maxCurrency of zero hangs vitest

[dcramer]

Describe the bug

set maxConcurrency to 0 in vitest's config and it seems to not spin up any workers

This appears to be behavior that was introduced somewhere around vitest 1.5.0. IMO it should either error, or "disable" concurrency (e.g. set it to 1).

Reproduction

import tsconfigPaths from "vite-tsconfig-paths";
import { defineConfig } from "vitest/config";

export default defineConfig({
  plugins: [tsconfigPaths()],
  server: {
    watch: {
      ignored: [
        "**/node_modules/**",
        "**/dist/**",
        "**/postgres-data/**",
      ],
    },
  },
  test: {
    coverage: {
      provider: "v8",
      reporter: ["json"],
    },
    maxConcurrency: 0,
    pool: "forks",
    poolOptions: {
      forks: {
        singleFork: true,
      },
      threads: {
        singleThread: true,
      },
    },
    fileParallelism: false,
    globals: true,
    setupFiles: ["./src/test/setup-test-env.ts"],
    include: ["./src/**/*.{test,spec}.{js,mjs,cjs,ts,mts,cts,jsx,tsx}"],
    restoreMocks: true,
  },
});

System Info

System:
    OS: Linux 5.15 Ubuntu 22.04.1 LTS 22.04.1 LTS (Jammy Jellyfish)
    CPU: (24) x64 12th Gen Intel(R) Core(TM) i9-12900KF
    Memory: 27.98 GB / 31.27 GB
    Container: Yes
    Shell: 5.8.1 - /usr/bin/zsh
  Binaries:
    Node: 20.12.1 - ~/.volta/tools/image/node/20.12.1/bin/node
    Yarn: 3.3.0 - ~/.volta/tools/image/yarn/3.3.0/bin/yarn
    npm: 10.5.0 - ~/.volta/tools/image/node/20.12.1/bin/npm
    pnpm: 9.7.0 - ~/.local/share/pnpm/pnp

Used Package Manager

pnpm

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