front_end/models/text_utils/CodeMirrorUtils.ts

// Copyright 2022 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

import * as CodeMirror from '../../third_party/codemirror.next/codemirror.next.js';

type Tokenizer = (line: string, callback: (value: string, style: string|null) => void) => Promise<void>;

export function createCssTokenizer(): Tokenizer {
  async function tokenize(line: string, callback: (value: string, style: string|null) => void): Promise<void> {
    const streamParser = await CodeMirror.cssStreamParser();
    const stream = new CodeMirror.StringStream(line, 4, 2);

    const state = streamParser.startState(2);
    let lastPos = stream.pos;
    while (!stream.eol()) {
      stream.start = lastPos;
      let tokenType = streamParser.token(stream, state);
      /**
       * We expect unknown properties (like `unknownProp: unknownPropVal`) to still be
       * formatted correctly. However, `tokenType` for such properties are marked
       * as `error` from CodeMirror side and the internal state of the parser becomes `maybeprop`.
       *
       * So, we handle that specific keyword to be marked as `property` even though it is
       * not a known property. We do this because for our formatting purposes it doesn't matter
       * whether a property is a known CSS property or not.
       */
      if (tokenType === 'error' && state.state === 'maybeprop') {
        tokenType = 'property';
      }
      const segment = stream.current();
      callback(segment, tokenType);
      lastPos = stream.pos;
    }
  }
  return tokenize;
}