old_contents: import buildSelectorVariant from '../util/buildSelectorVariant'
  import defaultConfig from '../../defaultConfig'
  
  export default {
    dark: 'media',
    variants: {
      backgroundColor: [...defaultConfig.variants.backgroundColor, 'dark'],
      gradientColorStops: [...defaultConfig.variants.gradientColorStops, 'dark'],
      borderColor: [...defaultConfig.variants.borderColor, 'dark'],
      divideColor: [...defaultConfig.variants.divideColor, 'dark'],
      placeholderColor: [...defaultConfig.variants.placeholderColor, 'dark'],
      textColor: [...defaultConfig.variants.textColor, 'dark'],
    },
    plugins: [
      function({ addVariant, config, postcss, prefix }) {
        addVariant('dark', ({ container, separator, modifySelectors }) => {
          if (config('dark') === 'media') {
            const modified = modifySelectors(({ selector }) => {
              return buildSelectorVariant(selector, 'dark', separator, message => {
                throw container.error(message)
              })
            })
            const mediaQuery = postcss.atRule({
              name: 'media',
              params: '(prefers-color-scheme: dark)',
            })
            mediaQuery.append(modified)
            container.append(mediaQuery)
            return container
          }
  
          if (config('dark') === 'class') {
            const modified = modifySelectors(({ selector }) => {
              return buildSelectorVariant(selector, 'dark', separator, message => {
                throw container.error(message)
              })
            })
  
            modified.walkRules(rule => {
              rule.selectors = rule.selectors.map(selector => {
                return `${prefix('.dark ')} ${selector}`
              })
            })
  
            return modified
          }
  
          throw new Error("The `dark` config option must be either 'media' or 'class'.")
        })
      },
    ],
  }
  
new_contents: import buildSelectorVariant from '../util/buildSelectorVariant'
  import defaultConfig from '../../defaultConfig'
  
  export default {
    dark: 'media',
    variants: {
      backgroundColor: [...defaultConfig.variants.backgroundColor, 'dark'],
      gradientColorStops: [...defaultConfig.variants.gradientColorStops, 'dark'],
      borderColor: [...defaultConfig.variants.borderColor, 'dark'],
      divideColor: [...defaultConfig.variants.divideColor, 'dark'],
      placeholderColor: [...defaultConfig.variants.placeholderColor, 'dark'],
      textColor: [...defaultConfig.variants.textColor, 'dark'],
    },
    plugins: [
      function({ addVariant, config, postcss, prefix }) {
        addVariant('dark', ({ container, separator, modifySelectors }) => {
          if (config('dark') === 'media') {
            const modified = modifySelectors(({ selector }) => {
              return buildSelectorVariant(selector, 'dark', separator, message => {
                throw container.error(message)
              })
            })
            const mediaQuery = postcss.atRule({
              name: 'media',
              params: '(prefers-color-scheme: dark)',
            })
            mediaQuery.append(modified)
            container.append(mediaQuery)
            return container
          }
  
          if (config('dark') === 'class') {
            const modified = modifySelectors(({ selector }) => {
              return buildSelectorVariant(selector, 'dark', separator, message => {
                throw container.error(message)
              })
            })
  
            modified.walkRules(rule => {
              rule.selectors = rule.selectors.map(selector => {
                return `${prefix('.dark')} ${selector}`
              })
            })
  
            return modified
          }
  
          throw new Error("The `dark` config option must be either 'media' or 'class'.")
        })
      },
    ],
  }
  
subject: Remove extra space character