vitest-dev/vitest · error · Error

pretty-format: Option "theme" has a key

Error message

pretty-format: Option "theme" has a key "${key}" whose value "${value}" is undefined in ansi-styles.

What it means

When highlight is enabled, getColorsHighlight maps each DEFAULT_THEME key to an ansi-styles color. If the configured theme value (e.g. a custom color name) does not exist in ansi-styles (no matching export with open/close strings), the build throws, naming the offending key and value.

Example fix

// before
format(value, { highlight: true, theme: { tag: 'purple' } })
// after
format(value, { highlight: true, theme: { tag: 'magenta' } })

Defensive patterns

Strategy: validation

Validate before calling

import * as ansiStyles from 'ansi-styles'
for (const [key, value] of Object.entries(theme)) {
  if (!ansiStyles[value] || typeof ansiStyles[value].open !== 'string') {
    throw new Error(`invalid theme color '${value}' for key '${key}'`)
  }
}
format(value, { highlight: true, theme })

Type guard

function isValidThemeColor(name: string): boolean { const c = (ansiStyles as any)[name]; return !!c && typeof c.open === 'string' && typeof c.close === 'string' }

Prevention

Restrict theme values to documented ansi-styles exports
Validate theme at config load time
Avoid inventing color names not in ansi-styles

When it happens

Trigger: Passing a custom theme option with a color name not supported by ansi-styles, e.g. theme: { tag: 'purple' } where 'purple' is not an ansi-styles export; or a typo like 'reg' instead of 'red'.

Common situations: Customizing the highlight theme with an invalid color name; copy-pasting a color name from a different palette; ansi-styles version where the named export was removed/renamed.

Related errors

AI-assisted analysis of vitest-dev/vitest@1fa9837ec2 (2026-08-11). Data as JSON: /api/errors/587ee99236e0acc8. Report an issue: GitHub.

Appendix: source

Thrown at packages/pretty-format/src/index.ts:494

    throw new Error(
      'pretty-format: Options "min" and "indent" cannot be used together.',
    )
  }
}

function getColorsHighlight(): Colors {
  return DEFAULT_THEME_KEYS.reduce((colors, key) => {
    const value = DEFAULT_THEME[key]
    const color = value && (styles as any)[value]
    if (
      color
      && typeof color.close === 'string'
      && typeof color.open === 'string'
    ) {
      colors[key] = color
    }
    else {
      throw new Error(
        `pretty-format: Option "theme" has a key "${key}" whose value "${value}" is undefined in ansi-styles.`,
      )
    }
    return colors
  }, Object.create(null))
}

function getColorsEmpty(): Colors {
  return DEFAULT_THEME_KEYS.reduce((colors, key) => {
    colors[key] = { close: '', open: '' }
    return colors
  }, Object.create(null))
}

function getPrintFunctionName(options?: OptionsReceived) {
  return options?.printFunctionName ?? DEFAULT_OPTIONS.printFunctionName
}

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