coverage.reporter with a single value causes error while running tests without coverage (v2.0.x)

[ildede]

Describe the bug

The documentation of coverage.reporter on both V2 and V1 say that we can use string as a valid value.

So a minimal vitest.config like this, should work

export default defineConfig({
  test: {
    coverage: {
      reporter: 'json',
    },
  },
})

This works fine with 1.6, but not in 2.0.x.

Error printed while executing pnpm run test. The error is not present while running pnpm run test --coverage

Reproduction

A minimal reproduction case in this repository ildede/vitest-single-reporter-error

System Info

System:
    OS: macOS 14.5
    CPU: (8) arm64 Apple M1 Pro
    Memory: 116.05 MB / 32.00 GB
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 20.9.0 - ~/Library/pnpm/node
    npm: 10.1.0 - ~/Library/pnpm/npm
    pnpm: 9.5.0 - ~/Library/pnpm/pnpm
  Browsers:
    Chrome: 127.0.6533.88
    Safari: 17.5
  npmPackages:
    vitest: ^2.0.5 => 2.0.5

Used Package Manager

pnpm

Validations

• Follow our Code of Conduct
• Read the Contributing Guidelines.
• Read the docs.
• Check that there isn't already an issue that reports the same bug to avoid creating a duplicate.
• Check that this is a concrete bug. For Q&A open a GitHub Discussion or join our Discord Chat Server.
• The provided reproduction is a minimal reproducible example of the bug.

[AriPerkkio]

We have test case for all reporter option types but all those run with coverage: { enabled: true }. This error case seems to come up only when coverage is disabled.

vitest/test/coverage-test/test/reporters.test.ts

Lines 7 to 18 in a7be50d

	test('reporter as string', async () => {
	await runVitest({
	include,
	coverage: {
	reporter: 'json',
	all: false,
	},
	})
	const files = readdirSync('./coverage')
	expect(files).toContain('coverage-final.json')
	})

This might have been caused by refactoring done during #6205.

[osmestad]

If anyone is wondering how to work around this (like me) until 2.1.x gets released, wrapping the reporter string in an array should do the trick. So from:

coverage: { 
       reporter: 'json', 
}

to:

coverage: { 
       reporter: ['json'], 
}