HtmlEditor in Edge - Should no trigger errors when text prediction en…

…abled(T1200561) (#109)

core/editor.js

@@ -9,6 +9,7 @@ import Block, { BlockEmbed, bubbleFormats } from '../blots/block';
 import Break from '../blots/break';
 import TextBlot, { escapeText } from '../blots/text';
 import removeClass from '../utils/remove_class';
+import isDefined from '../utils/is_defined';
 
 const ASCII = /^[ -~]*$/;
 
@@ -243,11 +244,18 @@ class Editor {
     } else {
       this.delta = this.getDelta();
       if (!change || !isEqual(oldDelta.compose(change), this.delta)) {
-        change = oldDelta.diff(this.delta, selectionInfo);
+        if (!this.deltaContainsRetain(oldDelta)) {
+          change = oldDelta.diff(this.delta, selectionInfo);
+        }
       }
     }
     return change;
   }
+
+  // T1200561
+  deltaContainsRetain(delta) {
+    return delta.ops.some((op) => isDefined(op.retain));
+  }
 }
 
 function convertListHTML(items, lastIndent, types) {

test/unit/core/editor.js

@@ -295,6 +295,61 @@ describe('Editor', function () {
     });
   });
 
+  // T1200561
+  describe('deltaContainsRetain functionality', function () {
+    it('delta should be empty when deltaContainsRetain returns false(T1200561)', function () {
+      const editor = this.initialize(Editor, '<p></p>');
+
+      editor.deltaContainsRetain = () => {
+        return false;
+      };
+
+      const sourceDelta = new Delta().insert('123');
+      editor.update(sourceDelta);
+
+      const newDelta = new Delta().insert('new string');
+
+      const resultDelta = editor.update(newDelta);
+
+      expect(resultDelta.ops.length).toEqual(0);
+    });
+
+    it('delta should be empty when deltaContainsRetain returns true(T1200561)', function () {
+      const editor = this.initialize(Editor, '<p></p>');
+
+      editor.deltaContainsRetain = () => {
+        return true;
+      };
+
+      const sourceDelta = new Delta().insert('123');
+      editor.update(sourceDelta);
+
+      const newDelta = new Delta().insert('new string');
+
+      const resultDelta = editor.update(newDelta);
+
+      expect(resultDelta.ops.length).toEqual(1);
+    });
+
+    it('deltaContainsRetain should return true when delta contains retain operation(T1200561)', function () {
+      const editor = this.initialize(Editor, '<p></p>');
+      const delta = new Delta().retain(3);
+
+      const deltaContainsRetain = editor.deltaContainsRetain(delta);
+
+      expect(deltaContainsRetain).toEqual(true);
+    });
+
+    it('deltaContainsRetain should return false when delta not contains retain operation(T1200561)', function () {
+      const editor = this.initialize(Editor, '<p></p>');
+      const delta = new Delta().insert('123');
+
+      const deltaContainsRetain = editor.deltaContainsRetain(delta);
+
+      expect(deltaContainsRetain).toEqual(false);
+    });
+  });
+
   describe('applyDelta', function () {
     it('insert', function () {
       const editor = this.initialize(Editor, '<p></p>');