tailwindcss/src/lib/defaultExtractor.js

import { flagEnabled } from '../featureFlags.js'
import * as regex from './regex'

export function defaultExtractor(context) {
  let patterns = Array.from(buildRegExps(context))

  /**
   * @param {string} content
   */
  return (content) => {
    /** @type {(string|string)[]} */
    let results = []

    for (let pattern of patterns) {
      results.push(...(content.match(pattern) ?? []))
    }

    return results.filter((v) => v !== undefined).map(clipAtBalancedParens)
  }
}

function* buildRegExps(context) {
  let separator = context.tailwindConfig.separator
  let variantGroupingEnabled = flagEnabled(context.tailwindConfig, 'variantGrouping')

  yield regex.pattern([
    // Variants
    '((?=((',
    regex.any(
      [
        regex.pattern([/([^\s"'\[\\]+-)?\[[^\s"'\\]+\]/, separator]),
        regex.pattern([/[^\s"'\[\\]+/, separator]),
      ],
      true
    ),
    ')+))\\2)?',

    // Important (optional)
    /!?/,

    regex.any([
      // Arbitrary properties
      /\[[^\s:'"]+:[^\s\]]+\]/,

      // Utilities
      regex.pattern([
        // Utility Name / Group Name
        variantGroupingEnabled ? /-?(?:[\w,()]+)/ : /-?(?:\w+)/,

        // Normal/Arbitrary values
        regex.optional(
          regex.any([
            regex.pattern([
              // Arbitrary values
              /-\[[^\s:]+\]/,

              // Not immediately followed by an `{[(`
              /(?![{([]])/,

              // optionally followed by an opacity modifier
              /(?:\/[^\s'"\\$]*)?/,
            ]),

            regex.pattern([
              // Arbitrary values
              /-\[[^\s]+\]/,

              // Not immediately followed by an `{[(`
              /(?![{([]])/,

              // optionally followed by an opacity modifier
              /(?:\/[^\s'"\\$]*)?/,
            ]),

            // Normal values w/o quotes — may include an opacity modifier
            /[-\/][^\s'"\\$={]*/,
          ])
        ),
      ]),
    ]),
  ])

  // 5. Inner matches
  // yield /[^<>"'`\s.(){}[\]#=%$]*[^<>"'`\s.(){}[\]#=%:$]/g
}

// We want to capture any "special" characters
// AND the characters immediately following them (if there is one)
let SPECIALS = /([\[\]'"`])([^\[\]'"`])?/g
let ALLOWED_CLASS_CHARACTERS = /[^"'`\s<>\]]+/

/**
 * Clips a string ensuring that parentheses, quotes, etc… are balanced
 * Used for arbitrary values only
 *
 * We will go past the end of the balanced parens until we find a non-class character
 *
 * Depth matching behavior:
 * w-[calc(100%-theme('spacing[some_key][1.5]'))]']
 *   ┬    ┬          ┬┬       ┬        ┬┬   ┬┬┬┬┬┬┬
 *   1    2          3        4        34   3 210 END
 *   ╰────┴──────────┴────────┴────────┴┴───┴─┴┴┴
 *
 * @param {string} input
 */
function clipAtBalancedParens(input) {
  // We are care about this for arbitrary values
  if (!input.includes('-[')) {
    return input
  }

  let depth = 0
  let openStringTypes = []

  // Find all parens, brackets, quotes, etc
  // Stop when we end at a balanced pair
  // This is naive and will treat mismatched parens as balanced
  // This shouldn't be a problem in practice though
  let matches = input.matchAll(SPECIALS)

  // We can't use lookbehind assertions because we have to support Safari
  // So, instead, we've emulated it using capture groups and we'll re-work the matches to accommodate
  matches = Array.from(matches).flatMap((match) => {
    const [, ...groups] = match

    return groups.map((group, idx) =>
      Object.assign([], match, {
        index: match.index + idx,
        0: group,
      })
    )
  })

  for (let match of matches) {
    let char = match[0]
    let inStringType = openStringTypes[openStringTypes.length - 1]

    if (char === inStringType) {
      openStringTypes.pop()
    } else if (char === "'" || char === '"' || char === '`') {
      openStringTypes.push(char)
    }

    if (inStringType) {
      continue
    } else if (char === '[') {
      depth++
      continue
    } else if (char === ']') {
      depth--
      continue
    }

    // We've gone one character past the point where we should stop
    // This means that there was an extra closing `]`
    // We'll clip to just before it
    if (depth < 0) {
      return input.substring(0, match.index)
    }

    // We've finished balancing the brackets but there still may be characters that can be included
    // For example in the class `text-[#336699]/[.35]`
    // The depth goes to `0` at the closing `]` but goes up again at the `[`

    // If we're at zero and encounter a non-class character then we clip the class there
    if (depth === 0 && !ALLOWED_CLASS_CHARACTERS.test(char)) {
      return input.substring(0, match.index)
    }
  }

  return input
}

// Regular utilities
// {{modifier}:}*{namespace}{-{suffix}}*{/{opacityModifier}}?

// Arbitrary values
// {{modifier}:}*{namespace}-[{arbitraryValue}]{/{opacityModifier}}?
// arbitraryValue: no whitespace, balanced quotes unless within quotes, balanced brackets unless within quotes

// Arbitrary properties
// {{modifier}:}*[{validCssPropertyName}:{arbitraryValue}]