Improve precision of JS printer callbacks (2nd try)

pkg/js_ast/test/printer_callback_test.dart

Index: pkg/js_ast/test/printer_callback_test.dart
diff --git a/pkg/js_ast/test/printer_callback_test.dart b/pkg/js_ast/test/printer_callback_test.dart
new file mode 100644
index 0000000000000000000000000000000000000000..1a1db3590dbcd8c18020bd1bb79ceab277d90b32
--- /dev/null
+++ b/pkg/js_ast/test/printer_callback_test.dart
@@ -0,0 +1,161 @@
+// 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.
+
+// Test that JS printer callbacks occur when expected.
+
+library js_ast.printer.callback_test;
+
+import 'package:js_ast/js_ast.dart';
+import 'package:unittest/unittest.dart';
+
+enum TestMode {
+  NONE,
+  ENTER,
+  DELIMITER,
+  EXIT,
+}
+
+const DATA = const [
+  const {
+    TestMode.NONE: """
+function(a, b) {
+  return null;
+}""",
+    TestMode.ENTER: """
+@0function(@1a, @2b) @3{
+  @4return @5null;
+}""",
+    TestMode.DELIMITER: """
+function(a, b) {
+  return null;
+@0}""",
+   TestMode.EXIT: """
+function(a@1, b@2) {
+  return null@5;
+@4}@3@0"""
+  },
+
+  const {
+    TestMode.NONE: """
+function() {
+  if (true) {
+    foo1();
+    foo2();
+  } else {
+    bar1();
+    bar2();
+  }
+  while (false) {
+    baz3();
+    baz4();
+  }
+}""",
+    TestMode.ENTER: """
+@0function() @1{
+  @2if (@3true) @4{
+    @5@6@7foo1();
+    @8@9@10foo2();
+  } else @11{
+    @12@13@14bar1();
+    @15@16@17bar2();
+  }
+  @18while (@19false) @20{
+    @21@22@23baz3();
+    @24@25@26baz4();
+  }
+}""",
+    TestMode.DELIMITER: """
+function() {
+  if (true) {
+    foo1();
+    foo2();
+  } else {
+    bar1();
+    bar2();
+  }
+  while (false) {
+    baz3();
+    baz4();
+  }
+@0}""",
+    TestMode.EXIT: """
+function() {
+  if (true@3) {
+    foo1@7()@6;
+@5    foo2@10()@9;
+@8  }@4 else {
+    bar1@14()@13;
+@12    bar2@17()@16;
+@15  }@11
+@2  while (false@19) {
+    baz3@23()@22;
+@21    baz4@26()@25;
+@24  }@20
+@18}@1@0""",
+  },
+];
+
+void check(Map<TestMode, String> map) {
+  String code = map[TestMode.NONE];
+  JavaScriptPrintingOptions options = new JavaScriptPrintingOptions();
+  Node node = js.parseForeignJS(code).instantiate({});
+  map.forEach((TestMode mode, String expectedOutput) {
+    Context context = new Context(mode);
+    new Printer(options, context).visit(node);
+    expect(context.getText(), equals(expectedOutput),
+        reason: "Unexpected output for $code in $mode");
+  });
+}
+
+class Context extends SimpleJavaScriptPrintingContext {
+  final TestMode mode;
+  final Map<Node, int> idMap = {};
+  final Map<int, List<String>> tagMap = {};
+
+  Context(this.mode);
+
+  int id(Node node) => idMap.putIfAbsent(node, () => idMap.length);
+
+  String tag(int value) => '@$value';
+
+  void enterNode(Node node, int startPosition) {
+    int value = id(node);
+    if (mode == TestMode.ENTER) {
+      tagMap.putIfAbsent(startPosition, () => []).add(tag(value));
+    }
+  }
+
+  void exitNode(Node node,
+                int startPosition,
+                int endPosition,
+                int delimiterPosition) {
+    int value = id(node);
+    if (mode == TestMode.DELIMITER && delimiterPosition != null) {
+      tagMap.putIfAbsent(delimiterPosition, () => []).add(tag(value));
+    } else if (mode == TestMode.EXIT) {
+      tagMap.putIfAbsent(endPosition, () => []).add(tag(value));
+    }
+  }
+
+  String getText() {
+    String text = super.getText();
+    int offset = 0;
+    StringBuffer sb = new StringBuffer();
+    for (int position in tagMap.keys.toList()..sort()) {
+      if (offset < position) {
+        sb.write(text.substring(offset, position));
+      }
+      tagMap[position].forEach((String tag) => sb.write(tag));
+      offset = position;
+    }
+    if (offset < text.length) {
+      sb.write(text.substring(offset));
+    }
+    return sb.toString();
+  }
+}
+
+void main() {
+  DATA.forEach(check);
+}