= 0; i--) {
+    const val = history.entries[i].metrics?.[metricKey]
+    if (typeof val === 'number') return val
+  }
+  return undefined
+}
+
+// Generate the dedicated Native Binary section shown after Bundle Sizes.
+function generateNativeBinarySection(mainStats, diffStats, history) {
+  const mainGeneral = mainStats?.General || {}
+  const diffGeneral = diffStats?.General || {}
+
+  const mainVal = mainGeneral.swcBinarySize
+  const diffVal = diffGeneral.swcBinarySize
+
+  // Nothing to show if we don't have any measurement
+  if (typeof mainVal !== 'number' && typeof diffVal !== 'number') return ''
+
+  const mainStr = prettify(mainVal, 'bytes')
+  const diffStr = prettify(diffVal, 'bytes')
+  const change = formatChange(mainVal, diffVal, 'bytes', 'swcBinarySize')
+  const histValues = getHistoricalValues(history, 'swcBinarySize')
+  const sparkline = generateTrendBar(histValues)
+
+  const hasTrend = Boolean(sparkline)
+  const header = hasTrend
+    ? `| Metric | Canary | PR | Change | Trend |
+|:-------|-------:|---:|-------:|:-----:|`
+    : `| Metric | Canary | PR | Change |
+|:-------|-------:|---:|-------:|`
+
+  const row = hasTrend
+    ? `| SWC Binary Size | ${mainStr} | ${diffStr} | ${change.text} | ${sparkline} |`
+    : `| SWC Binary Size | ${mainStr} | ${diffStr} | ${change.text} |`
+
+  return `<details>
+<summary><strong>🦀 Native Binary</strong></summary>
+
+Size of the native SWC binary (\`packages/next-swc/native/*.node\`). The Canary column is the most recent value recorded on the canary branch.
+
+${header}
+${row}
+
+</details>
+
+`
+}
+
 function generatePrTarballSection(actionInfo) {
  if (actionInfo.isRelease || !actionInfo.githubHeadSha) return ''

@@ -1016,6 +1072,24 @@ module.exports = async function addComment(
    const result = results[i]
    const isLastResult = i === results.length - 1

+    // The native SWC binary is shared between the canary and PR checkouts in
+    // a single run (the workflow downloads it once and copies it into both),
+    // so the in-run "canary" value is identical to the PR value. Override the
+    // canary baseline with the last recorded value from KV history so the
+    // diff is meaningful. Canary runs skip this and keep the measured value.
+    if (!actionInfo.isRelease && result.mainRepoStats?.General) {
+      const historicalSwcSize = getLatestHistoricalValue(
+        history,
+        'swcBinarySize'
+      )
+      if (typeof historicalSwcSize === 'number') {
+        result.mainRepoStats.General.swcBinarySize = historicalSwcSize
+      } else {
+        // No history yet — hide the canary value so the table renders N/A
+        delete result.mainRepoStats.General.swcBinarySize
+      }
+    }
+
    // Add summary showing only significant changes (not collapsed)
    if (i === 0) {
      comment += generateChangeSummary(
@@ -1041,6 +1115,13 @@ module.exports = async function addComment(
      comment += `<details>\n<summary><strong>📦 Bundle Sizes</strong></summary>\n\n${bundleSection}</details>\n\n`
    }

+    // Add native binary size section (not collapsed, small)
+    comment += generateNativeBinarySection(
+      result.mainRepoStats,
+      result.diffRepoStats,
+      history
+    )
+
    // Add diffs (already collapsed)
    comment += generateDiffsSection(result)

@@ -9,6 +9,32 @@ const collectDiffs = require('./collect-diffs')
 const { statsAppDir, diffRepoDir } = require('../constants')
 const { calcStats } = require('../util/stats')

+// Location of the native binary that the workflow copies into the action dir.
+// From src/run/index.js → .github/actions/next-stats-action/native
+const nativeBinaryDir = path.join(__dirname, '../../native')
+
+// Sum the size of all *.node files in the action's native/ directory.
+async function getSwcBinarySize() {
+  try {
+    const entries = await fs.readdir(nativeBinaryDir)
+    let total = 0
+    let found = 0
+    for (const entry of entries) {
+      if (!entry.endsWith('.node')) continue
+      const stat = await fs.stat(path.join(nativeBinaryDir, entry))
+      if (stat.isFile()) {
+        total += stat.size
+        found++
+      }
+    }
+    if (found === 0) return null
+    return total
+  } catch (err) {
+    logger(`Unable to measure SWC binary size: ${err.message}`)
+    return null
+  }
+}
+
 // Number of iterations for build benchmarks to get stable median
 const BUILD_BENCHMARK_ITERATIONS = 5

@@ -57,6 +83,7 @@ async function runConfigs(
      let curStats = {
        General: {
          nodeModulesSize: null,
+          swcBinarySize: null,
        },
      }

@@ -83,6 +110,7 @@ async function runConfigs(
        curStats.General.nodeModulesSize = await getDirSize(
          path.join(statsAppDir, 'node_modules')
        )
+        curStats.General.swcBinarySize = await getSwcBinarySize()
      }

      // Run builds for selected bundler(s) and collect stats separately