Re-land: Fix accessibility dump tree tests to not need an end-of-file sentinel.

Original: http://crrev.com/c/2109458
Reverted: http://crrev.com/c/2111771

This change depended on fixing all of the -expected*.txt files in
content/test/data/accessibility, but another one landed before this
one.

The DumpAccessibilityTree tests generate an output text file and diff
the results against an expected file. Previously, the way that the
algorithm handled files of different lengths was by adding an
end-of-file sentinel to the end. This resulted in that sentinel
getting checked in, which was just confusing.

Fix this by modifying the DiffLines helper function to properly compare
files that don't have the same number of lines. Add full unit tests for
DiffLines so we can be confident it works.

Continue to LOG the end-of-file sentinel, because it's needed by
running rebase_dump_accessibility_tree_test.py to parse actual output
files from remote logs.

Bug: 1063167
Tbr: aleventhal@chromium.org
Change-Id: I6c52bc77c3e4bb6e07d77971a5d748d9bf0d1f75
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2112116Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
Commit-Queue: Dominic Mazzoni <dmazzoni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#751945}

chrome/test/data/pdf/accessibility/whitespace-expected.txt

- 

content/browser/accessibility/dump_accessibility_browsertest_base.cc

@@ -367,7 +367,6 @@ void DumpAccessibilityTestBase::RunTestForPlatform(
   }
 
   // Validate against the expectation file.
-  actual_lines.push_back(kMarkEndOfFile);
   bool matches_expectation = test_helper.ValidateAgainstExpectation(
       file_path, expected_file, actual_lines, *expected_lines);
   EXPECT_TRUE(matches_expectation);

content/public/test/dump_accessibility_test_helper.cc

@@ -19,9 +19,8 @@ namespace {
 const char kCommentToken = '#';
 const char kMarkSkipFile[] = "#<skip";
 const char kSignalDiff[] = "*";
-}  // namespace
-
 const char kMarkEndOfFile[] = "<-- End-of-file -->";
+}  // namespace
 
 DumpAccessibilityTestHelper::DumpAccessibilityTestHelper(
     AccessibilityTestExpectationsLocator* test_locator)
@@ -80,10 +79,6 @@ DumpAccessibilityTestHelper::LoadExpectationFile(
       base::SplitString(expected_contents, "\n", base::KEEP_WHITESPACE,
                         base::SPLIT_WANT_NONEMPTY);
 
-  // Marking the end of the file with a line of text ensures that
-  // file length differences are found.
-  expected_lines.push_back(kMarkEndOfFile);
-
   return expected_lines;
 }
 
@@ -123,6 +118,11 @@ bool DumpAccessibilityTestHelper::ValidateAgainstExpectation(
     diff += "------\n";
     diff += base::JoinString(actual_lines, "\n");
     diff += "\n";
+
+    // This is used by rebase_dump_accessibility_tree_test.py to signify
+    // the end of the file when parsing the actual output from remote logs.
+    diff += kMarkEndOfFile;
+    diff += "\n";
     LOG(ERROR) << "Diff:\n" << diff;
   } else {
     LOG(INFO) << "Test output matches expectations.";
@@ -163,6 +163,20 @@ std::vector<int> DumpAccessibilityTestHelper::DiffLines(
     ++j;
   }
 
+  // Report a failure if there are additional expected lines or
+  // actual lines.
+  if (i < actual_lines_count) {
+    diff_lines.push_back(j);
+  } else {
+    while (j < expected_lines_count) {
+      if (expected_lines[j].size() > 0 &&
+          expected_lines[j][0] != kCommentToken) {
+        diff_lines.push_back(j);
+      }
+      j++;
+    }
+  }
+
   // Actual file has been fully checked.
   return diff_lines;
 }

content/public/test/dump_accessibility_test_helper.h

@@ -5,6 +5,7 @@
 #ifndef CONTENT_PUBLIC_TEST_DUMP_ACCESSIBILITY_TEST_HELPER_H_
 #define CONTENT_PUBLIC_TEST_DUMP_ACCESSIBILITY_TEST_HELPER_H_
 
+#include "base/gtest_prod_util.h"
 #include "base/optional.h"
 
 namespace base {
@@ -13,9 +14,6 @@ class FilePath;
 
 namespace content {
 
-// Sentinal value to mark end of actual/expected results.
-extern const char kMarkEndOfFile[];
-
 class AccessibilityTestExpectationsLocator;
 
