fix(vitest): fix <empty line> logs when interleaving `console.log/e…

…rror` (#6644)

packages/vitest/src/runtime/console.ts

@@ -84,7 +84,7 @@ export function createCustomConsole(defaultState?: WorkerGlobalState) {
       sendLog(type, taskId, content, buffer.length)
     }
     const timer = timers.get(taskId)!
-    buffers.set(taskId, [])
+    buffers.delete(taskId)
     if (type === 'stderr') {
       timer.stderrTime = 0
     }

test/reporters/fixtures/console-interleave.test.ts

@@ -0,0 +1,9 @@
+import { test } from 'vitest';
+
+test('repro', async () => {
+  console.log(1);
+  await new Promise((r) => setTimeout(r, 10));
+  console.error(2);
+  await new Promise((r) => setTimeout(r, 10));
+  console.log(3);
+});

test/reporters/tests/console.test.ts

@@ -1,5 +1,6 @@
 import { resolve } from 'pathe'
-import { expect, test } from 'vitest'
+import { type UserConsoleLog, expect, test } from 'vitest'
+import type { Reporter } from 'vitest/reporters'
 import { DefaultReporter } from 'vitest/reporters'
 import { runVitest } from '../../test-utils'
 
@@ -66,3 +67,33 @@ stderr | console.test.ts
 global stderr afterAll`,
   )
 })
+
+test.for(['forks', 'threads'])('interleave (pool = %s)', async (pool) => {
+  const logs: UserConsoleLog[] = []
+  const { stderr } = await runVitest({
+    root: './fixtures',
+    pool,
+    reporters: [
+      {
+        onUserConsoleLog(log) {
+          logs.push(log)
+        },
+      } satisfies Reporter,
+    ],
+  }, [resolve('./fixtures/console-interleave.test.ts')])
+  expect(stderr).toBe('')
+  expect(logs).toMatchObject([
+    {
+      type: 'stdout',
+      content: expect.stringContaining('1'),
+    },
+    {
+      type: 'stderr',
+      content: expect.stringContaining('2'),
+    },
+    {
+      type: 'stdout',
+      content: expect.stringContaining('3'),
+    },
+  ])
+})