Merge pull request #5228 from sjrd/better-system-time-impl

sjrd · web-flow · commit b024d1b08a38 · 2025-09-01T13:37:12.000+02:00
Better implementations of System.{currentTimeMillis,nanoTime}.
diff --git a/javalib/src/main/scala/java/lang/System.scala b/javalib/src/main/scala/java/lang/System.scala
@@ -68,29 +68,20 @@ object System {
 
   @inline
   def currentTimeMillis(): scala.Long =
-    (new js.Date).getTime().toLong
+    js.Date.now().toLong
 
   private object NanoTime {
-    val getHighPrecisionTime: js.Function0[scala.Double] = {
-      import js.DynamicImplicits.truthValue
-
-      if (js.typeOf(global.performance) != "undefined") {
-        if (global.performance.now) {
-          () => global.performance.now().asInstanceOf[scala.Double]
-        } else if (global.performance.webkitNow) {
-          () => global.performance.webkitNow().asInstanceOf[scala.Double]
-        } else {
-          () => new js.Date().getTime()
-        }
-      } else {
-        () => new js.Date().getTime()
-      }
+    val highPrecisionTimer: js.Dynamic = {
+      if (js.typeOf(global.performance) != "undefined" && !Utils.isUndefined(global.performance.now))
+        global.performance
+      else
+        global.Date
     }
   }
 
   @inline
   def nanoTime(): scala.Long =
-    (NanoTime.getHighPrecisionTime() * 1000000).toLong
+    (NanoTime.highPrecisionTimer.now().asInstanceOf[scala.Double] * 1000000).toLong
 
   // arraycopy ----------------------------------------------------------------
 
diff --git a/javalib/src/main/scala/java/util/Date.scala b/javalib/src/main/scala/java/util/Date.scala
@@ -23,12 +23,7 @@ class Date(private var millis: Long) extends Object
 
   import Date._
 
-  def this() = {
-    /* No need to check for overflow. If SJS lives that long (~year 275760),
-     * it's OK to have a bug ;-)
-     */
-    this(js.Date.now().toLong)
-  }
+  def this() = this(System.currentTimeMillis())
 
   @Deprecated
   def this(year: Int, month: Int, date: Int, hrs: Int, min: Int, sec: Int) =
diff --git a/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/lang/SystemTest.scala b/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/lang/SystemTest.scala
@@ -53,6 +53,23 @@ class SystemTest {
     }
   }
 
+  @Test def currentTimeMillis(): Unit = {
+    // Test that the "scale" (order of magnitude) of currentTimeMillis() is correct
+    val result = System.currentTimeMillis()
+    assertTrue(result.toString(), result >= 1360059308000L) // timestamp of the first commit of Scala.js
+    assertTrue(result.toString(), result <= 2937896108000L) // 50 years later
+  }
+
+  @Test def nanoTime(): Unit = {
+    /* nanoTime() can return arbitrary results; even negative values.
+     * It is supposed to be monotonic, but apparently it sometimes incorrectly
+     * goes back in time: https://bugs.java.com/bugdatabase/view_bug?bug_id=6458294
+     *
+     * So the only thing we can test is that it links.
+     */
+    System.nanoTime()
+  }
+
   @Test def identityHashCode(): Unit = {
     class HasIDHashCode
 
