parcel-bundler/src/assets/JSAsset.js

Blazing fast, zero configuration web application bundler

const traverse = require('@babel/traverse').default;
const codeFrame = require('@babel/code-frame').codeFrameColumns;
const collectDependencies = require('../visitors/dependencies');
const walk = require('babylon-walk');
const Asset = require('../Asset');
const babelParser = require('@babel/parser');
const insertGlobals = require('../visitors/globals');
const fsVisitor = require('../visitors/fs');
const envVisitor = require('../visitors/env');
const babel = require('../transforms/babel/transform');
const babel7 = require('../transforms/babel/babel7');
const generate = require('@babel/generator').default;
const terser = require('../transforms/terser');
const SourceMap = require('../SourceMap');
const hoist = require('../scope-hoisting/hoist');
const path = require('path');
const fs = require('../utils/fs');
const logger = require('../Logger');

const IMPORT_RE = /\b(?:import\b|export\b|require\s*\()/;
const ENV_RE = /\b(?:process\.env)\b/;
const GLOBAL_RE = /\b(?:process|__dirname|__filename|global|Buffer|define)\b/;
const FS_RE = /\breadFileSync\b/;
const SW_RE = /\bnavigator\s*\.\s*serviceWorker\s*\.\s*register\s*\(/;
const WORKER_RE = /\bnew\s*(?:Shared)?Worker\s*\(/;
const SOURCEMAP_RE = /\/\/\s*[@#]\s*sourceMappingURL\s*=\s*([^\s]+)/;
const DATA_URL_RE = /^data:[^;]+(?:;charset=[^;]+)?;base64,(.*)/;

class JSAsset extends Asset {
  constructor(name, options) {
    super(name, options);
    this.type = 'js';
    this.globals = new Map();
    this.isAstDirty = false;
    this.isES6Module = false;
    this.outputCode = null;
    this.cacheData.env = {};
    this.rendition = options.rendition;
    this.sourceMap = this.rendition ? this.rendition.sourceMap : null;
  }

  shouldInvalidate(cacheData) {
    for (let key in cacheData.env) {
      if (cacheData.env[key] !== process.env[key]) {
        return true;
      }
    }

    return false;
  }

  mightHaveDependencies() {
    return (
      this.isAstDirty ||
      !/.js$/.test(this.name) ||
      IMPORT_RE.test(this.contents) ||
      GLOBAL_RE.test(this.contents) ||
      SW_RE.test(this.contents) ||
      WORKER_RE.test(this.contents)
    );
  }

  async parse(code) {
    return babelParser.parse(code, {
      filename: this.name,
      allowReturnOutsideFunction: true,
      strictMode: false,
      sourceType: 'module',
      plugins: ['exportDefaultFrom', 'exportNamespaceFrom', 'dynamicImport']
    });
  }

  traverse(visitor) {
    return traverse(this.ast, visitor, null, this);
  }

  traverseFast(visitor) {
    return walk.simple(this.ast, visitor, this);
  }

  collectDependencies() {
    walk.ancestor(this.ast, collectDependencies, this);
  }

  async loadSourceMap() {
    // Get original sourcemap if there is any
    let match = this.contents.match(SOURCEMAP_RE);
    if (match) {
      this.contents = this.contents.replace(SOURCEMAP_RE, '');

      let url = match[1];
      let dataURLMatch = url.match(DATA_URL_RE);

      try {
        let json, filename;
        if (dataURLMatch) {
          filename = this.name;
          json = new Buffer(dataURLMatch[1], 'base64').toString();
        } else {
          filename = path.join(path.dirname(this.name), url);
          json = await fs.readFile(filename, 'utf8');

          // Add as a dep so we watch the source map for changes.
          this.addDependency(filename, {includedInParent: true});
        }

        this.sourceMap = JSON.parse(json);

