From 8a18c8e20a19f2c8d9f402e426886999f378c389 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ari=20Perkki=C3=B6?= <ari.perkkio@gmail.com>
Date: Tue, 17 Jun 2025 19:41:37 +0300
Subject: [PATCH] fix(cli): throw error when `--shard x/<count>` exceeds count
 of test files (#8112)

---
 packages/vitest/src/node/pool.ts      |  7 +++++++
 test/config/test/failures.test.ts     | 12 ++++++++++++
 test/coverage-test/test/shard.test.ts |  8 ++++----
 3 files changed, 23 insertions(+), 4 deletions(-)

diff --git a/packages/vitest/src/node/pool.ts b/packages/vitest/src/node/pool.ts
index 7244b99a2..405610307 100644
--- a/packages/vitest/src/node/pool.ts
+++ b/packages/vitest/src/node/pool.ts
@@ -224,6 +224,13 @@ export function createPool(ctx: Vitest): ProcessPool {
 
     async function sortSpecs(specs: TestSpecification[]) {
       if (ctx.config.shard) {
+        if (!ctx.config.passWithNoTests && ctx.config.shard.count > specs.length) {
+          throw new Error(
+            '--shard <count> must be a smaller than count of test files. '
+            + `Resolved ${specs.length} test files for --shard=${ctx.config.shard.index}/${ctx.config.shard.count}.`,
+          )
+        }
+
         specs = await sequencer.shard(specs)
       }
       return sequencer.sort(specs)
diff --git a/test/config/test/failures.test.ts b/test/config/test/failures.test.ts
index e14656edb..0b37e0216 100644
--- a/test/config/test/failures.test.ts
+++ b/test/config/test/failures.test.ts
@@ -51,6 +51,18 @@ test('shard index must be smaller than count', async () => {
   expect(stderr).toMatch('Error: --shard <index> must be a positive number less then <count>')
 })
 
+test('shard count must be smaller than count of test files', async () => {
+  const { stderr } = await runVitest({ root: './fixtures/shard', shard: '1/4', include: ['**/*.test.js'] })
+
+  expect(stderr).toMatch('Error: --shard <count> must be a smaller than count of test files. Resolved 3 test files for --shard=1/4.')
+})
+
+test('shard count can be smaller than count of test files when passWithNoTests', async () => {
+  const { stderr } = await runVitest({ root: './fixtures/shard', shard: '1/4', passWithNoTests: true, include: ['**/*.test.js'] })
+
+  expect(stderr).toMatch('')
+})
+
 test('inspect requires changing pool and singleThread/singleFork', async () => {
   const { stderr } = await runVitest({ inspect: true })
 
diff --git a/test/coverage-test/test/shard.test.ts b/test/coverage-test/test/shard.test.ts
index 523e57ef0..cb7cba717 100644
--- a/test/coverage-test/test/shard.test.ts
+++ b/test/coverage-test/test/shard.test.ts
@@ -2,16 +2,16 @@ import { readdirSync } from 'node:fs'
 import { expect } from 'vitest'
 import { coverageTest, normalizeURL, runVitest, test } from '../utils'
 
-test('{ shard: 1/4 }', async () => {
+test('{ shard: 1/3 }', async () => {
   await runVitest({
-    include: [normalizeURL(import.meta.url)],
-    shard: '1/4',
+    include: [normalizeURL(import.meta.url), 'fixtures/test/math.test.ts', 'fixtures/test/even.test.ts'],
+    shard: '1/3',
   })
 })
 
 coverageTest('temporary directory is postfixed with --shard value', () => {
   const files = readdirSync('./coverage')
 
-  expect(files).toContain('.tmp-1-4')
+  expect(files).toContain('.tmp-1-3')
   expect(files).not.toContain('.tmp')
 })
-- 
2.51.2