fix: restore E2E coverage source mapping (#14950)

## Summary

E2E coverage has been reported as either missing or 100% since
`build.sourcemap: 'hidden'` landed; this restores the source mapping and
adds guards so a degenerate tracefile fails loudly instead of being
announced as a milestone.

## Changes

- **What**:
- The E2E build sets `COLLECT_COVERAGE=true`, which re-injects the `//#
sourceMappingURL=` comment. Everything that ships to users keeps
`'hidden'`, so the `.js.map` 404 noise FE-1405 removed stays gone.
`GENERATE_SOURCEMAP` can't carry this — `Comfy-Org/cloud` already sets
it true for the staging and prod builds.
- `CI: E2E Coverage` asserts the merged tracefile still has
source-mapped files before stripping bundle paths, with an error that
names the cause.
- `coverage-slack-notify.ts` counts only `src/`/`packages/` files and
treats an implausibly small file set as no data.

## Review Focus

Root cause: monocart-coverage-reports resolves source maps *only* from
the `//# sourceMappingURL=` comment in the served bundle
(`lib/converter/collect-source-maps.js`).
#14209 switched
`build.sourcemap` to `'hidden'`, which emits the `.map` files but strips
that comment, so every V8 coverage entry stayed at its served path
(`localhost-8188/assets/*.js`).

The merge job strips those paths, which left two failure modes:

- Nothing survives → `lcov: ERROR: no valid records found` → job fails →
no `e2e-coverage` artifact → the Slack report silently drops its E2E
line (what you see after
#14809).
- One third-party script survives (`js.stripe.com/dahlia/stripe.js`,
fully covered) → E2E reported as 100% (`e2e-coverage` artifacts drop
from ~350 KB to ~28 KB). That is the source of the "GOAL REACHED: E2E
test coverage hit 100%" messages.

Replaying the current script against the real 28 KB artifact reproduces
the Slack message exactly (`E2E: 68.5% → 100.0% (+31.5%)`); with this
change the same input produces no post.

The only source-mapped E2E artifacts after 2026-07-30 came from PR
branches not yet rebased past #14209 — hence the decay from ~170/day to
zero rather than a clean cutover.

Note the stored `e2e-coverage-baseline` currently holds the bogus 100%,
so the first run after this merges will look like a large regression and
post nothing; the baseline self-heals on that same run.

---------

Co-authored-by: Connor Byrne <c.byrne@comfy.org>

Author: christian-byrne

.github/workflows/ci-tests-e2e-coverage.yaml

@@ -85,6 +85,16 @@ jobs:
             fi
           done
 
+      - name: Assert coverage was mapped back to source
+        if: steps.coverage-shards.outputs.has-coverage == 'true'
+        run: |
+          MAPPED_SF=$(grep -cE '^SF:(src|packages)/' coverage/playwright/coverage.lcov || true)
+          echo "Source-mapped files: $MAPPED_SF" >> "$GITHUB_STEP_SUMMARY"
+          if [ "${MAPPED_SF:-0}" -lt 100 ]; then
+            echo "::error::Only $MAPPED_SF files under src/ or packages/ in the merged tracefile. Observed paths: $(grep -m 5 '^SF:' coverage/playwright/coverage.lcov | tr '\n' ' '). Served bundle paths mean the E2E build dropped its '//# sourceMappingURL=' comment — check it ran with COLLECT_COVERAGE=true (vite.config.mts build.sourcemap)."
+            exit 1
+          fi
+
       - name: Strip non-source entries from coverage
         if: steps.coverage-shards.outputs.has-coverage == 'true'
         run: |

.github/workflows/ci-tests-e2e.yaml

@@ -36,6 +36,8 @@ jobs:
         uses: ./.github/actions/setup-frontend
         with:
           include_build_step: true
+        env:
+          COLLECT_COVERAGE: 'true'
 
       # Upload only built dist/ (containerized test jobs will pnpm install without cache)
       - name: Upload built frontend
@@ -260,7 +262,7 @@ jobs:
 
       - name: Download built frontend
         if: steps.detect.outputs.has-new-tests == 'true'
-        uses: actions/download-artifact@v7
+        uses: actions/download-artifact@v8
         with:
           name: frontend-dist
           path: dist/

