Merge pull request #4334 from gzm0/handle-js-optional-default-params

gzm0 · web-flow · commit eba131d08c70 · 2020-12-16T20:34:07.000+01:00
Fix #4322: Handle JSOptional default parameters in JS traits
diff --git a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSExports.scala b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSExports.scala
@@ -767,7 +767,10 @@ trait GenJSExports[G <: Global with Singleton] extends SubComponent {
 
       if (isJSType(trgSym)) {
         if (isNonNativeJSClass(defaultGetter.owner)) {
-          genApplyJSClassMethod(trgTree, defaultGetter, defaultGetterArgs)
+          if (defaultGetter.hasAnnotation(JSOptionalAnnotation))
+            js.Undefined()
+          else
+            genApplyJSClassMethod(trgTree, defaultGetter, defaultGetterArgs)
         } else {
           reporter.error(paramPos, "When overriding a native method " +
               "with default arguments, the overriding method must " +
diff --git a/test-suite/js/src/test/scala/org/scalajs/testsuite/jsinterop/JSOptionalTest.scala b/test-suite/js/src/test/scala/org/scalajs/testsuite/jsinterop/JSOptionalTest.scala
@@ -239,6 +239,23 @@ class JSOptionalTest {
     assertEquals("function", js.typeOf(obj.f))
     assertEquals(6, obj.f.get(5))
   }
+
+  @Test def traitWithOptionalDefaultParameter(): Unit = {
+    object InheritDefault extends TraitWithOptionalDefaultParameter {
+      def foo(x: js.UndefOr[Int]): Int = x.getOrElse(5)
+    }
+
+    assertEquals(5, InheritDefault.foo())
+    assertEquals(10, InheritDefault.foo(10))
+
+    object NewDefault extends TraitWithOptionalDefaultParameter {
+      def foo(x: js.UndefOr[Int] = 6): Int =
+        x.getOrElse(throw new AssertionError("x was js.undefined"))
+    }
+
+    assertEquals(6, NewDefault.foo())
+    assertEquals(10, NewDefault.foo(10))
+  }
 }
 
 object JSOptionalTest {
@@ -303,4 +320,8 @@ object JSOptionalTest {
   trait TraitWithOptionalFunction extends js.Object {
     val f: js.UndefOr[js.Function1[Int, Int]] = js.undefined
   }
+
+  trait TraitWithOptionalDefaultParameter extends js.Object {
+    def foo(x: js.UndefOr[Int] = js.undefined): Int
+  }
 }
