fix(coverage-istanbul): clear coverage map after use (#2466)

* test: add coverage snapshots

* fix(coverage-istanbul): clear coverage map after use

- Fixes issues where statement counts were duplicated

Author: AriPerkkio

packages/coverage-istanbul/src/index.ts

@@ -7,5 +7,11 @@ export async function getProvider() {
 
 export function takeCoverage() {
   // @ts-expect-error -- untyped global
-  return globalThis[COVERAGE_STORE_KEY]
+  const coverage = globalThis[COVERAGE_STORE_KEY]
+
+  // Reset coverage map to prevent duplicate results if this is called twice in row
+  // @ts-expect-error -- untyped global
+  globalThis[COVERAGE_STORE_KEY] = {}
+
+  return coverage
 }

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

@@ -2,6 +2,16 @@ import fs from 'fs'
 import { normalize, resolve } from 'pathe'
 import { expect, test } from 'vitest'
 
+interface CoverageFinalJson {
+  default: {
+    [filename: string]: {
+      path: string
+      b: Record<string, number[]>
+      // ... and more unrelated keys
+    }
+  }
+}
+
 test('istanbul html report', async () => {
   const coveragePath = resolve('./coverage/src')
   const files = fs.readdirSync(coveragePath)
@@ -23,6 +33,20 @@ test('istanbul lcov report', async () => {
   expect(lcovReportFiles).toContain('index.html')
 })
 
+test('istanbul json report', async () => {
+  // @ts-expect-error -- generated file
+  const { default: jsonReport } = await import('./coverage/coverage-final.json') as CoverageFinalJson
+
+  const normalizedReport: CoverageFinalJson['default'] = {}
+
+  for (const [filename, coverage] of Object.entries(jsonReport)) {
+    coverage.path = normalizeFilename(coverage.path)
+    normalizedReport[normalizeFilename(filename)] = coverage
+  }
+
+  expect(normalizedReport).toMatchSnapshot()
+})
+
 test('all includes untested files', () => {
   const coveragePath = resolve('./coverage/src')
   const files = fs.readdirSync(coveragePath)
@@ -42,7 +66,7 @@ test('files should not contain query parameters', () => {
 
 test('implicit else is included in branch count', async () => {
   // @ts-expect-error -- generated file
-  const { default: coverageMap } = await import('./coverage/coverage-final.json')
+  const { default: coverageMap } = await import('./coverage/coverage-final.json') as CoverageFinalJson
 
   const filename = normalize(resolve('./src/implicitElse.ts'))
   const fileCoverage = coverageMap[filename]
@@ -57,3 +81,7 @@ test('file using import.meta.env is included in report', async () => {
 
   expect(files).toContain('importEnv.ts.html')
 })
+
+function normalizeFilename(filename: string) {
+  return filename.replace(normalize(process.cwd()), '<root>')
+}