refactor: correctly override isolate flag

packages/vitest/src/defaults.ts

@@ -62,6 +62,7 @@ export const fakeTimersDefaults = {
 
 const config = {
   allowOnly: !isCI,
+  isolate: true,
   watch: !isCI,
   globals: false,
   environment: 'node' as const,

packages/vitest/src/node/config.ts

@@ -123,15 +123,6 @@ export function resolveConfig(
     }
   }
 
-  if (resolved.isolate) {
-    resolved.poolOptions ??= {}
-    resolved.poolOptions.threads ??= {}
-    // prefer CLI arguments
-    resolved.poolOptions.threads.isolate = options.poolOptions?.threads?.isolate ?? options.isolate ?? resolved.poolOptions.threads.isolate ?? resolved.isolate
-    resolved.poolOptions.forks ??= {}
-    resolved.poolOptions.forks.isolate ??= options.poolOptions?.forks?.isolate ?? options.isolate ?? resolved.poolOptions.forks.isolate ?? resolved.isolate
-  }
-
   // @ts-expect-error -- check for removed API option
   if (resolved.coverage.provider === 'c8')
     throw new Error('"coverage.provider: c8" is not supported anymore. Use "coverage.provider: v8" instead')

packages/vitest/src/node/plugins/index.ts

@@ -51,6 +51,13 @@ export async function VitestPlugin(options: UserConfig = {}, ctx = new Vitest('t
         )
         testConfig.api = resolveApiServerConfig(testConfig)
 
+        testConfig.poolOptions ??= {}
+        testConfig.poolOptions.threads ??= {}
+        testConfig.poolOptions.forks ??= {}
+        // prefer --poolOptions.{name}.isolate CLI arguments over --isolate, but still respect config value
+        testConfig.poolOptions.threads.isolate = options.poolOptions?.threads?.isolate ?? options.isolate ?? testConfig.poolOptions.threads.isolate ?? viteConfig.test?.isolate
+        testConfig.poolOptions.forks.isolate = options.poolOptions?.forks?.isolate ?? options.isolate ?? testConfig.poolOptions.forks.isolate ?? viteConfig.test?.isolate
+
         // store defines for globalThis to make them
         // reassignable when running in worker in src/runtime/setup.ts
         const defines: Record<string, any> = deleteDefineConfig(viteConfig)
@@ -91,6 +98,9 @@ export async function VitestPlugin(options: UserConfig = {}, ctx = new Vitest('t
               allow: resolveFsAllow(getRoot(), testConfig.config),
             },
           },
+          test: {
+            poolOptions: testConfig.poolOptions,
+          },
         }
 
         // chokidar fsevents is unstable on macos when emitting "ready" event

test/config/test/resolution.test.ts

@@ -0,0 +1,104 @@
+import type { UserConfig } from 'vitest'
+import { describe, expect, it } from 'vitest'
+import { createVitest } from 'vitest/node'
+
+async function config(cliOptions: UserConfig, configValue: UserConfig = {}) {
+  const vitest = await createVitest('test', { ...cliOptions, watch: false }, { test: configValue })
+  return vitest.config
+}
+
+describe('correctly defines isolated flags', async () => {
+  it('prefers CLI poolOptions flags over config', async () => {
+    const c = await config({
+      isolate: true,
+      poolOptions: {
+        threads: {
+          isolate: false,
+        },
+        forks: {
+          isolate: false,
+        },
+      },
+    })
+    expect(c.poolOptions?.threads?.isolate).toBe(false)
+    expect(c.poolOptions?.forks?.isolate).toBe(false)
+    expect(c.isolate).toBe(true)
+  })
+
+  it('override CLI poolOptions flags over isolate', async () => {
+    const c = await config({
+      isolate: false,
+      poolOptions: {
+        threads: {
+          isolate: true,
+        },
+        forks: {
+          isolate: true,
+        },
+      },
+    }, {
+      poolOptions: {
+        threads: {
+          isolate: false,
+        },
+        forks: {
+          isolate: false,
+        },
+      },
+    })
+    expect(c.poolOptions?.threads?.isolate).toBe(true)
+    expect(c.poolOptions?.forks?.isolate).toBe(true)
+    expect(c.isolate).toBe(false)
+  })
+
+  it('override CLI isolate flag if poolOptions is not set via CLI', async () => {
+    const c = await config({
+      isolate: true,
+    }, {
+      poolOptions: {
+        threads: {
+          isolate: false,
+        },
+        forks: {
+          isolate: false,
+        },
+      },
+    })
+    expect(c.poolOptions?.threads?.isolate).toBe(true)
+    expect(c.poolOptions?.forks?.isolate).toBe(true)
+    expect(c.isolate).toBe(true)
+  })
+
+  it('keeps user configured poolOptions if no CLI flag is provided', async () => {
+    const c = await config({}, {
+      poolOptions: {
+        threads: {
+          isolate: false,
+        },
+        forks: {
+          isolate: false,
+        },
+      },
+    })
+    expect(c.poolOptions?.threads?.isolate).toBe(false)
+    expect(c.poolOptions?.forks?.isolate).toBe(false)
+    expect(c.isolate).toBe(true)
+  })
+
+  it('isolate config value overrides poolOptions defaults', async () => {
+    const c = await config({}, {
+      isolate: false,
+    })
+    expect(c.poolOptions?.threads?.isolate).toBe(false)
+    expect(c.poolOptions?.forks?.isolate).toBe(false)
+    expect(c.isolate).toBe(false)
+  })
+
+  it('if no isolation is defined in the config, fallback ot undefined', async () => {
+    const c = await config({}, {})
+    expect(c.poolOptions?.threads?.isolate).toBe(undefined)
+    expect(c.poolOptions?.forks?.isolate).toBe(undefined)
+    // set in configDefaults, so it's always defined
+    expect(c.isolate).toBe(true)
+  })
+})