fix(coverage): .tmp directory conflicts with --shard option

packages/coverage-istanbul/src/provider.ts

@@ -98,7 +98,10 @@ export class IstanbulCoverageProvider extends BaseCoverageProvider implements Co
       relativePath: !this.options.allowExternal,
     })
 
-    this.coverageFilesDirectory = resolve(this.options.reportsDirectory, '.tmp')
+    const shard = this.ctx.config.shard
+    const tempDirectory = `.tmp${shard ? `-${shard.index}-${shard.count}` : ''}`
+
+    this.coverageFilesDirectory = resolve(this.options.reportsDirectory, tempDirectory)
   }
 
   resolveOptions() {

packages/coverage-v8/src/provider.ts

@@ -101,7 +101,10 @@ export class V8CoverageProvider extends BaseCoverageProvider implements Coverage
       relativePath: !this.options.allowExternal,
     })
 
-    this.coverageFilesDirectory = resolve(this.options.reportsDirectory, '.tmp')
+    const shard = this.ctx.config.shard
+    const tempDirectory = `.tmp${shard ? `-${shard.index}-${shard.count}` : ''}`
+
+    this.coverageFilesDirectory = resolve(this.options.reportsDirectory, tempDirectory)
   }
 
   resolveOptions() {

test/coverage-test/option-tests/shard.test.ts

@@ -0,0 +1,9 @@
+import { readdirSync } from 'node:fs'
+import { expect, test } from 'vitest'
+
+test('temporary directory is postfixed with --shard value', () => {
+  const files = readdirSync('./coverage')
+
+  expect(files).toContain('.tmp-1-4')
+  expect(files).not.toContain('.tmp')
+})

test/coverage-test/testing-options.mjs

@@ -43,6 +43,14 @@ const testCases = [
     },
     assertionConfig: null,
   },
+  {
+    testConfig: {
+      name: 'temp directory with shard',
+      include: ['option-tests/shard.test.ts'],
+      shard: '1/4',
+    },
+    assertionConfig: null,
+  },
 ]
 
 for (const provider of ['v8', 'istanbul']) {