compile-coffeescript.js

import {
  SourceMapConsumer,
  SourceMapGenerator,
} from 'source-map';
import coffee from 'coffee-script';
import { BabelCompiler } from 'meteor/babel-compiler';

// The coffee-script compiler overrides Error.prepareStackTrace, mostly for the
// use of coffee.run which we don't use.  This conflicts with the tool's use of
// Error.prepareStackTrace to properly show error messages in linked code.
// Restore the tool's one after coffee-script clobbers it at import time.
if (Error.METEOR_prepareStackTrace) {
  Error.prepareStackTrace = Error.METEOR_prepareStackTrace;
}

Plugin.registerCompiler({
  extensions: ['coffee', 'litcoffee', 'coffee.md']
}, () => new CoffeeCompiler());

// The CompileResult for this CachingCompiler is a {source, sourceMap} object.

export class CoffeeCompiler extends CachingCompiler {
  constructor() {
    super({
      compilerName: 'coffeescript',
      defaultCacheSize: 1024*1024*10,
    });

    this.babelCompiler = new BabelCompiler({
      // Prevent Babel from importing helpers from babel-runtime, since
      // the CoffeeScript plugin does not imply the modules package, which
      // means require may not be defined. Note that this in no way
      // prevents CoffeeScript projects from using the modules package and
      // putting require or import statements within backticks; it just
      // won't happen automatically because of Babel.
      runtime: false
    });
  }

  _getCompileOptions(inputFile) {
    return {
      bare: true,
      filename: inputFile.getPathInPackage(),
      literate: inputFile.getExtension() !== 'coffee',
      // Return a source map.
      sourceMap: true,
      // This becomes the "file" field of the source map.
      generatedFile: '/' + this._outputFilePath(inputFile),
      // This becomes the "sources" field of the source map.
      sourceFiles: [inputFile.getDisplayPath()],
    };
  }

  _outputFilePath(inputFile) {
    return inputFile.getPathInPackage() + '.js';
  }

  getCacheKey(inputFile) {
    return [
      inputFile.getSourceHash(),
      inputFile.getDeclaredExports(),
      this._getCompileOptions(inputFile),
    ];
  }

  setDiskCacheDirectory(cacheDir) {
    this.babelCompiler.setDiskCacheDirectory(cacheDir);
    return super.setDiskCacheDirectory(cacheDir);
  }

  compileOneFile(inputFile) {
    const source = inputFile.getContentsAsString();
    const compileOptions = this._getCompileOptions(inputFile);

    let output;
    try {
      output = coffee.compile(source, compileOptions);
    } catch (e) {
      inputFile.error({
        message: e.message,
        line: e.location && (e.location.first_line + 1),
        column: e.location && (e.location.first_column + 1)
      });
      return null;
    }

    let sourceMap = JSON.parse(output.v3SourceMap);
    sourceMap.sourcesContent = [source];

    output.js = stripExportedVars(
      output.js,
      inputFile.getDeclaredExports().map(e => e.name)
    );

    // CoffeeScript contains a handful of features that output as ES2015+,
    // such as modules, generator functions, for…of, and tagged template
    // literals. Because they’re too varied to detect, pass all CoffeeScript
    // compiler output through the Babel compiler.
    const doubleRoastedCoffee =
      this.babelCompiler.processOneFileForTarget(inputFile, output.js);

    if (doubleRoastedCoffee != null &&
        doubleRoastedCoffee.data != null) {
      output.js = doubleRoastedCoffee.data;

      const coffeeSourceMap = doubleRoastedCoffee.sourceMap;

      if (coffeeSourceMap) {
        // Reference the compiled CoffeeScript file so that `applySourceMap`
        // below can match it with the source map produced by the CoffeeScript
        // compiler.
        coffeeSourceMap.sources[0] = '/' + this._outputFilePath(inputFile);

        // Combine the original CoffeeScript source map with the one
        // produced by this.babelCompiler.processOneFileForTarget.
        const smg = SourceMapGenerator.fromSourceMap(
          new SourceMapConsumer(coffeeSourceMap)
        );
        smg.applySourceMap(new SourceMapConsumer(sourceMap));
        sourceMap = smg.toJSON();
      } else {
        // If the .coffee file is contained by a node_modules directory,
        // then BabelCompiler will not transpile it, and there will be
        // no sourceMap, but that's fine because the original
        // CoffeeScript sourceMap will still be valid.
      }
    }

    return addSharedHeader(output.js, sourceMap);
  }

  addCompileResult(inputFile, sourceWithMap) {
    inputFile.addJavaScript({
      path: this._outputFilePath(inputFile),
      sourcePath: inputFile.getPathInPackage(),
      data: sourceWithMap.source,
      sourceMap: sourceWithMap.sourceMap,
      bare: inputFile.getFileOptions().bare
    });
  }

  compileResultSize(sourceWithMap) {
    return sourceWithMap.source.length +
      this.sourceMapSize(sourceWithMap.sourceMap);
  }
}

function stripExportedVars(source, exports) {
  if (!exports || !exports.length)
    return source;
  const lines = source.split("\n");

