Function highlightCodeBlock

src/common/syntax-highlighter.ts:356–418

(
  code: string,
  lineStart: number | undefined = 1,
  markIndicator?: string,
  grammar?: SyntaxGrammar
)

 * gutter with line numbers and an optional highlighted line
 */
export function highlightCodeBlock(
  code: string,
  lineStart: number | undefined = 1,
  markIndicator?: string,
  grammar?: SyntaxGrammar
): StyledBlock {
  // Split the mark into a line and column range
  // e.g 14:3-14 -> { line: 14, colStart: 3, colEnd: 14 }
  let markLine = 0;
  let markCol = '';
  if (markIndicator) {
    let lineStr = '';
    [lineStr, markCol] = markIndicator.split(':');
    markLine = parseInt(lineStr);
  }

  // Split the code into lines
  const sourceLines = code.split('\n');

  // Parse each line
  const lines = sourceLines.map((line) => renderCode(parseCode(line, grammar)));

  if (lineStart === undefined) {
    // Concatenate the lines into a single block without a gutter
    const content = lines.flatMap((line) => [...line, { content: '\n' }]);
    return { tag: 'block', spans: content };
  }

  // Turn the lines into a StyleBlock
  const lastLine = lineStart + sourceLines.length - 1;
  const maxDigits = lastLine.toString().length;

  // Return a StyleBlock with a gutter including line numbers

  const content: StyledSpan[] = lines.flatMap((line, i) => {
    const lineNo = lineStart + i;
    if (lineNo === markLine) {
      return [
        {
          content: `\n${lineNo.toString().padStart(maxDigits, ' ')} `,
          weight: 'normal',
          ...DEFAULT_THEME.mark,
        },
        {
          content: `\u2503`,
          ...DEFAULT_THEME.mark_indicator,
        },
        ...mark(line, markCol),
      ];
    } else {
      const lineNoStr = `\n${lineNo.toString().padStart(maxDigits, ' ')}`;
      return [
        { content: lineNoStr, weight: 'thin' },
        { content: ' \u2502 ', fg: 'white' }, // U+2502 Thin vertical line
        ...line,
      ];
    }
  });