Bug 1731005 - HTMLEditor::GetActiveEditingHost() does not return editing host if selection is collapsed in `<input>` r=m_kato

If we flush pending notifications before calling `execCommand` in
`insert-*-in-void-element.tentative.html`, `HTMLEditor` does not work because
`GetActiveEditingHost()` returns `nullptr`.  This is wrong because `Selection`
cannot cross native anonymous subtree boundaries and the selection collapsed in
`<input>` element is valid.  Therefore, it should not check whether the content
has independent selection or not.

Differential Revision: https://phabricator.services.mozilla.com/D125791

editor/libeditor/HTMLEditor.cpp

@@ -5845,12 +5845,14 @@ Element* HTMLEditor::GetActiveEditingHost(
   }
   nsIContent* content = focusNode->AsContent();
 
-  // If the active content isn't editable, or it has independent selection,
-  // we're not active.
-  if (!content->HasFlag(NODE_IS_EDITABLE) ||
-      content->HasIndependentSelection()) {
+  // If the active content isn't editable, we're not active.
+  if (!content->HasFlag(NODE_IS_EDITABLE)) {
     return nullptr;
   }
+  // Note that `Selection` shouldn't be in the native anonymous subtree of
+  // <input>/<textarea>, but can be in them (e.g., collapsed at {<input> - 0}).
+  // Even in such case, we need to look for an ancestor which does not have
+  // editable parent.
   Element* candidateEditingHost = content->GetEditingHost();
   if (!candidateEditingHost) {
     return nullptr;

testing/web-platform/meta/editing/other/insert-paragraph-in-void-element.tentative.html.ini

@@ -2,6 +2,9 @@
   [Inserting paragraph when selection is collapsed in <hr> in <div> which is only child]
     expected: FAIL
 
+  [Inserting paragraph when selection is collapsed in <hr> in <div> which is only child (explicitly flushes maybe pending layout)]
+    expected: FAIL
+
   [Inserting paragraph when selection is collapsed in <hr> which follows a text node in <div>]
     expected: FAIL
 
@@ -11,12 +14,18 @@
   [Inserting paragraph when selection is collapsed in <embed> in <h1> which is only child]
     expected: FAIL
 
+  [Inserting paragraph when selection is collapsed in <embed> in <h1> which is only child (explicitly flushes maybe pending layout)]
+    expected: FAIL
+
   [Inserting paragraph when selection is collapsed in <embed> which follows a text node in <h1>]
     expected: FAIL
 
   [Inserting paragraph when selection is collapsed in <hr> in <h1> which is only child]
     expected: FAIL
 
+  [Inserting paragraph when selection is collapsed in <hr> in <h1> which is only child (explicitly flushes maybe pending layout)]
+    expected: FAIL
+
   [Inserting paragraph when selection is collapsed in <hr> which follows a text node in <h1>]
     expected: FAIL
 
@@ -26,15 +35,24 @@
   [Inserting paragraph when selection is collapsed in <wbr> in <h1> which is only child]
     expected: FAIL
 
+  [Inserting paragraph when selection is collapsed in <wbr> in <h1> which is only child (explicitly flushes maybe pending layout)]
+    expected: FAIL
+
   [Inserting paragraph when selection is collapsed in <wbr> which follows a text node in <h1>]
     expected: FAIL
 
   [Inserting paragraph when selection is collapsed in <br> in <li> which is only child]
     expected: FAIL
 
+  [Inserting paragraph when selection is collapsed in <br> in <li> which is only child (explicitly flushes maybe pending layout)]
+    expected: FAIL
+
   [Inserting paragraph when selection is collapsed in <hr> in <li> which is only child]
     expected: FAIL
 
+  [Inserting paragraph when selection is collapsed in <hr> in <li> which is only child (explicitly flushes maybe pending layout)]
+    expected: FAIL
+
   [Inserting paragraph when selection is collapsed in <hr> which follows a text node in <li>]
     expected: FAIL
 

testing/web-platform/tests/editing/other/insert-paragraph-in-void-element.tentative.html

@@ -89,6 +89,49 @@ for (const container of ["div", "h1", "li"]) {
       }
     }, `Inserting paragraph when selection is collapsed in <${tag}> in <${container}> which is only child`);
 
+    test(() => {
+      editor.innerHTML = `${openTagOfContainer}<${tag}>${closeTagOfContainer}`;
+      const element = editor.querySelector(tag);
+      editor.focus();
+      const selection = getSelection();
+      selection.collapse(element, 0);
+      element.getBoundingClientRect();
+      document.execCommand("insertParagraph");
+      if (tag == "br") {
+        if (!visibleTag && container == "h1") {
+          assert_in_array(
+            editor.innerHTML,
+            `${openTagOfContainer}<br>${closeTagOfContainer}<div><br></div>`,
+            `The paragraph should be inserted before the <${tag}> element`
+          );
+        } else {
+          assert_in_array(
+            editor.innerHTML,
+            `${openTagOfContainer}<br>${closeAndOpenTagsOfSplitPoint}<br>${closeTagOfContainer}`,
+            `The paragraph should be inserted before the <${tag}> element`
+          );
+        }
+      } else if (!visibleTag && container == "h1") {
+        assert_in_array(
+          editor.innerHTML,
+          [
+            `${openTagOfContainer}<br>${closeTagOfContainer}<div><${tag}></div>`,
+            `${openTagOfContainer}<br>${closeTagOfContainer}<div><${tag}><br></div>`,
+          ],
+          `The paragraph should be inserted before the <${tag}> element`
+        );
+      } else {
+        assert_in_array(
+          editor.innerHTML,
+          [
+            `${openTagOfContainer}<br>${closeAndOpenTagsOfSplitPoint}<${tag}>${closeTagOfContainer}`,
+            `${openTagOfContainer}<br>${closeAndOpenTagsOfSplitPoint}<${tag}><br>${closeTagOfContainer}`,
+          ],
+          `The paragraph should be inserted before the <${tag}> element`
+        );
+      }
+    }, `Inserting paragraph when selection is collapsed in <${tag}> in <${container}> which is only child (explicitly flushes maybe pending layout)`);
+
     test(() => {
       editor.innerHTML = `${openTagOfContainer}abc<${tag}>${closeTagOfContainer}`;
       const element = editor.querySelector(tag);

testing/web-platform/tests/editing/other/insert-text-in-void-element.tentative.html

@@ -56,6 +56,36 @@ for (const tag of voidElements) {
     }
   }, `Inserting text when selection is collapsed in <${tag}> which is only child`);
 
+  test(() => {
+    editor.innerHTML = `<div></div>`;
+    const element = document.createElement(tag);
+    editor.firstChild.appendChild(element);
+    editor.focus();
+    const selection = getSelection();
+    selection.collapse(element, 0);
+    element.getBoundingClientRect();
+    document.execCommand("insertText", false, "abc");
+    if (tag == "br") {
+      assert_in_array(
+        editor.innerHTML,
+        [
+          "<div>abc</div>",
+          "<div>abc<br></div>",
+        ],
+        `The text should be inserted before the <br> element`
+      );
+    } else {
+      assert_in_array(
+        editor.innerHTML,
+        [
+          `<div>abc<${tag}></div>`,
+          `<div>abc<${tag}><br></div>`,
+        ],
+        `The text should be inserted before the <${tag}> element`
+      );
+    }
+  }, `Inserting text when selection is collapsed in <${tag}> which is only child (explicitly flushes maybe pending layout)`);
+
   test(() => {
     editor.innerHTML = `<div>abc</div>`;
     const element = document.createElement(tag);