Fix DCHECK in AXPlatformNodeTextRangeProviderWin::NormalizeTextRange

With Narrator and UIA enabled if the user navigates to the end of a
document, then the document is modified such that Narrator now has a
range whos |start_| or |end_| position is at the end or start of the
document respectively, |NormalizeTextRange| would have created a
NULL_POSITION for that range edge.

To avoid this, if there is no next/previous character for that edge
of the range, then that edge position will not be modified.

Bug: 1015593
Change-Id: If706057eaf533dfd0ab5e544eefd102d95ca767e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1869716Reviewed-by: Kurt Catti-Schmidt <kschmi@microsoft.com>
Commit-Queue: Adam Ettenberger <adettenb@microsoft.com>
Cr-Commit-Position: refs/heads/master@{#707573}

ui/accessibility/platform/ax_platform_node_textrangeprovider_win.cc

@@ -1015,12 +1015,16 @@ void AXPlatformNodeTextRangeProviderWin::NormalizeTextRange() {
   // Only normalize non-degenerate ranges.
   if (*start_ != *end_) {
     AXPositionInstance normalized_start = start_->AsPositionBeforeCharacter();
-    AXPositionInstance normalized_end = end_->AsPositionAfterCharacter();
-    DCHECK_EQ(*start_, *normalized_start);
-    DCHECK_EQ(*end_, *normalized_end);
+    if (!normalized_start->IsNullPosition()) {
+      DCHECK_EQ(*start_, *normalized_start);
+      start_ = std::move(normalized_start);
+    }
 
-    start_ = std::move(normalized_start);
-    end_ = std::move(normalized_end);
+    AXPositionInstance normalized_end = end_->AsPositionAfterCharacter();
+    if (!normalized_end->IsNullPosition()) {
+      DCHECK_EQ(*end_, *normalized_end);
+      end_ = std::move(normalized_end);
+    }
   }
 }
 

ui/accessibility/platform/ax_platform_node_textrangeprovider_win_unittest.cc

@@ -196,6 +196,10 @@ class AXPlatformNodeTextRangeProviderTest : public ui::AXPlatformNodeWinTest {
     return text_range->owner_;
   }
 
+  void NormalizeTextRange(AXPlatformNodeTextRangeProviderWin* text_range) {
+    text_range->NormalizeTextRange();
+  }
+
   void GetTextRangeProviderFromTextNode(
       ComPtr<ITextRangeProvider>& text_range_provider,
       ui::AXNode* text_node) {
@@ -4501,4 +4505,118 @@ TEST_F(AXPlatformNodeTextRangeProviderTest,
       /*expected_count*/ 12);
 }
 
