Function validateXmlDeclaration

xml/_common.ts:177–381

(
  content: string,
)

 * @returns Validation result with parsed values or error message
 */
export function validateXmlDeclaration(
  content: string,
): XmlDeclarationValidationResult | XmlDeclarationValidationError {
  // Fast-path: version is required and must be first, quick check before full parse
  const trimmed = content.trimStart();
  if (!trimmed.startsWith("version")) {
    // Check for common errors: case variants
    if (
      trimmed.startsWith("VERSION") || trimmed.startsWith("Version")
    ) {
      const name = trimmed.slice(0, 7);
      return {
        valid: false,
        error: `'${name}' must be lowercase in XML declaration`,
      };
    }
    return {
      valid: false,
      error: "Missing required 'version' attribute in XML declaration",
    };
  }

  let pos = 0;
  const len = content.length;

  let version: string | undefined;
  let encoding: string | undefined;
  let standalone: "yes" | "no" | undefined;
  let foundVersion = false;
  let foundEncoding = false;
  let foundStandalone = false;

  // Skip leading whitespace
  while (pos < len && isXmlWhitespace(content.charCodeAt(pos))) {
    pos++;
  }

  // Parse attributes
  while (pos < len) {
    // Read attribute name
    const nameStart = pos;
    while (
      pos < len &&
      !isXmlWhitespace(content.charCodeAt(pos)) &&
      content.charCodeAt(pos) !== 0x3D // =
    ) {
      pos++;
    }
    const name = content.slice(nameStart, pos);

    if (name === "") {
      // Trailing whitespace only
      break;
    }

    // Check for valid attribute names and order
    if (name === "version") {
      if (foundVersion) {