assetgraph/lib/parseJavaScript.js

An auto discovery dependency graph based optimization framework for web pages and applications

const acorn = require('acorn');
const Parser = acorn.Parser.extend(require('acorn-jsx')());
const estraverse = require('estraverse');

// From espree
function convertAcornCommentToEsprimaComment(
  block,
  text,
  start,
  end,
  startLoc,
  endLoc
) {
  const comment = {
    type: block ? 'Block' : 'Line',
    value: text
  };

  if (typeof start === 'number') {
    comment.start = start;
    comment.end = end;
    comment.range = [start, end];
  }

  if (typeof startLoc === 'object') {
    comment.loc = {
      start: startLoc,
      end: endLoc
    };
  }

  return comment;
}

function parseJavaScript(code, options = {}) {
  const comments = [];
  const tokens = [];
  const parser = new Parser(
    {
      ...options,
      // Collect comments
      onComment(block, text, start, end, startLoc, endLoc) {
        comments.push(
          convertAcornCommentToEsprimaComment(
            block,
            text,
            start,
            end,
            startLoc,
            endLoc
          )
        );
      },
      onToken(token) {
        tokens.push(token);
      }
    },
    code
  );

  const ast = parser.parse();
  ast.comments = comments;
  ast.tokens = tokens;
  const lastToken = tokens.pop();
  // Adjustments from espree:
  if (ast.range) {
    ast.range[0] = ast.body.length ? ast.body[0].range[0] : ast.range[0];
    ast.range[1] = lastToken ? lastToken.range[1] : ast.range[1];
  }
  if (ast.loc) {
    ast.loc.start = ast.body.length ? ast.body[0].loc.start : ast.loc.start;
    ast.loc.end = lastToken ? lastToken.loc.end : ast.loc.end;
  }

  if (options.locations && options.ranges) {
    estraverse.attachComments(ast, ast.comments, ast.tokens);
  }
  return ast;
}

module.exports = parseJavaScript;