Fixes runtime error when cutting empty selection at the end of the content

Summary: This diff introduces an undesired behavior introduced by D13085302 where the removeRange operation triggers an error if the selection is collapsed at the end of the last content block.

Reviewed By: elboman

Differential Revision: D15758815

fbshipit-source-id: 0f0c2cc94aed23643efb36a66587189e624addc6

Author: Claudio Procida

src/component/handlers/edit/commands/SecondaryClipboard.js

@@ -37,9 +37,11 @@ const SecondaryClipboard = {
       const blockEnd = content.getBlockForKey(anchorKey).getLength();
 
       if (blockEnd === selection.getAnchorOffset()) {
-        targetRange = selection
-          .set('focusKey', content.getKeyAfter(anchorKey))
-          .set('focusOffset', 0);
+        const keyAfter = content.getKeyAfter(anchorKey);
+        if (keyAfter == null) {
+          return editorState;
+        }
+        targetRange = selection.set('focusKey', keyAfter).set('focusOffset', 0);
       } else {
         targetRange = selection.set('focusOffset', blockEnd);
       }

src/component/handlers/edit/commands/__tests__/SecondaryClipboard-test.js

@@ -0,0 +1,150 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @emails oncall+draft_js
+ * @format
+ * @flow strict-local
+ */
+
+'use strict';
+
+jest.disableAutomock();
+
+jest.mock('generateRandomKey');
+
+const toggleExperimentalTreeDataSupport = enabled => {
+  jest.doMock('gkx', () => name => {
+    return name === 'draft_tree_data_support' ? enabled : false;
+  });
+};
+
+// Seems to be important to put this at the top
+toggleExperimentalTreeDataSupport(true);
+
+const BlockMapBuilder = require('BlockMapBuilder');
+const ContentBlockNode = require('ContentBlockNode');
+const EditorState = require('EditorState');
+const SecondaryClipboard = require('SecondaryClipboard');
+const SelectionState = require('SelectionState');
+
+const getSampleStateForTesting = require('getSampleStateForTesting');
+const Immutable = require('immutable');
+
+const {List} = Immutable;
+
+const {contentState} = getSampleStateForTesting();
+
+const contentBlockNodes = [
+  new ContentBlockNode({
+    key: 'A',
+    nextSibling: 'B',
+    text: 'Alpha',
+    type: 'blockquote',
+  }),
+  new ContentBlockNode({
+    key: 'B',
+    prevSibling: 'A',
+    nextSibling: 'G',
+    type: 'ordered-list-item',
+    children: List(['C', 'F']),
+  }),
+  new ContentBlockNode({
+    parent: 'B',
+    key: 'C',
+    nextSibling: 'F',
+    type: 'blockquote',
+    children: List(['D', 'E']),
+  }),
+  new ContentBlockNode({
+    parent: 'C',
+    key: 'D',
+    nextSibling: 'E',
+    type: 'header-two',
+    text: 'Delta',
+  }),
+  new ContentBlockNode({
+    parent: 'C',
+    key: 'E',
+    prevSibling: 'D',
+    type: 'unstyled',
+    text: 'Elephant',
+  }),
+  new ContentBlockNode({
+    parent: 'B',
+    key: 'F',
+    prevSibling: 'C',
+    type: 'code-block',
+    text: 'Fire',
+  }),
+  new ContentBlockNode({
+    key: 'G',
+    prevSibling: 'B',
+    nextSibling: 'H',
+    type: 'ordered-list-item',
+    text: 'Gorila',
+  }),
+  new ContentBlockNode({
+    key: 'H',
+    prevSibling: 'G',
+    nextSibling: 'I',
+    text: ' ',
+    type: 'atomic',
+  }),
+  new ContentBlockNode({
+    key: 'I',
+    prevSibling: 'H',
+    text: 'last',
+    type: 'unstyled',
+  }),
+];
+
+const assertCutOperation = (
+  operation,
+  selection = {},
+  content = contentBlockNodes,
+) => {
+  const result = operation(
+    EditorState.forceSelection(
+      EditorState.createWithContent(
+        contentState.set('blockMap', BlockMapBuilder.createFromArray(content)),
+      ),
+      SelectionState.createEmpty(content[0].key).merge(selection),
+    ),
+  );
+  const expected = result
+    .getCurrentContent()
+    .getBlockMap()
+    .toJS();
+
+  expect(expected).toMatchSnapshot();
+};
+
+test(`in the middle of a block, cut removes the remainder of the block`, () => {
+  assertCutOperation(editorState => SecondaryClipboard.cut(editorState), {
+    anchorKey: 'E',
+    anchorOffset: contentBlockNodes[4].getLength() - 2,
+    focusKey: 'E',
+    focusOffset: contentBlockNodes[4].getLength() - 2,
+  });
+});
+
+test(`at the end of an intermediate block, cut merges with the adjacent content block`, () => {
+  assertCutOperation(editorState => SecondaryClipboard.cut(editorState), {
+    anchorKey: 'H',
+    anchorOffset: contentBlockNodes[7].getLength(),
+    focusKey: 'H',
+    focusOffset: contentBlockNodes[7].getLength(),
+  });
+});
+
+test(`at the end of the last block, cut is a no-op`, () => {
+  assertCutOperation(editorState => SecondaryClipboard.cut(editorState), {
+    anchorKey: 'I',
+    anchorOffset: contentBlockNodes[8].getLength(),
+    focusKey: 'I',
+    focusOffset: contentBlockNodes[8].getLength(),
+  });
+});