+TEST_F(AXPlatformNodeTextRangeProviderTest,
+       TestNormalizeTextRangePastEndOfDocument) {
+  ui::AXTreeUpdate initial_state;
+  ui::AXTreeID tree_id = ui::AXTreeID::CreateNewAXTreeID();
+  initial_state.tree_data.tree_id = tree_id;
+  initial_state.has_tree_data = true;
+  initial_state.root_id = 1;
+  initial_state.nodes.resize(3);
+  initial_state.nodes[0].id = 1;
+  initial_state.nodes[0].child_ids = {2};
+  initial_state.nodes[0].role = ax::mojom::Role::kRootWebArea;
+  initial_state.nodes[1].id = 2;
+  initial_state.nodes[1].child_ids = {3};
+  initial_state.nodes[1].role = ax::mojom::Role::kStaticText;
+  initial_state.nodes[1].SetName("aaa");
+  initial_state.nodes[2].id = 3;
+  initial_state.nodes[2].role = ax::mojom::Role::kInlineTextBox;
+  initial_state.nodes[2].SetName("aaa");
+
+  Init(initial_state);
+  AXNodePosition::SetTree(tree_.get());
+
+  ComPtr<ITextRangeProvider> text_range_provider;
+  GetTextRangeProviderFromTextNode(text_range_provider,
+                                   GetNodeFromTree(tree_id, 3));
+
+  EXPECT_UIA_TEXTRANGE_EQ(text_range_provider, L"aaa");
+  EXPECT_UIA_MOVE_ENDPOINT_BY_UNIT(
+      text_range_provider, TextPatternRangeEndpoint_Start, TextUnit_Character,
+      /*count*/ 2,
+      /*expected_text*/ L"a",
+      /*expected_count*/ 2);
+
+  ComPtr<AXPlatformNodeTextRangeProviderWin> text_range_provider_win;
+  text_range_provider->QueryInterface(IID_PPV_ARGS(&text_range_provider_win));
+
+  const AXNodePosition::AXPositionInstance start_after_move =
+      GetStart(text_range_provider_win.Get())->Clone();
+  const AXNodePosition::AXPositionInstance end_after_move =
+      GetEnd(text_range_provider_win.Get())->Clone();
+  EXPECT_LT(*start_after_move, *end_after_move);
+
+  AXTreeUpdate update;
+  update.nodes.resize(2);
+  update.nodes[0] = initial_state.nodes[1];
+  update.nodes[0].SetName("aa");
+  update.nodes[1] = initial_state.nodes[2];
+  update.nodes[1].SetName("aa");
+  ASSERT_TRUE(tree_->Unserialize(update));
+
+  NormalizeTextRange(text_range_provider_win.Get());
+  EXPECT_EQ(*start_after_move, *GetStart(text_range_provider_win.Get()));
+  EXPECT_EQ(*end_after_move, *GetEnd(text_range_provider_win.Get()));
+}
+
+TEST_F(AXPlatformNodeTextRangeProviderTest,
+       TestNormalizeTextRangePastEndOfDocumentWithIgnoredNodes) {
+  ui::AXTreeUpdate initial_state;
+  ui::AXTreeID tree_id = ui::AXTreeID::CreateNewAXTreeID();
+  initial_state.tree_data.tree_id = tree_id;
+  initial_state.has_tree_data = true;
+  initial_state.root_id = 1;
+  initial_state.nodes.resize(4);
+  initial_state.nodes[0].id = 1;
+  initial_state.nodes[0].child_ids = {2};
+  initial_state.nodes[0].role = ax::mojom::Role::kRootWebArea;
+  initial_state.nodes[1].id = 2;
+  initial_state.nodes[1].child_ids = {3, 4};
+  initial_state.nodes[1].role = ax::mojom::Role::kStaticText;
+  initial_state.nodes[1].SetName("aaa");
+  initial_state.nodes[2].id = 3;
+  initial_state.nodes[2].role = ax::mojom::Role::kInlineTextBox;
+  initial_state.nodes[2].SetName("aaa");
+  initial_state.nodes[3].id = 4;
+  initial_state.nodes[3].role = ax::mojom::Role::kInlineTextBox;
+  initial_state.nodes[3].AddState(ax::mojom::State::kIgnored);
+  initial_state.nodes[3].SetName("ignored");
+
+  Init(initial_state);
+  AXNodePosition::SetTree(tree_.get());
+
+  ComPtr<ITextRangeProvider> text_range_provider;
+  GetTextRangeProviderFromTextNode(text_range_provider,
+                                   GetNodeFromTree(tree_id, 3));
+
+  EXPECT_UIA_TEXTRANGE_EQ(text_range_provider, L"aaa");
+  EXPECT_UIA_MOVE_ENDPOINT_BY_UNIT(
+      text_range_provider, TextPatternRangeEndpoint_Start, TextUnit_Character,
+      /*count*/ 2,
+      /*expected_text*/ L"a",
+      /*expected_count*/ 2);
+
+  ComPtr<AXPlatformNodeTextRangeProviderWin> text_range_provider_win;
+  text_range_provider->QueryInterface(IID_PPV_ARGS(&text_range_provider_win));
+
+  const AXNodePosition::AXPositionInstance start_after_move =
+      GetStart(text_range_provider_win.Get())->Clone();
+  const AXNodePosition::AXPositionInstance end_after_move =
+      GetEnd(text_range_provider_win.Get())->Clone();
+  EXPECT_LT(*start_after_move, *end_after_move);
+
+  AXTreeUpdate update;
+  update.nodes.resize(2);
+  update.nodes[0] = initial_state.nodes[1];
+  update.nodes[0].SetName("aa");
+  update.nodes[1] = initial_state.nodes[2];
+  update.nodes[1].SetName("aa");
+  ASSERT_TRUE(tree_->Unserialize(update));
+
+  NormalizeTextRange(text_range_provider_win.Get());
+  EXPECT_EQ(*start_after_move, *GetStart(text_range_provider_win.Get()));
+  EXPECT_EQ(*end_after_move, *GetEnd(text_range_provider_win.Get()));
+}
+
 }  // namespace ui