Change the toString method of IterableBase/IterableMixin to show some elements.

tests/corelib/iterable_tostring_test.dart

Index: tests/corelib/iterable_tostring_test.dart
diff --git a/tests/corelib/iterable_tostring_test.dart b/tests/corelib/iterable_tostring_test.dart
new file mode 100644
index 0000000000000000000000000000000000000000..ee93170c3d329c8efb9c0d7f64344e61068d5fc1
--- /dev/null
+++ b/tests/corelib/iterable_tostring_test.dart
@@ -0,0 +1,106 @@
+// 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.
+
+// Test the IterableBase/IterableMixin toString method.
+
+import "package:expect/expect.dart";
+import "dart:collection";
+
+String mkIt(int len, [func]) {
+  var list;
+  if (func == null) {
+    list = new List.generate(len, (x) => x);
+  } else {
+    list = new List.generate(len, func);
+  }
+  return new MyIterable(list).toString();
+}
+
+class MyIterable extends IterableBase {
+  final Iterable _base;
+  MyIterable(this._base);
+  Iterator get iterator => _base.iterator;
+}
+
+void main() {
+  Expect.equals("()", mkIt(0));
+  Expect.equals("(0)", mkIt(1));
+  Expect.equals("(0, 1)", mkIt(2));
+  Expect.equals("(0, 1, 2, 3, 4, 5, 6, 7, 8)", mkIt(9));
+
+  // Builds string up to 60 characters, then finishes with last two
+  // elements.
+  Expect.equals(
+     //0123456789012345678901234567890123456789 - 40 characters
+      "(0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 1"
+      "2, 13, 14, 15, 16, 17, 18, ..., 98, 99)",
+      mkIt(100));
+
+  Expect.equals(
+     //0123456789012345678901234567890123456789
+      "(0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 1"
+      "2, 13, 14, 15, 16, 17, 18)",
+      mkIt(19));
+
+  Expect.equals(
+     //0123456789012345678901234567890123456789
+      "(0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 1"
+      "2, 13, 14, 15, 16, 17, 18, 19)",
+      mkIt(20));
+
+  Expect.equals(
+     //0123456789012345678901234567890123456789
+      "(0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 1"
+      "2, 13, 14, 15, 16, 17, 18, 19, 20)",
+      mkIt(21));
+
+  // Don't show last two elements if more than 100 elements total
+  // (can't be 100 elements in 80 characters including commas).
+  Expect.equals(
+     //0123456789012345678901234567890123456789
+      "(0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 1"
+      "2, 13, 14, 15, 16, 17, 18, 19, 20, ...)",
+      mkIt(101));
+
+  // If last two elements bring total over 80 characters, drop some of
+  // the previous ones as well.
+
+  Expect.equals(
+     //0123456789012345678901234567890123456789
+      "(0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 1"
+      "2, 13, ..., 18, xxxxxxxxxxxxxxxxxxxx)",
+      mkIt(20, (x) => x == 19 ? "xxxxxxxxxxxxxxxxxxxx": "$x"));
+
+  // Never drop the first three or the last two.
+  Expect.equals(
+     //0123456789012345678901234567890123456789
+      "(xxxxxxxxxxxxxxxxx, xxxxxxxxxxxxxxxxx, x"
+      "xxxxxxxxxxxxxxxx, ..., 18, xxxxxxxxxxxxx"
+      "xxxx)",
+      mkIt(20, (x) => (x < 3 || x == 19) ? "xxxxxxxxxxxxxxxxx": "$x"));
+
+  // Never drop the first three or the last two.
+  Expect.equals(
+     //0123456789012345678901234567890123456789
+      "(xxxxxxxxxxxxxxxxx, xxxxxxxxxxxxxxxxx, x"
+      "xxxxxxxxxxxxxxxx, ..., xxxxxxxxxxxxxxxxx"
+      ", 19)",
+      mkIt(20, (x) => (x < 3 || x == 18) ? "xxxxxxxxxxxxxxxxx": "$x"));
+
+  // If the first three are very long, always include them anyway.
+  Expect.equals(
+     //0123456789012345678901234567890123456789
+      "(xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx,"
+      " xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx,"
+      " xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx,"
+      " ..., 98, 99)",
+      mkIt(100, (x) =>
+                    (x < 3 ) ? "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx": "$x"));
+
+  Expect.equals(
+     //0123456789012345678901234567890123456789
+      "(, , , , , , , , , , , , , , , , , , , ,"
+      " , , , , , , , , , , , , , , , ..., , )",
+      mkIt(100, (_) => ""));
+}