scripts/coverage-slack-notify.test.ts

@@ -0,0 +1,61 @@
+import { describe, expect, it } from 'vitest'
+
+import { parseLcovContent } from './coverage-slack-notify'
+
+function lcov(entries: [file: string, lf: number, lh: number][]): string {
+  return entries
+    .map(([file, lf, lh]) => `SF:${file}\nLF:${lf}\nLH:${lh}\nend_of_record`)
+    .join('\n')
+}
+
+function sourceEntries(
+  count: number,
+  lf: number,
+  lh: number
+): [string, number, number][] {
+  return Array.from({ length: count }, (_, i) => [
+    `src/components/Component${i}.vue`,
+    lf,
+    lh
+  ])
+}
+
+describe('parseLcovContent', () => {
+  it('reports the ratio of covered to total lines', () => {
+    const result = parseLcovContent(lcov(sourceEntries(120, 10, 7)))
+
+    expect(result).toEqual({
+      percentage: 70,
+      totalLines: 1200,
+      coveredLines: 840
+    })
+  })
+
+  it('ignores files outside src/ and packages/', () => {
+    const result = parseLcovContent(
+      lcov([
+        ...sourceEntries(120, 10, 5),
+        ['localhost-8188/assets/index-a1b2c3.js', 1000, 1000],
+        ['js.stripe.com/dahlia/stripe.js', 500, 500]
+      ])
+    )
+
+    expect(result?.totalLines).toBe(1200)
+    expect(result?.percentage).toBe(50)
+  })
+
+  // E2E coverage that fails to map back to source leaves only third-party
+  // scripts behind, which are fully covered and would report as 100%.
+  it('returns null when too few project files are present', () => {
+    expect(
+      parseLcovContent(lcov([['js.stripe.com/dahlia/stripe.js', 500, 500]]))
+    ).toBeNull()
+
+    expect(parseLcovContent(lcov(sourceEntries(99, 10, 10)))).toBeNull()
+    expect(parseLcovContent(lcov(sourceEntries(100, 10, 10)))).not.toBeNull()
+  })
+
+  it('returns null for an empty tracefile', () => {
+    expect(parseLcovContent('')).toBeNull()
+  })
+})

scripts/coverage-slack-notify.ts

@@ -5,6 +5,11 @@ const MILESTONE_STEP = 5
 const MIN_DELTA = 0.05
 const BAR_WIDTH = 20
 
+/** Repo-relative prefixes of the files whose coverage this report is about. */
+const PROJECT_SOURCE = /^(src|packages)\//
+/** Below this the tracefile is degenerate, not sparse, and its ratio is noise. */
+const MIN_SOURCE_FILES = 100
+
 interface CoverageData {
   percentage: number
   totalLines: number
@@ -19,13 +24,16 @@ interface SlackBlock {
   }
 }
 
-function parseLcovContent(content: string): CoverageData | null {
+export function parseLcovContent(content: string): CoverageData | null {
   const perFile = new Map<string, { lf: number; lh: number }>()
   let currentFile = ''
 
   for (const line of content.split('\n')) {
     if (line.startsWith('SF:')) {
-      currentFile = line.slice(3)
+      const file = line.slice(3)
+      currentFile = PROJECT_SOURCE.test(file) ? file : ''
+    } else if (!currentFile) {
+      continue
     } else if (line.startsWith('LF:')) {
       const n = parseInt(line.slice(3), 10) || 0
       const entry = perFile.get(currentFile) ?? { lf: 0, lh: 0 }
@@ -46,7 +54,7 @@ function parseLcovContent(content: string): CoverageData | null {
     coveredLines += lh
   }
 
-  if (totalLines === 0) return null
+  if (totalLines === 0 || perFile.size < MIN_SOURCE_FILES) return null
 
   return {
     percentage: (coveredLines / totalLines) * 100,
@@ -230,4 +238,6 @@ function main() {
   process.stdout.write(JSON.stringify(payload))
 }
 
-main()
+if (process.argv[1] && import.meta.url === `file://${process.argv[1]}`) {
+  main()
+}

vite.config.mts

@@ -28,6 +28,7 @@ const ANALYZE_BUNDLE = process.env.ANALYZE_BUNDLE === 'true'
 const VITE_REMOTE_DEV = process.env.VITE_REMOTE_DEV === 'true'
 const DISABLE_TEMPLATES_PROXY = process.env.DISABLE_TEMPLATES_PROXY === 'true'
 const GENERATE_SOURCEMAP = process.env.GENERATE_SOURCEMAP !== 'false'
+const COLLECT_COVERAGE = process.env.COLLECT_COVERAGE === 'true'
 const IS_STORYBOOK = process.env.npm_lifecycle_event === 'storybook'
 
 const CRITICAL_COVERAGE_DIRS = [
@@ -546,7 +547,9 @@ export default defineConfig({
     // browser-facing `//# sourceMappingURL=` comment is NOT injected into the JS
     // bundles. This kills the ~57k/3d `/assets/*.js.map` 404 noise in prod
     // (the .map files aren't served) without losing Sentry symbolication. See FE-1405.
-    sourcemap: GENERATE_SOURCEMAP ? 'hidden' : false,
+    // A coverage build serves its own .map files and needs the comment back:
+    // monocart maps V8 coverage to src/** only by following it.
+    sourcemap: GENERATE_SOURCEMAP && (COLLECT_COVERAGE || 'hidden'),
     // Exclude heavy optional vendor chunks from initial module preload
     // These chunks are only needed when their features are used (3D, terminal, etc.)
     modulePreload: {