fix(coverage): v8 to prevent crash on dynamic CJS files (#3657)

Author: AriPerkkio

packages/coverage-v8/src/provider.ts

@@ -110,7 +110,7 @@ export class V8CoverageProvider extends BaseCoverageProvider implements Coverage
     }
 
     const converted = await Promise.all(scriptCoverages.map(async ({ url, functions }) => {
-      const sources = await this.getSources(url)
+      const sources = await this.getSources(url, functions)
 
       // If no source map was found from vite-node we can assume this file was not run in the wrapper
       const wrapperLength = sources.sourceMap ? WRAPPER_LENGTH : 0
@@ -204,7 +204,7 @@ export class V8CoverageProvider extends BaseCoverageProvider implements Coverage
     }))
   }
 
-  private async getSources(url: string): Promise<{
+  private async getSources(url: string, functions: Profiler.FunctionCoverage[] = []): Promise<{
     source: string
     originalSource?: string
     sourceMap?: { sourcemap: EncodedSourceMap }
@@ -217,7 +217,12 @@ export class V8CoverageProvider extends BaseCoverageProvider implements Coverage
 
     const map = transformResult?.map
     const code = transformResult?.code
-    const sourcesContent = map?.sourcesContent?.[0] || await fs.readFile(filePath, 'utf-8')
+    const sourcesContent = map?.sourcesContent?.[0] || await fs.readFile(filePath, 'utf-8').catch(() => {
+      // If file does not exist construct a dummy source for it.
+      // These can be files that were generated dynamically during the test run and were removed after it.
+      const length = findLongestFunctionLength(functions)
+      return '.'.repeat(length)
+    })
 
     // These can be uncovered files included by "all: true" or files that are loaded outside vite-node
     if (!map)
@@ -261,3 +266,14 @@ function removeViteHelpersFromSourceMaps(source: string | undefined, map: Encode
 
   return combinedMap as EncodedSourceMap
 }
+
+/**
+ * Find the function with highest `endOffset` to determine the length of the file
+ */
+function findLongestFunctionLength(functions: Profiler.FunctionCoverage[]) {
+  return functions.reduce((previous, current) => {
+    const maxEndOffset = current.ranges.reduce((endOffset, range) => Math.max(endOffset, range.endOffset), 0)
+
+    return Math.max(previous, maxEndOffset)
+  }, 0)
+}

test/coverage-test/.gitignore

@@ -0,0 +1 @@
+src/dynamic-file.ignore.*

test/coverage-test/coverage-report-tests/__snapshots__/c8.report.test.ts.snap

@@ -16,6 +16,8 @@ exports[`custom json report 1`] = `
     "<process-cwd>/src/Defined.vue",
     "<process-cwd>/src/Hello.vue",
     "<process-cwd>/src/another-setup.ts",
+    "<process-cwd>/src/dynamic-file-esm.ignore.mjs",
+    "<process-cwd>/src/dynamic-files.ts",
     "<process-cwd>/src/function-count.ts",
     "<process-cwd>/src/implicitElse.ts",
     "<process-cwd>/src/importEnv.ts",

test/coverage-test/coverage-report-tests/__snapshots__/custom.report.test.ts.snap

@@ -0,0 +1,47 @@
+import { existsSync, rmSync, writeFileSync } from 'node:fs'
+import { createRequire } from 'node:module'
+import { fileURLToPath } from 'node:url'
+
+export async function runDynamicFileESM() {
+  const filename = fileURLToPath(new URL('./dynamic-file-esm.ignore.mjs', import.meta.url))
+
+  if (existsSync(filename))
+    rmSync(filename)
+
+  writeFileSync(filename, `
+// File created by coverage-test/src/dynamic-files.ts
+export function run() {
+  return "Import works"
+}
+function uncovered() {}
+  `.trim(), 'utf-8')
+
+  const { run } = await import(filename)
+
+  if (run() !== 'Import works')
+    throw new Error(`Failed to run ${filename}`)
+
+  rmSync(filename)
+}
+
+export async function runDynamicFileCJS() {
+  const filename = fileURLToPath(new URL('./dynamic-file-cjs.ignore.js', import.meta.url))
+
+  if (existsSync(filename))
+    rmSync(filename)
+
+  writeFileSync(filename, `
+// File created by coverage-test/src/dynamic-files.ts
+module.exports.run = function run() {
+  return "Import works"
+}
+function uncovered() {}
+  `.trim(), 'utf-8')
+
+  const { run } = createRequire(import.meta.url)(filename)
+
+  if (run() !== 'Import works')
+    throw new Error(`Failed to run ${filename}`)
+
+  rmSync(filename)
+}

test/coverage-test/coverage-report-tests/__snapshots__/istanbul.report.test.ts.snap

@@ -2,6 +2,11 @@ import { expect, test } from 'vitest'
 import { implicitElse } from '../src/implicitElse'
 import { useImportEnv } from '../src/importEnv'
 import { second } from '../src/function-count'
+import { runDynamicFileCJS, runDynamicFileESM } from '../src/dynamic-files'
+
+// Browser mode crashes with dynamic files. Enable this when browser mode works.
+// To keep istanbul report consistent between browser and node, skip dynamic tests when istanbul is used.
+const skipDynamicFiles = process.env.COVERAGE_PROVIDER === 'istanbul' || !process.env.COVERAGE_PROVIDER
 
 const { pythagoras } = await (() => {
   if ('__vitest_browser__' in globalThis)
@@ -27,3 +32,11 @@ test('import meta env', () => {
 test('cover function counts', () => {
   expect(second()).toBe(2)
 })
+
+test.skipIf(skipDynamicFiles)('run dynamic ESM file', async () => {
+  await runDynamicFileESM()
+})
+
+test.skipIf(skipDynamicFiles)('run dynamic CJS file', async () => {
+  await runDynamicFileCJS()
+})

test/coverage-test/coverage-report-tests/__snapshots__/v8.report.test.ts.snap

@@ -5,6 +5,7 @@ const UPDATE_SNAPSHOTS = false
 
 const provider = process.argv[1 + process.argv.indexOf('--provider')]
 const isBrowser = process.argv.includes('--browser')
+process.env.COVERAGE_PROVIDER = provider
 
 const threadsConfig = [{ threads: true }, { threads: false }, { singleThread: true }]