Add microsecond support to DateTime.

sdk/lib/_internal/js_runtime/lib/core_patch.dart

Index: sdk/lib/_internal/js_runtime/lib/core_patch.dart
diff --git a/sdk/lib/_internal/js_runtime/lib/core_patch.dart b/sdk/lib/_internal/js_runtime/lib/core_patch.dart
index 9dd31a4920723f9dbe71d8fb97ee1c43c189daee..7b7b37ca20259068564e2154582fa558f762f0a2 100644
--- a/sdk/lib/_internal/js_runtime/lib/core_patch.dart
+++ b/sdk/lib/_internal/js_runtime/lib/core_patch.dart
@@ -186,6 +186,18 @@ class Error {
 @patch
 class DateTime {
   @patch
+  DateTime.fromMillisecondsSinceEpoch(int millisecondsSinceEpoch,
+                                                  {bool isUtc: false})

[Lasse Reichstein Nielsen, 2015/12/03 09:16:22]

indentation is wrong.

[floitsch, 2015/12/04 08:11:31]

Done.

+      : this._withValue(millisecondsSinceEpoch, isUtc: isUtc);
+
+  @patch
+  DateTime.fromMicrosecondsSinceEpoch(int microsecondsSinceEpoch,
+                                      {bool isUtc: false})
+      : this._withValue(
+          _microsecondInRoundedMilliseconds(microsecondsSinceEpoch),
+          isUtc: isUtc);
+
+  @patch
   DateTime._internal(int year,
                      int month,
                      int day,
@@ -193,26 +205,38 @@ class DateTime {
                      int minute,
                      int second,
                      int millisecond,
+                     int microsecond,
                      bool isUtc)
         // checkBool is manually inlined here because dart2js doesn't inline it
         // and [isUtc] is usually a constant.
       : this.isUtc = isUtc is bool
             ? isUtc
             : throw new ArgumentError.value(isUtc, 'isUtc'),
-        millisecondsSinceEpoch = checkInt(Primitives.valueFromDecomposedDate(
-            year, month, day, hour, minute, second, millisecond, isUtc));
+        _value = checkInt(Primitives.valueFromDecomposedDate(
+            year, month, day, hour, minute, second,
+            millisecond + _microsecondInRoundedMilliseconds(microsecond),
+            isUtc));
 
   @patch
   DateTime._now()
       : isUtc = false,
-        millisecondsSinceEpoch = Primitives.dateNow();
+        _value = Primitives.dateNow();
+
+  /// Rounds the given [microsecond] to the nearest milliseconds value.
+  ///
+  /// For example, invoked with argument `2600` returns `3`.
+  static int _microsecondInRoundedMilliseconds(int microsecond) {
+    return (microsecond / 1000).round();
+  }
 
   @patch
-  static int _brokenDownDateToMillisecondsSinceEpoch(
+  static int _brokenDownDateToValue(
       int year, int month, int day, int hour, int minute, int second,
-      int millisecond, bool isUtc) {
+      int millisecond, int microsecond, bool isUtc) {
     return Primitives.valueFromDecomposedDate(
-        year, month, day, hour, minute, second, millisecond, isUtc);
+        year, month, day, hour, minute, second,
+        millisecond + _microsecondInRoundedMilliseconds(microsecond),
+        isUtc);
   }
 
   @patch
@@ -228,6 +252,29 @@ class DateTime {
   }
 
   @patch
+  DateTime add(Duration duration) {
+    return new DateTime._withValue(
+        _value + duration.inMilliseconds, isUtc: isUtc);

[Lasse Reichstein Nielsen, 2015/12/03 09:16:22]

This means that microseconds are ignored, not rounded like they are in the
constructor. This is now visible.
  
  var now = new DateTime.now();
  var then = now.add(const Duration(microseconds: 1))
  print(now == then);  // True in dart2js, false in VM.

I guess that's the cost of doing business with JS.

[floitsch, 2015/12/04 08:11:31]

Do you want me to round them?
Unless I made a mistake this is the behavior we had before this patch.

[Lasse Reichstein Nielsen, 2015/12/04 08:15:02]

I think it's probably fine.
Before this change, users wouldn't expect DateTime to understand microseconds,
so having them ignored was expected. Now it looks like they are supported, and
Duration does support them, so it's more surprising when they are lost (I don't
think it makes a difference whether we round or truncate).

+  }
+
+  @patch
+  DateTime subtract(Duration duration) {
+    return new DateTime._withValue(
+        _value - duration.inMilliseconds, isUtc: isUtc);
+  }
+
+  @patch
+  Duration difference(DateTime other) {
+    return new Duration(milliseconds: _value - other._value);
+  }
+
+  @patch
+  int get millisecondsSinceEpoch => _value;
+
+  @patch
+  int get microsecondsSinceEpoch => _value * 1000;
+
+  @patch
   int get year => Primitives.getYear(this);
 
   @patch
@@ -249,6 +296,9 @@ class DateTime {
   int get millisecond => Primitives.getMilliseconds(this);
 
   @patch
+  int get microsecond => 0;
+
+  @patch
   int get weekday => Primitives.getWeekday(this);
 }