From 4da333b294b6ea13029a81bc6736420c808517df Mon Sep 17 00:00:00 2001
From: Vladimir Sheremet <sleuths.slews0s@icloud.com>
Date: Thu, 3 Oct 2024 13:32:28 +0200
Subject: [PATCH] fix(vitest): don't hang with maxConcurrency 0

---
 packages/vitest/src/node/config/resolveConfig.ts | 7 +++++++
 test/config/test/failures.test.ts                | 7 +++++++
 test/config/vitest.config.ts                     | 1 +
 3 files changed, 15 insertions(+)

diff --git a/packages/vitest/src/node/config/resolveConfig.ts b/packages/vitest/src/node/config/resolveConfig.ts
index fba6f40e1c6b..51babc9840be 100644
--- a/packages/vitest/src/node/config/resolveConfig.ts
+++ b/packages/vitest/src/node/config/resolveConfig.ts
@@ -207,6 +207,13 @@ export function resolveConfig(
     resolved.minWorkers = 1
   }
 
+  if (resolved.maxConcurrency === 0) {
+    logger.console.warn(
+      c.yellow(`The option "maxConcurrency" cannot be set to 0. Using default value ${configDefaults.maxConcurrency} instead.`),
+    )
+    resolved.maxConcurrency = configDefaults.maxConcurrency
+  }
+
   if (resolved.inspect || resolved.inspectBrk) {
     const isSingleThread
       = resolved.pool === 'threads'
diff --git a/test/config/test/failures.test.ts b/test/config/test/failures.test.ts
index 22a08200dbb1..b9a39d5f587f 100644
--- a/test/config/test/failures.test.ts
+++ b/test/config/test/failures.test.ts
@@ -279,3 +279,10 @@ test('mergeReports doesn\'t work with watch mode enabled', async () => {
 
   expect(stderr).toMatch('Cannot merge reports with --watch enabled')
 })
+
+test('maxConcurrency 0 prints a warning', async () => {
+  const { stderr, ctx } = await runVitest({ maxConcurrency: 0 })
+
+  expect(ctx?.config.maxConcurrency).toBe(5)
+  expect(stderr).toMatch('The option "maxConcurrency" cannot be set to 0. Using default value 5 instead.')
+})
diff --git a/test/config/vitest.config.ts b/test/config/vitest.config.ts
index d15b5ad03bb9..19ce7e1ff204 100644
--- a/test/config/vitest.config.ts
+++ b/test/config/vitest.config.ts
@@ -19,6 +19,7 @@ export default defineConfig({
       truncateThreshold: 999,
     },
     coverage: {
+      // test that empty reporter does not throw
       reporter: [],
     },
   },