Support DDC debugging tools.

lib/src/dartdevc/dartdevc.dart

Index: lib/src/dartdevc/dartdevc.dart
diff --git a/lib/src/dartdevc/dartdevc.dart b/lib/src/dartdevc/dartdevc.dart
index fb8834173726ff14a1b34acaec4488d4ca482da8..c6be0acade58743b321f1ec29032cd54e6ca8e97 100644
--- a/lib/src/dartdevc/dartdevc.dart
+++ b/lib/src/dartdevc/dartdevc.dart
@@ -4,6 +4,7 @@
 
 import 'dart:async';
 import 'dart:io';
+import 'dart:convert' show JsonEncoder;
 
 import 'package:analyzer/analyzer.dart';
 import 'package:barback/barback.dart';
@@ -13,11 +14,42 @@ import 'package:path/path.dart' as p;
 
 import '../dart.dart';
 import '../io.dart';
+import 'module.dart';
 import 'module_reader.dart';
 import 'scratch_space.dart';
 import 'summaries.dart';
 import 'workers.dart';
 
+// JavaScript snippet to determine the directory a script was run from.
+final _currentDirectoryScript = r'''
+var _currentDirectory = (function () {
+  var _url;
+  var lines = new Error().stack.split('\n');
+  function lookupUrl() {
+    if (lines.length > 2) {
+      var match = lines[1].match(/^\s+at (.+):\d+:\d+$/);
+      // Chrome.
+      if (match) return match[1];
+      // Chrome nested eval case.
+      match = lines[1].match(/^\s+at eval [(](.+):\d+:\d+[)]$/);
+      if (match) return match[1];
+      // Edge.
+      match = lines[1].match(/^\s+at.+\((.+):\d+:\d+\)$/);
+      if (match) return match[1];
+      // Firefox.
+      return lines[0].match(/[<][@](.+):\d+:\d+$/)[1];
+    }
+    // Safari.
+    return lines[0].match(/(.+):\d+:\d+$/)[1];
+  }
+  _url = lookupUrl();
+  var lastSlash = _url.lastIndexOf('/');
+  if (lastSlash == -1) return _url;
+  var currentDirectory = _url.substring(0, lastSlash + 1);
+  return currentDirectory;
+})();
+''';
+
 /// Returns whether or not [dartId] is an app entrypoint (basically, whether or
 /// not it has a `main` function).
 Future<bool> isAppEntryPoint(
@@ -90,37 +122,85 @@ Map<AssetId, Future<Asset>> bootstrapDartDevcEntrypoint(
         .join("__")
         .replaceAll('.', '\$46');
 
-    // Modules not under a `packages` directory need custom module paths.
-    var customModulePaths = <String>[];
+    // Map from module name to module path.
+    // Modules outside of the `packages` directory have different module path
+    // and module names.
+    var modulePaths = new Map<String, String>();
+    modulePaths[appModulePath] = appModulePath;
+    modulePaths['dart_sdk'] = 'dart_sdk';
+
     var transitiveDeps = await moduleReader.readTransitiveDeps(module);
     for (var dep in transitiveDeps) {
       if (dep.dir != 'lib') {
         var relativePath = p.url.relative(p.url.join(moduleDir, dep.name),
             from: p.url.dirname(bootstrapId.path));
-        customModulePaths.add('"${dep.dir}/${dep.name}": "$relativePath"');
+        var jsModuleName = '${dep.dir}/${dep.name}';
+
+        modulePaths[jsModuleName] = relativePath;
       } else {
         var jsModuleName = 'packages/${dep.package}/${dep.name}';
         var actualModulePath = p.url.relative(
             p.url.join(moduleDir, jsModuleName),
             from: p.url.dirname(bootstrapId.path));
-        if (jsModuleName != actualModulePath) {
-          customModulePaths.add('"$jsModuleName": "$actualModulePath"');
-        }
+        modulePaths[jsModuleName] = actualModulePath;
       }
     }
 
     var bootstrapContent = '''
+(function() {
+$_currentDirectoryScript
+
+let modulePaths = ${const JsonEncoder.withIndent(' ').convert(modulePaths)};
+
+if(!window.\$dartLoader) {
+   window.\$dartLoader = {
+     moduleIdToUrl: new Map(),
+     urlToModuleId: new Map(),
+     rootDirectories: new Set(),
+   };
+}
+
+let customModulePaths = {};
+window.\$dartLoader.rootDirectories.add(_currentDirectory);
+for (let moduleName of Object.getOwnPropertyNames(modulePaths)) {
+  let modulePath = modulePaths[moduleName];
+  if (modulePath != moduleName) {
+    customModulePaths[moduleName] = modulePath;
+  }
+  var src = _currentDirectory + modulePath + '.js';
+  if (window.\$dartLoader.moduleIdToUrl.has(moduleName)) {
+    continue;
+  }
+  \$dartLoader.moduleIdToUrl.set(moduleName, src);
+  \$dartLoader.urlToModuleId.set(src, moduleName);
+}
+
 require.config({
     waitSeconds: 30,
-    paths: {
-      ${customModulePaths.join(',\n      ')}
-    }
+    paths: customModulePaths
 });
 
 require(["$appModulePath", "dart_sdk"], function(app, dart_sdk) {
+  // This import is only needed for chrome debugging. We should provide an
+  // option to compile without it.
+  dart_sdk._debugger.registerDevtoolsFormatter();
+
   dart_sdk._isolate_helper.startRootIsolate(() => {}, []);
+  if (window.\$dartStackTraceUtility && !window.\$dartStackTraceUtility.ready) {
+    window.\$dartStackTraceUtility.ready = true;
+    let dart = dart_sdk.dart;
+    window.\$dartStackTraceUtility.setSourceMapProvider(
+      function(url) {
+        var module = window.\$dartLoader.urlToModuleId.get(url);
+        if (!module) return null;
+        return dart.getSourceMap(module);
+      });
+  }
+  window.postMessage({ type: "DDC_STATE_CHANGE", state: "start" }, "*");
+
   app.$appModuleScope.main();
 });
+})();
 ''';
     outputCompleters[bootstrapId]
         .complete(new Asset.fromString(bootstrapId, bootstrapContent));
@@ -129,6 +209,13 @@ require(["$appModulePath", "dart_sdk"], function(app, dart_sdk) {
         p.relative(bootstrapId.path, from: p.dirname(dartEntrypointId.path)));
     var entrypointJsContent = '''
 var el = document.createElement("script");
+el = document.createElement("script");

[jakemac, 2017/05/19 14:38:06]

duplicate code with the line right above :)

[Jacob, 2017/05/19 16:24:02]

Done.

+el.defer = true;
+el.async = false;
+el.src = "dart_stack_trace_mapper.js";
+document.head.appendChild(el);
+
+el = document.createElement("script");
 el.defer = true;
 el.async = false;
 el.src = "require.js";
@@ -191,6 +278,9 @@ Map<AssetId, Future<Asset>> createDartdevcModule(
       '--library-root=${p.dirname(jsOutputFile.path)}',
       '--summary-extension=${linkedSummaryExtension.substring(1)}',
       '--no-summarize',
+      '--source-map',

[jakemac, 2017/05/19 14:38:06]

We should only include these in DEBUG mode, a few lines below this I think I add
--no-source-map in RELEASE mode so you can share logic with that.

[Jacob, 2017/05/19 16:24:02]

Done.

+      '--source-map-comment',
+      '--inline-source-map',
       '-o',
       jsOutputFile.path,
     ]);