 // A helper class for writing accessibility tree dump tests.
@@ -46,6 +44,8 @@ class DumpAccessibilityTestHelper {
       const std::vector<std::string>& expected_lines);
 
  private:
+  FRIEND_TEST_ALL_PREFIXES(DumpAccessibilityTestHelperTest, TestDiffLines);
+
   // Utility helper that does a comment-aware equality check.
   // Returns array of lines from expected file which are different.
   static std::vector<int> DiffLines(

content/public/test/dump_accessibility_test_helper_unittest.cc

+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "content/public/test/dump_accessibility_test_helper.h"
+
+#include "testing/gmock/include/gmock/gmock.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+using testing::ElementsAre;
+
+namespace content {
+
+TEST(DumpAccessibilityTestHelperTest, TestDiffLines) {
+  // Files with the same lines should have an empty diff.
+  EXPECT_THAT(DumpAccessibilityTestHelper::DiffLines({"broccoli", "turnip"},
+                                                     {"broccoli", "turnip"}),
+              ElementsAre());
+
+  // Empty files should have an empty diff.
+  EXPECT_THAT(DumpAccessibilityTestHelper::DiffLines({}, {}), ElementsAre());
+
+  // If one line differs, that line number should be returned as the diff.
+  EXPECT_THAT(DumpAccessibilityTestHelper::DiffLines({"broccoli", "turnip"},
+                                                     {"watermelon", "turnip"}),
+              ElementsAre(0));
+
+  EXPECT_THAT(DumpAccessibilityTestHelper::DiffLines({"broccoli", "turnip"},
+                                                     {"broccoli", "rutabaga"}),
+              ElementsAre(1));
+
+  // Multiple lines can differ.
+  EXPECT_THAT(DumpAccessibilityTestHelper::DiffLines(
+                  {"broccoli", "turnip", "carrot", "squash"},
+                  {"broccoli", "aspartame", "carrot", "toothbrush"}),
+              ElementsAre(1, 3));
+
+  // Blank lines in the expected file are allowed.
+  EXPECT_THAT(DumpAccessibilityTestHelper::DiffLines(
+                  {"", "broccoli", "turnip", "carrot", "", "squash"},
+                  {"broccoli", "turnip", "carrot", "squash"}),
+              ElementsAre());
+
+  // Comments in the expected file are allowed.
+  EXPECT_THAT(
+      DumpAccessibilityTestHelper::DiffLines(
+          {"#Vegetables:", "broccoli", "turnip", "carrot", "", "squash"},
+          {"broccoli", "turnip", "carrot", "squash"}),
+      ElementsAre());
+
+  // Comments or blank lines in the actual file are NOT allowed, that's a diff.
+  EXPECT_THAT(
+      DumpAccessibilityTestHelper::DiffLines(
+          {"broccoli", "turnip", "carrot", "squash"},
+          {"#vegetables", "broccoli", "turnip", "carrot", "", "squash"}),
+      ElementsAre(0, 1, 2, 3, 4));
+
+  // If the expected file has an extra line, that's a diff.
+  EXPECT_THAT(DumpAccessibilityTestHelper::DiffLines(
+                  {"broccoli", "turnip", "cow"}, {"broccoli", "turnip"}),
+              ElementsAre(2));
+
+  // If the actual file has an extra line, that's a diff.
+  EXPECT_THAT(DumpAccessibilityTestHelper::DiffLines(
+                  {"broccoli", "turnip"}, {"broccoli", "turnip", "horse"}),
+              ElementsAre(2));
+
+  // If the expected file has an extra blank line, that's okay.
+  EXPECT_THAT(DumpAccessibilityTestHelper::DiffLines({"broccoli", "turnip", ""},
+                                                     {"broccoli", "turnip"}),
+              ElementsAre());
+}
+
+}  // namespace content

content/test/BUILD.gn

@@ -1916,6 +1916,7 @@ test("content_unittests") {
     "../public/common/url_utils_unittest.cc",
     "../public/test/browser_task_environment_unittest.cc",
     "../public/test/devtools_permission_overrides_unittest.cc",
+    "../public/test/dump_accessibility_test_helper_unittest.cc",
     "../public/test/no_renderer_crashes_assertion_unittest.cc",
     "../public/test/permission_type_unittest.cc",
     "../public/test/referrer_unittest.cc",

content/test/data/accessibility/event/aria-combo-box-collapse-expected-uia-win7.txt

@@ -3,4 +3,3 @@ AutomationFocusChanged on role=combobox
 AutomationFocusChanged on role=combobox
 AutomationFocusChanged on role=option, name=Orange
 ExpandCollapseExpandCollapseState changed on role=combobox
-<-- End-of-file -->

content/test/data/accessibility/event/aria-combo-box-expand-expected-uia-win7.txt

@@ -5,4 +5,3 @@ AutomationFocusChanged on role=option, name=Apple
 AutomationFocusChanged on role=option, name=Apple
 ExpandCollapseExpandCollapseState changed on role=combobox
 SelectionItem_ElementSelected on role=option, name=Apple
-<-- End-of-file -->

content/test/data/accessibility/event/aria-combo-box-next-expected-uia-win7.txt

@@ -11,4 +11,3 @@ AutomationFocusChanged on role=option, name=Banana
 AutomationFocusChanged on role=option, name=Banana
 AutomationFocusChanged on role=option, name=Orange
 SelectionItem_ElementSelected on role=option, name=Banana
-<-- End-of-file -->

