Function validateSwitchBlock

packages/compiler/src/render3/r3_control_flow.ts:599–654

Checks that the shape of a `switch` block is valid. Returns an array of errors.

(ast: html.Block)

/** Checks that the shape of a `switch` block is valid. Returns an array of errors. */
function validateSwitchBlock(ast: html.Block): ParseError[] {
  const errors: ParseError[] = [];
  let hasDefault = false;

  if (ast.parameters.length !== 1) {
    errors.push(
      new ParseError(ast.startSourceSpan, '@switch block must have exactly one parameter'),
    );
    return errors;
  }

  for (const node of ast.children) {
    // Skip over comments and empty text nodes inside the switch block.
    // Empty text nodes can be used for formatting while comments don't affect the runtime.
    if (
      node instanceof html.Comment ||
      (node instanceof html.Text && node.value.trim().length === 0)
    ) {
      continue;
    }

    if (
      !(node instanceof html.Block) ||
      (node.name !== 'case' && node.name !== 'default' && node.name !== 'default never')
    ) {
      errors.push(
        new ParseError(node.sourceSpan, '@switch block can only contain @case and @default blocks'),
      );
      continue;
    }

    if (node.name === 'default never') {
      if (hasDefault) {
        errors.push(
          new ParseError(node.startSourceSpan, '@switch block can only have one @default block'),
        );
      }
      hasDefault = true;
    } else if (node.name === 'default') {
      if (hasDefault) {
        errors.push(
          new ParseError(node.startSourceSpan, '@switch block can only have one @default block'),
        );
      } else if (node.parameters.length > 0) {
        errors.push(new ParseError(node.startSourceSpan, '@default block cannot have parameters'));
      }
      hasDefault = true;
    } else if (node.name === 'case' && node.parameters.length !== 1) {
      errors.push(
        new ParseError(node.startSourceSpan, '@case block must have exactly one parameter'),
      );
    }
  }

  return errors;
}

/**