Code coverage, something is working now.

pkg/analyzer_experimental/lib/src/services/runtime/coverage/models.dart

+// Copyright (c) 2013, 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.
+
+/// A library with code coverage models.
+library runtime.coverage.model;
+
+import 'dart:collection' show SplayTreeMap;
+
+import 'package:analyzer_experimental/src/generated/source.dart' show Source, SourceRange;
+import 'package:analyzer_experimental/src/generated/ast.dart' show ASTNode;
+
+import 'utils.dart';
+
+
+/// Contains information about the application.
+class AppInfo {
+  final List<NodeInfo> nodeStack = new List<NodeInfo>();

[Bob Nystrom, 2013/06/17 21:30:12]

final nodeStack = <NodeInfo>[];

Ditto for other fields.

[scheglov, 2013/06/17 22:30:57]

For all fields or for final fields with initializers?

Actually 'nextId' also has initializer.
But 'currentNode' is assigned 'null', so it is not obvious which type it is.

[Bob Nystrom, 2013/06/17 22:44:41]

Just ones with initializers. If they aren't initialized, it's good to annotate
them.
Yup. Annotate this, but I wouldn't bother to initialize it to null since it does
that implicitly.

+  final List<UnitInfo> units = new List<UnitInfo>();
+  final Map<String, UnitInfo> pathToFile = new Map<String, UnitInfo>();
+  NodeInfo currentNode = null;
+  int nextId = 0;
+
+  void enterUnit(String path, String content) {
+    var unit = new UnitInfo(this, path, content);
+    units.add(unit);
+    currentNode = unit;
+  }
+
+  void enter(String kind, String name) {
+    nodeStack.add(currentNode);
+    currentNode = new NodeInfo(this, currentNode, kind, name);
+  }
+
+  void leave() {
+    currentNode = nodeStack.removeLast();
+  }
+
+  int addNode(ASTNode node) {
+    return currentNode.addNode(node);
+  }
+
+  void print(StringSink sink, Set<int> executedIds) {

[Bob Nystrom, 2013/06/17 21:30:12]

Calling a method "print" is probably asking for trouble. If you just do
"print()" inside another method in this class, it will call the top-level
print() function and not this one since lexical scope takes priority over
members in Dart.

[scheglov, 2013/06/17 22:30:57]

Ah... yes.
Renamed to 'write'.

+    sink.writeln('{');
+    units.asMap().forEach((int i, UnitInfo unit) {
+      if (i != 0) sink.writeln(',');
+      unit.print(sink, executedIds, '  ');
+    });
+    sink.writeln();
+    sink.writeln('}');
+  }
+}
+
+/// Information about some node - unit, class, method, function.
+class NodeInfo {
+  final AppInfo appInfo;
+  final NodeInfo parent;
+  final String kind;
+  final String name;
+  final Map<int, SourceRange> idToRange = new SplayTreeMap<int, SourceRange>();
+  final List<NodeInfo> children = <NodeInfo> [];

[Bob Nystrom, 2013/06/17 21:30:12]

No space between > and [

[scheglov, 2013/06/17 22:30:57]

Done.

+
+  NodeInfo(this.appInfo, this.parent, this.kind, this.name) {
+    if (parent != null) {
+      parent.children.add(this);
+    }
+  }
+
+  int addNode(ASTNode node) {
+    var id = appInfo.nextId++;
+    var range = new SourceRange(node.offset, node.length);
+    idToRange[id] = range;
+    return id;
+  }
+
+  void print(StringSink sink, Set<int> executedIds, String prefix) {
+    sink.writeln('$prefix"$name": {');
+    // Kind.
+    sink.writeln('$prefix  "kind": "$kind",');
+    // Print children.
+    if (children.isNotEmpty) {

[Bob Nystrom, 2013/06/17 21:30:12]

Today I learned Iterable has isNotEmpty! :)

+      sink.writeln('$prefix  "children": {');
+      children.asMap().forEach((int i, NodeInfo child) {

[scheglov, 2013/06/17 22:30:57]

Is it recommended to have type annotations for closure parameters or skip them?

[Bob Nystrom, 2013/06/17 22:44:41]

The style guide says: "AVOID annotating types on function expressions."

I'm assuming at some point you'll add inference for them so we don't have to
annotate. :)

[scheglov, 2013/06/18 06:11:04]

Done.

+        if (i != 0) sink.writeln(',');
+        children[i].print(sink, executedIds, '$prefix    ');
+      });

[Bob Nystrom, 2013/06/17 21:30:12]

Clever! You could also try:

children.fold(null, (prev, child) {
  if (prev != null) sink.writeln(',');
  child.print(sink, executedIds, '$prefix    ');
  return child;
});

That shouldn't have the overhead of creating the map.

[scheglov, 2013/06/17 22:30:57]

  More lines of code - I have to add "return" :-(
  Or use cascade trick:
return child..print(sink, executedIds, '$prefix    ');

  May be worth to write some helper.
  As I understand, there almost for sure was discussion to add forEach with
index into library and if it is not there, then there are no chance to get it.

+      sink.writeln();
+      sink.writeln('$prefix  }');
+    }
+    // Print source and line ranges.
+    if (children.isEmpty) {
+      sink.write('${prefix}  "ranges": [');
+      var rangePrinter = new RangePrinter(unit, sink, executedIds);
+      idToRange.forEach(rangePrinter.handle);

[Bob Nystrom, 2013/06/17 21:30:12]

Nice.

+      rangePrinter.printRange();
+      sink.writeln(']');
+    }
+    // Close this node.
+    sink.write('$prefix}');
+  }
+
+  UnitInfo get unit => parent.unit;
+}
+
+/// Helper for printing merged source/line intervals.
+class RangePrinter {
+  final UnitInfo unit;
+  final StringSink sink;
+  final Set<int> executedIds;
+
+  bool first = true;
+  int startId = -1;
+  int startOffset = -1;
+  int endId = -1;
+  int endOffset = -1;
+
+  RangePrinter(this.unit, this.sink, this.executedIds);
+
+  handle(int id, SourceRange range) {
+    if (executedIds.contains(id)) {
+      printRange();
+    } else {
+      if (endId == id - 1) {
+        endId = id;
+        endOffset = range.end;
+      } else {
+        startId = id;
+        endId = id;
+        startOffset = range.offset;
+        endOffset = range.end;
+      }
+    }
+  }
+
+  void printRange() {
+    if (endId == -1) return;
+    printSeparator();
+    var startLine = unit.getLine(startOffset);
+    var endLine = unit.getLine(endOffset);
+    sink.write('$startOffset,$endOffset,$startLine,$endLine');
+    startId = startOffset = startLine = -1;
+    endId = endOffset = endLine = -1;
+  }
+
+  void printSeparator() {
+    if (first) {
+      first = false;
+    } else {
+      sink.write(', ');
+    }
+  }
+}
+
+/// Containts information about the single unit of the application.

[Bob Nystrom, 2013/06/17 21:30:12]

Containts -> Contains.

[scheglov, 2013/06/17 22:30:57]

Done.

+class UnitInfo extends NodeInfo {
+  List<int> lineOffsets;
+
+  UnitInfo(AppInfo appInfo, String path, String content) : super(appInfo, null, 'unit', path) {

[Bob Nystrom, 2013/06/17 21:30:12]

Move ": super..." to the next line.

[scheglov, 2013/06/17 22:30:57]

Done.

+    lineOffsets = getLineOffsets(content);
+  }
+
+  UnitInfo get unit => this;
+
+  int getLine(int offset) {
+    return binarySearch(lineOffsets, (x) => x >= offset);
+  }
+}