lib/src/codegen/js_printer.dart

// Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

import 'dart:convert' show JSON, JsonEncoder;
import 'dart:io' show Directory, File, Platform, Process;

import 'package:analyzer/src/generated/ast.dart';
import 'package:path/path.dart' as path;
import 'package:source_maps/source_maps.dart' as srcmaps show Printer;
import 'package:source_maps/source_maps.dart' show SourceMapSpan;
import 'package:source_span/source_span.dart' show SourceLocation;

import '../js/js_ast.dart' as JS;
import '../utils.dart' show computeHash, locationForOffset;

import 'js_names.dart' show TemporaryNamer;

String writeJsLibrary(
    JS.Program jsTree, String outputPath, String inputDir, Uri serverUri,
    {bool emitSourceMaps: false}) {
  var outFilename = path.basename(outputPath);
  var outDir = path.dirname(outputPath);
  new Directory(outDir).createSync(recursive: true);

  JS.JavaScriptPrintingContext context;
  if (emitSourceMaps) {
    var printer = new srcmaps.Printer(outFilename);
    context =
        new SourceMapPrintingContext(printer, outDir, inputDir, serverUri);
  } else {
    context = new JS.SimpleJavaScriptPrintingContext();
  }

  var opts = new JS.JavaScriptPrintingOptions(
      allowKeywordsInProperties: true, allowSingleLineIfStatements: true);
  var jsNamer = new TemporaryNamer(jsTree);
  jsTree.accept(new JS.Printer(opts, context, localNamer: jsNamer));

  String text;
  if (context is SourceMapPrintingContext) {
    var printer = context.printer;
    printer.add('//# sourceMappingURL=$outFilename.map\n');
    // Write output file and source map
    text = printer.text;
    var sourceMap = JSON.decode(printer.map);
    var sourceMapText = new JsonEncoder.withIndent('  ').convert(sourceMap);
    // Convert:
    //   "names": [
    //     "state",
    //     "print"
    //   ]
    // to:
    //   "names": ["state","print"]
    sourceMapText =
        sourceMapText.replaceAll('\n    ', '').replaceAll('\n  ]', ']');
    new File('$outputPath.map').writeAsStringSync('$sourceMapText\n');
  } else {
    text = (context as JS.SimpleJavaScriptPrintingContext).getText();
  }
  new File(outputPath).writeAsStringSync(text);
  if (jsTree.scriptTag != null) {
    // Mark executable.
    // TODO(jmesserly): should only do this if the input file was executable?
    if (!Platform.isWindows) Process.runSync('chmod', ['+x', outputPath]);
  }

  return computeHash(text);
}

class SourceMapPrintingContext extends JS.JavaScriptPrintingContext {
  final srcmaps.Printer printer;
  final String outputDir;
  final String inputDir;

  // TODO(vsm): we could abstract this out and have a generic Uri mapping
  // instead of hardcoding a notion of a server uri.
  final Uri serverUri;

  CompilationUnit unit;
  Uri uri;

  SourceMapPrintingContext(
      this.printer, this.outputDir, this.inputDir, this.serverUri);

  void emit(String string) {
    printer.add(string);
  }

  AstNode _currentTopLevelDeclaration;

  void enterNode(JS.Node jsNode) {
    AstNode node = jsNode.sourceInformation;
    if (node == null || node.offset == -1) return;
    if (unit == null) {
      // This is a top-level declaration.  Note: consecutive top-level
      // declarations may come from different compilation units due to
      // parts.
      _currentTopLevelDeclaration = node;
      unit = node.getAncestor((n) => n is CompilationUnit);
      uri = _makeRelativeUri(unit.element.source.uri);
    }
    if (unit == null) return;

    assert(unit != null);
    var loc = _location(node.offset);
    var name = _getIdentifier(node);
    if (name != null) {
      // TODO(jmesserly): mark only uses the beginning of the span, but
      // we're required to pass this as a valid span.
      var end = _location(node.end);
      printer.mark(new SourceMapSpan(loc, end, name, isIdentifier: true));
    } else {
      printer.mark(loc);
    }
  }

  SourceLocation _location(int offset) =>
      locationForOffset(unit.lineInfo, uri, offset);

  Uri _makeRelativeUri(Uri src) {
    if (serverUri == null) {
      return new Uri(path: path.relative(src.path, from: outputDir));
    } else {
      if (src.path.startsWith('/')) {
        return serverUri.resolve(path.relative(src.path, from: inputDir));
      } else {
        return serverUri.resolve(path.join('packages', src.path));
      }
    }
  }

  void exitNode(JS.Node jsNode) {
    AstNode node = jsNode.sourceInformation;
    if (unit == null || node == null || node.offset == -1) return;

    // TODO(jmesserly): in many cases marking the end will be unnecessary.
    printer.mark(_location(node.end));

    if (_currentTopLevelDeclaration == node) {
      unit = null;
      uri = null;
      _currentTopLevelDeclaration == null;
      return;
    }
  }

  String _getIdentifier(AstNode node) {
    if (node is SimpleIdentifier) return node.name;
    return null;
  }
}