parse-example-file.ts

import ts from 'typescript';

interface ParsedMetadata {
  isPrimary: boolean;
  componentName: string;
  title: string;
  selector: string;
  templateUrl: string;
  styleUrls: string[];
}

interface ParsedMetadataResults {
  primaryComponent: ParsedMetadata | undefined;
  secondaryComponents: ParsedMetadata[];
}

/** Parse the AST of the given source file and collect Angular component metadata. */
export function parseExampleFile(fileName: string, content: string): ParsedMetadataResults {
  const sourceFile = ts.createSourceFile(fileName, content, ts.ScriptTarget.Latest, false);
  const metas: ParsedMetadata[] = [];

  const visitNode = (node: any): void => {
    if (node.kind === ts.SyntaxKind.ClassDeclaration) {
      const decorators = ts.getDecorators(node);
      const meta = {
        componentName: node.name.text,
      } as ParsedMetadata;

      if (node.jsDoc && node.jsDoc.length) {
        for (const doc of node.jsDoc) {
          if (doc.tags && doc.tags.length) {
            for (const tag of doc.tags) {
              const tagValue = tag.comment;
              const tagName = tag.tagName.text;
              if (tagName === 'title') {
                meta.title = tagValue;
                meta.isPrimary = true;
              }
            }
          }
        }
      }

      if (decorators && decorators.length) {
        for (const decorator of decorators) {
          const call = decorator.expression;

          if (
            !ts.isCallExpression(call) ||
            !ts.isIdentifier(call.expression) ||
            call.expression.text !== 'Component' ||
            call.arguments.length === 0 ||
            !ts.isObjectLiteralExpression(call.arguments[0])
          ) {
            continue;
          }

          for (const prop of call.arguments[0].properties) {
            if (!ts.isPropertyAssignment(prop) || !prop.name || !ts.isIdentifier(prop.name)) {
              continue;
            }

            const propName = prop.name.text;

            // Since additional files can be also stylesheets, we need to properly parse
            // the styleUrls metadata property.
            if (propName === 'styleUrls' && ts.isArrayLiteralExpression(prop.initializer)) {
              meta[propName] = prop.initializer.elements.map(
                literal => (literal as ts.StringLiteralLike).text,
              );
            } else if (propName === 'styleUrl' && ts.isStringLiteralLike(prop.initializer)) {
              meta.styleUrls = [prop.initializer.text];
            } else if (
              ts.isStringLiteralLike(prop.initializer) ||
              ts.isIdentifier(prop.initializer)
            ) {
              (meta as any)[propName] = prop.initializer.text;
            }
          }

          metas.push(meta);
        }
      }
    }

    ts.forEachChild(node, visitNode);
  };

  visitNode(sourceFile);

  return {
    primaryComponent: metas.find(m => m.isPrimary),
    secondaryComponents: metas.filter(m => !m.isPrimary),
  };
}