fix(coverage): workspaces c8 source maps

packages/coverage-c8/src/provider.ts

@@ -100,8 +100,12 @@ export class C8CoverageProvider extends BaseCoverageProvider implements Coverage
     const sourceMapMeta: Record<SourceMapMeta['url'], MapAndSource> = {}
     const extensions = Array.isArray(this.options.extension) ? this.options.extension : [this.options.extension]
 
+    const fetchCache = this.ctx.projects.map(project =>
+      Array.from(project.vitenode.fetchCache.entries()),
+    ).flat()
+
     const entries = Array
-      .from(this.ctx.vitenode.fetchCache.entries())
+      .from(fetchCache)
       .filter(entry => report._shouldInstrument(entry[0]))
       .map(([file, { result }]) => {
         if (!result.map)

test/workspaces/coverage-report-tests/check-coverage.test.ts

@@ -0,0 +1,22 @@
+import { existsSync, readFileSync } from 'node:fs'
+import { normalize } from 'node:path'
+import { expect, test } from 'vitest'
+import libCoverage from 'istanbul-lib-coverage'
+import { resolve } from 'pathe'
+
+test('coverage exists', () => {
+  expect(existsSync('./coverage')).toBe(true)
+  expect(existsSync('./coverage/index.html')).toBe(true)
+})
+
+test('file coverage summary matches', () => {
+  const coverageJson = JSON.parse(readFileSync('./coverage/coverage-final.json', 'utf-8'))
+  const coverageMap = libCoverage.createCoverageMap(coverageJson)
+  const fileCoverage = coverageMap.fileCoverageFor(normalize(resolve('./src/math.ts')))
+
+  // There should be 1 uncovered branch and 1 uncovered function. See math.ts.
+  const { branches, functions } = fileCoverage.toSummary()
+
+  expect(branches.total - branches.covered).toBe(1)
+  expect(functions.total - functions.covered).toBe(1)
+})

test/workspaces/coverage-report-tests/vitest.config.ts

@@ -0,0 +1,7 @@
+import { defineConfig } from 'vitest/config'
+
+export default defineConfig({
+  test: {
+    include: ['./check-coverage.test.ts'],
+  },
+})

test/workspaces/package.json

@@ -3,10 +3,13 @@
   "type": "module",
   "private": true,
   "scripts": {
-    "test": "vitest",
-    "coverage": "vitest run --coverage"
+    "test": "pnpm test:workspace && pnpm test:coverage",
+    "test:workspace": "vitest run",
+    "test:coverage": "vitest run --root coverage-report-tests"
   },
   "devDependencies": {
+    "@types/istanbul-lib-coverage": "^2.0.4",
+    "istanbul-lib-coverage": "^3.2.0",
     "jsdom": "latest",
     "vitest": "workspace:*"
   }

test/workspaces/src/math.ts

@@ -1,3 +1,14 @@
+/* eslint-disable unused-imports/no-unused-vars */
 export function sum(a: number, b: number) {
+  if (a === 3 && b === 4) {
+    // This should be uncovered
+    return 7
+  }
+
   return a + b
 }
+
+function uncoveredFunction() {
+  // This should be uncovered
+  return 1
+}

test/workspaces/vitest.config.ts

@@ -9,6 +9,7 @@ if (process.env.TEST_WATCH) {
 export default defineConfig({
   test: {
     coverage: {
+      enabled: true,
       all: true,
     },
     reporters: ['default', 'json'],