Can you reason about this change? Why shouldn't default values match with the shape of resolved ones?

Since coverageConfigDefaults is available externally, I was under the impression that it should represent the raw/default config values and not the fully normalized/resolved runtime config values. If this is the wrong impression let me know.

External usage

import { coverageConfigDefaults } from 'vitest/config';
// OR
import { coverageConfigDefaults } from "vite-plus";

We have to typecast it to as CoverageOptions on line 119 in configDefaults. This skips some typescript checks.

coverage: coverageConfigDefaults as CoverageV8Options, // line 119
                    ^--- ResolvedCoverageOptions

In the docs the default value for coverage.reporter doesn't match with the actual value. The expected value is not possible with ResolvedCoverageOptions since it's more restrictive.

   // expeted value according to the docs
   reporter: [
    'text',
    'html',
    'clover',
    'json',
  ],
  // actual value 
  reporter: [
    ['text', {}],
    ['html', {}],
    ['clover', {}],
    ['json', {}],
  ],

coverageConfigDefaults now aligns with the code style of benchmarkConfigDefaults above it.

export const benchmarkConfigDefaults: Required<
  Omit<BenchmarkUserOptions, 'outputFile' | 'compare' | 'outputJson'>
>

Yeah that makes sense. Also by not exposing the resolved types it allows us to use something completely different type internally in future, if ever needed.

I think we should use here FieldsWithDefaultValues so that we don't create two separate source of truth that can be out-of-sync:

We should also define default values for following properties here:

include
ignoreClassMethods
changed
skipFull
thresholds
watermarks

Ok just tried updating the type with FieldsWithDefaultValues and adding the suggested properties.

/** Fields that have default values. Internally these will always be defined. */
export type FieldsWithDefaultValues // added export
  = | 'provider'
    | 'enabled'
    | 'clean'
    | 'cleanOnRerun'
    | 'reportsDirectory'
    | 'exclude'
    | 'reportOnFailure'
    | 'allowExternal'
    | 'processingConcurrency'
// added fields below
    | 'reporter' // required for no ts errors in packages/vitest/src/node/coverage.ts
    | 'excludeAfterRemap' // required for no ts errors in packages/vitest/src/node/coverage.ts
    | 'include'
    | 'ignoreClassMethods'
    | 'changed'
    | 'skipFull'
    // | 'thresholds' // default value is undefined?
    | 'watermarks'

and

// These are the generic defaults for coverage. Providers may also set some provider specific defaults.
export const coverageConfigDefaults: Required<Pick<CoverageOptions, FieldsWithDefaultValues>> = {
  provider: 'v8',
  enabled: false,
  clean: true,
  cleanOnRerun: true,
  reportsDirectory: './coverage',
  exclude: [],
  reportOnFailure: false,
  reporter: [
    'text',
    'html',
    'clover',
    'json',
  ],
  allowExternal: false,
  excludeAfterRemap: false,
  processingConcurrency: Math.min(
    20,
    os.availableParallelism?.() ?? os.cpus().length,
  ),
  include: [], // Default: Files that were imported during test run
  ignoreClassMethods: [],
  changed: false,
  skipFull: false,
  // thresholds: undefined,
  watermarks: {
    statements: [50, 80],
    functions: [50, 80],
    branches: [50, 80],
    lines: [50, 80],
  },
}

The issues / changes:

• adding export to FieldsWithDefaultValues
• 'reporter' and 'excludeAfterRemap' need to be also defined otherwise we get tsc errors in packages/vitest/src/node/coverage.ts
• include has as default 'Files that were imported during test run' is setting include: [] correct in coverageConfigDefaults?
• thresholds seems to have undefined as default? So it should not be part of FieldsWithDefaultValues?

Not sure about include and thresholds fields

'reporter' and 'excludeAfterRemap' need to be also defined otherwise we get tsc errors in packages/vitest/src/node/coverage.ts

Sounds correct.

Looks like incude and thresholds should actually not have default values. So let's leave them out of FieldsWithDefaultValues. These checks should not pass when user does not define values there:

Otherwise looks good.

Yes leaving out include and thresholds is also what I was thinking.

We also have to leave out changed since its default value is actually undefined and not false (Inherits the default value from test.changed). I've also fixed the changed comment and removed the @default: false.

Think this PR is good to go!