content/test/data/accessibility/event/listbox-next-expected-uia-win7.txt

@@ -4,4 +4,3 @@ AutomationFocusChanged on role=option, name=Apple
 AutomationFocusChanged on role=option, name=Orange
 AutomationFocusChanged on role=option, name=Orange
 SelectionItem_ElementSelected on role=option, name=Orange
-<-- End-of-file -->

content/test/data/accessibility/event/menulist-collapse-expected-mac.txt

@@ -2,4 +2,3 @@ AXFocusedUIElementChanged on AXPopUpButton AXValue="Apple"
 === Start Continuation ===
 AXSelectedChildrenChanged on AXMenu
 AXValueChanged on AXPopUpButton
-<-- End-of-file -->

content/test/data/accessibility/event/menulist-collapse-expected-uia-win.txt

@@ -4,4 +4,3 @@ AutomationFocusChanged on role=combobox
 AriaProperties changed on role=listitem, name=Apple
 SelectionItem_ElementRemovedFromSelection on role=listitem, name=Apple
 ValueValue changed on role=combobox
-<-- End-of-file -->

content/test/data/accessibility/event/menulist-collapse-expected-uia-win7.txt

@@ -5,4 +5,3 @@ AriaProperties changed on role=listitem, name=Apple
 AutomationFocusChanged on role=combobox
 SelectionItem_ElementRemovedFromSelection on role=listitem, name=Apple
 ValueValue changed on role=combobox
-<-- End-of-file -->

content/test/data/accessibility/event/menulist-collapse-expected-win.txt

@@ -4,4 +4,3 @@ EVENT_OBJECT_SELECTIONREMOVE on <option> role=ROLE_SYSTEM_LISTITEM name="Apple"
 EVENT_OBJECT_SELECTIONWITHIN on role=ROLE_SYSTEM_LIST INVISIBLE SetSize=3
 EVENT_OBJECT_STATECHANGE on <option> role=ROLE_SYSTEM_LISTITEM name="Apple" INVISIBLE,FOCUSABLE,SELECTABLE PosInSet=1 SetSize=3
 EVENT_OBJECT_VALUECHANGE on <select> role=ROLE_SYSTEM_COMBOBOX FOCUSED,COLLAPSED,FOCUSABLE,HASPOPUP SetSize=3
-<-- End-of-file -->

content/test/data/accessibility/event/menulist-collapse-next-expected-auralinux.txt

@@ -5,4 +5,3 @@ STATE-CHANGE:FOCUSED:TRUE role=ROLE_COMBO_BOX name='(null)' ENABLED,EXPANDABLE,F
 === Start Continuation ===
 SELECTION-CHANGED role=ROLE_MENU name='(null)' ENABLED,SENSITIVE
 STATE-CHANGE:SELECTED:TRUE role=ROLE_MENU_ITEM name='Orange' ENABLED,FOCUSABLE,SELECTABLE,SELECTED,SENSITIVE,SHOWING,VISIBLE
-<-- End-of-file -->
\ No newline at end of file

content/test/data/accessibility/event/menulist-collapse-next-expected-mac.txt

@@ -2,4 +2,3 @@ AXFocusedUIElementChanged on AXPopUpButton AXValue="Apple"
 === Start Continuation ===
 AXSelectedChildrenChanged on AXMenu
 AXValueChanged on AXPopUpButton AXValue="Orange"
-<-- End-of-file -->
\ No newline at end of file

content/test/data/accessibility/event/menulist-collapse-next-expected-uia-win.txt

@@ -5,4 +5,3 @@ AriaProperties changed on role=listitem, name=Apple
 AriaProperties changed on role=listitem, name=Orange
 SelectionItem_ElementSelected on role=listitem, name=Orange
 ValueValue changed on role=combobox
-<-- End-of-file -->

content/test/data/accessibility/event/menulist-collapse-next-expected-uia-win7.txt

@@ -6,4 +6,3 @@ AriaProperties changed on role=listitem, name=Orange
 AutomationFocusChanged on role=combobox
 SelectionItem_ElementSelected on role=listitem, name=Orange
 ValueValue changed on role=combobox
-<-- End-of-file -->

content/test/data/accessibility/event/menulist-collapse-next-expected-win.txt

@@ -5,4 +5,3 @@ EVENT_OBJECT_SELECTIONWITHIN on role=ROLE_SYSTEM_LIST INVISIBLE SetSize=3
 EVENT_OBJECT_STATECHANGE on <option> role=ROLE_SYSTEM_LISTITEM name="Apple" INVISIBLE,FOCUSABLE,SELECTABLE PosInSet=1 SetSize=3
 EVENT_OBJECT_STATECHANGE on <option> role=ROLE_SYSTEM_LISTITEM name="Orange" SELECTED,FOCUSABLE,SELECTABLE PosInSet=2 SetSize=3
 EVENT_OBJECT_VALUECHANGE on <select> role=ROLE_SYSTEM_COMBOBOX value="Orange" FOCUSED,COLLAPSED,FOCUSABLE,HASPOPUP SetSize=3
-<-- End-of-file -->