  // We make the following assumptions, based on the output of CoffeeScript
  // 1.7.1.
  //   - The var declaration in question is not indented and is the first such
  //     var declaration.  (CoffeeScript only produces one var line at each
  //     scope and there's only one top-level scope.)  All relevant variables
  //     are actually on this line.
  //   - The user hasn't used a ###-comment containing a line that looks like
  //     a var line, to produce something like
  //        /* bla
  //        var foo;
  //        */
  //     before an actual var line.  (ie, we do NOT attempt to figure out if
  //     we're inside a /**/ comment, which is produced by ### comments.)
  //   - The var in question is not assigned to in the declaration, nor are any
  //     other vars on this line. (CoffeeScript does produce some assignments
  //     but only for internal helpers generated by CoffeeScript, and they end
  //     up on subsequent lines.)
  // XXX relax these assumptions by doing actual JS parsing (eg with jsparse).
  //     I'd do this now, but there's no easy way to "unparse" a jsparse AST.
  //     Or alternatively, hack the compiler to allow us to specify unbound
  //     symbols directly.

  for (let i = 0; i < lines.length; i++) {
    const line = lines[i];
    const match = /^var (.+)([,;])$/.exec(line);
    if (!match)
      continue;

    // If there's an assignment on this line, we assume that there are ONLY
    // assignments and that the var we are looking for is not declared. (Part
    // of our strong assumption about the layout of this code.)
    if (match[1].indexOf('=') !== -1)
      continue;

    // We want to replace the line with something no shorter, so that all
    // records in the source map continue to point at valid
    // characters.
    function replaceLine(x) {
      if (x.length >= lines[i].length) {
        lines[i] = x;
      } else {
        lines[i] = x + new Array(1 + (lines[i].length - x.length)).join(' ');
      }
    }

    let vars = match[1].split(', ').filter(v => exports.indexOf(v) === -1);
    if (vars.length) {
      replaceLine('var ' + vars.join(', ') + match[2]);
    } else {
      // We got rid of all the vars on this line. Drop the whole line if this
      // didn't continue to the next line, otherwise keep just the 'var '.
      if (match[2] === ';')
        replaceLine('');
      else
        replaceLine('var');
    }
    break;
  }

  return lines.join('\n');
}

function addSharedHeader(source, sourceMap) {
  // We want the symbol "share" to be visible to all CoffeeScript files in the
  // package (and shared between them), but not visible to JavaScript
  // files. (That's because we don't want to introduce two competing ways to
  // make package-local variables into JS ("share" vs assigning to non-var
  // variables).) The following hack accomplishes that: "__coffeescriptShare"
  // will be visible at the package level and "share" at the file level.  This
  // should work both in "package" mode where __coffeescriptShare will be added
  // as a var in the package closure, and in "app" mode where it will end up as
  // a global.
  //
  // This ends in a newline to make the source map easier to adjust.
  const header = ("__coffeescriptShare = typeof __coffeescriptShare === 'object' " +
                  "? __coffeescriptShare : {}; " +
                  "var share = __coffeescriptShare;\n");

  // If the file begins with "use strict", we need to keep that as the first
  // statement.
  const processedSource = source.replace(/^(?:((['"])use strict\2;)\n)?/, (match, useStrict) => {
    if (match) {
      // There's a "use strict"; we keep this as the first statement and insert
      // our header at the end of the line that it's on. This doesn't change
      // line numbers or the part of the line that previous may have been
      // annotated, so we don't need to update the source map.
      return useStrict + '  ' + header;
    } else {
      // There's no use strict, so we can just add the header at the very
      // beginning. This adds a line to the file, so we update the source map to
      // add a single un-annotated line to the beginning.
      sourceMap.mappings = ';' + sourceMap.mappings;
      return header;
    }
  });
  return {
    source: processedSource,
    sourceMap: sourceMap
  };
}