Bug 1645447 - Add ForwardIterator::Remove and EndLimitedIterator::Remove functions. r=froydnj

Differential Revision: https://phabricator.services.mozilla.com/D79512

xpcom/ds/nsTObserverArray.h

@@ -332,6 +332,13 @@ class nsAutoTObserverArray : protected nsTObserverArray_base {
       NS_ASSERTION(HasMore(), "iterating beyond end of array");
       return base_type::mArray.Elements()[base_type::mPosition++];
     }
+
+    // Removes the element at the current iterator position.
+    // (the last element returned from |GetNext()|)
+    // This will not affect the next call to |GetNext()|
+    void Remove() {
+      return base_type::mArray.RemoveElementAt(base_type::mPosition - 1);
+    }
   };
 
   // EndLimitedIterator works like ForwardIterator, but will not iterate new
@@ -357,6 +364,13 @@ class nsAutoTObserverArray : protected nsTObserverArray_base {
       return base_type::mArray.Elements()[base_type::mPosition++];
     }
 
+    // Removes the element at the current iterator position.
+    // (the last element returned from |GetNext()|)
+    // This will not affect the next call to |GetNext()|
+    void Remove() {
+      return base_type::mArray.RemoveElementAt(base_type::mPosition - 1);
+    }
+
    private:
     ForwardIterator mEnd;
   };

xpcom/tests/gtest/TestObserverArray.cpp

@@ -30,6 +30,7 @@ typedef nsTObserverArray<int> IntArray;
         << "During test " << testNum << ", iterator finished too early"; \
   } while (0)
 
+// XXX Split this up into independent test cases
 TEST(ObserverArray, Tests)
 {
   IntArray arr;
@@ -156,6 +157,24 @@ TEST(ObserverArray, Tests)
    */
 }
 
+TEST(ObserverArray, ForwardIterator_Remove)
+{
+  static const int expected[] = {3, 4};
+
+  IntArray arr;
+  arr.AppendElement(3);
+  arr.AppendElement(4);
+
+  size_t count = 0;
+  for (auto iter = IntArray::ForwardIterator{arr}; iter.HasMore();) {
+    const int next = iter.GetNext();
+    iter.Remove();
+
+    ASSERT_EQ(expected[count++], next);
+  }
+  ASSERT_EQ(2u, count);
+}
+
 TEST(ObserverArray, RangeBasedFor_Value_Forward_NonEmpty)
 {
   IntArray arr;
@@ -550,3 +569,5 @@ TEST(ObserverArray, RangeBasedFor_Reference_NonObserving_NonEmpty)
   EXPECT_EQ(2u, iterations);
   EXPECT_EQ(7, sum);
 }
+
+// TODO add tests for EndLimitedIterator