        // Attempt to read missing source contents
        if (!this.sourceMap.sourcesContent) {
          this.sourceMap.sourcesContent = [];
        }

        let missingSources = this.sourceMap.sources.slice(
          this.sourceMap.sourcesContent.length
        );
        if (missingSources.length) {
          let contents = await Promise.all(
            missingSources.map(async source => {
              try {
                let sourceFile = path.join(
                  path.dirname(filename),
                  this.sourceMap.sourceRoot || '',
                  source
                );
                let result = await fs.readFile(sourceFile, 'utf8');
                this.addDependency(sourceFile, {includedInParent: true});
                return result;
              } catch (err) {
                logger.warn(
                  `Could not load source file "${source}" in source map of "${
                    this.relativeName
                  }".`
                );
              }
            })
          );

          this.sourceMap.sourcesContent = this.sourceMap.sourcesContent.concat(
            contents
          );
        }
      } catch (e) {
        logger.warn(
          `Could not load existing sourcemap of "${this.relativeName}".`
        );
      }
    }
  }

  async pretransform() {
    if (this.options.sourceMaps) {
      await this.loadSourceMap();
    }

    await babel(this);

    // Inline environment variables
    if (this.options.target === 'browser' && ENV_RE.test(this.contents)) {
      await this.parseIfNeeded();
      this.traverseFast(envVisitor);
    }
  }

  async transform() {
    if (this.options.target === 'browser') {
      if (this.dependencies.has('fs') && FS_RE.test(this.contents)) {
        // Check if we should ignore fs calls
        // See https://github.com/defunctzombie/node-browser-resolve#skip
        let pkg = await this.getPackage();
        let ignore = pkg && pkg.browser && pkg.browser.fs === false;

        if (!ignore) {
          await this.parseIfNeeded();
          this.traverse(fsVisitor);
        }
      }

      if (GLOBAL_RE.test(this.contents)) {
        await this.parseIfNeeded();
        walk.ancestor(this.ast, insertGlobals, this);
      }
    }

    if (this.options.scopeHoist) {
      await this.parseIfNeeded();
      await this.getPackage();

      this.traverse(hoist);
      this.isAstDirty = true;
    } else {
      if (this.isES6Module) {
        await babel7(this, {
          internal: true,
          config: {
            plugins: [require('@babel/plugin-transform-modules-commonjs')]
          }
        });
      }
    }

    if (this.options.minify) {
      await terser(this);
    }
  }

  async generate() {
    let enableSourceMaps =
      this.options.sourceMaps &&
      (!this.rendition || !!this.rendition.sourceMap);
    let code;
    if (this.isAstDirty) {
      let opts = {
        sourceMaps: this.options.sourceMaps,
        sourceFileName: this.relativeName
      };

      let generated = generate(this.ast, opts, this.contents);

      if (enableSourceMaps && generated.rawMappings) {
        let rawMap = new SourceMap(generated.rawMappings, {
          [this.relativeName]: this.contents
        });

        // Check if we already have a source map (e.g. from TypeScript or CoffeeScript)
        // In that case, we need to map the original source map to the babel generated one.
        if (this.sourceMap) {
          this.sourceMap = await new SourceMap().extendSourceMap(
            this.sourceMap,
            rawMap
          );
        } else {
          this.sourceMap = rawMap;
        }
      }

      code = generated.code;
    } else {
      code = this.outputCode != null ? this.outputCode : this.contents;
    }

    if (enableSourceMaps && !this.sourceMap) {
      this.sourceMap = new SourceMap().generateEmptyMap(
        this.relativeName,
        this.contents
      );
    }

    if (this.globals.size > 0) {
      code = Array.from(this.globals.values()).join('\n') + '\n' + code;
      if (enableSourceMaps) {
        if (!(this.sourceMap instanceof SourceMap)) {
          this.sourceMap = await new SourceMap().addMap(this.sourceMap);
        }

        this.sourceMap.offset(this.globals.size);
      }
    }

    return {
      js: code,
      map: this.sourceMap
    };
  }

  generateErrorMessage(err) {
    const loc = err.loc;
    if (loc) {
      // Babel 7 adds its own code frame on the error message itself
      // We need to remove it and pass it separately.
      if (err.message.startsWith(this.name)) {
        err.message = err.message
          .slice(this.name.length + 1, err.message.indexOf('\n'))
          .trim();
      }

      err.codeFrame = codeFrame(this.contents, {start: loc});
      err.highlightedCodeFrame = codeFrame(
        this.contents,
        {start: loc},
        {highlightCode: true}
      );
    }

    return err;
  }
}

module.exports = JSAsset;