Added tests and fixed IE IndexSizeError trying to get a range from a selection when there is not one (facebookarchive#2271)

Summary:
**Summary**
Various browsers will throw errors if `selection.getRangeAt(0)` is called when there is no range. To fix this, a check was added to make sure a range exists.

This change was originally suggested [here](facebookarchive#1571) a few years ago. I opted for opening a new PR and adding tests here since that PR seemed stale.

Selection and Range did not work in the test environment, so I had to stub them. I only added functionality for what was needed in the tests I added, but more can be added in the future very easily.
Pull Request resolved: facebookarchive#2271

Differential Revision: D18807105

Pulled By: mrkev

fbshipit-source-id: 0e3b833b8a3267b9a5f17b262b6a0442b6ae5e3d

Author: LaurenWyatt610

src/component/contents/DraftEditorLeaf.react.js

@@ -20,7 +20,8 @@ const React = require('React');
 
 const invariant = require('invariant');
 const isHTMLBRElement = require('isHTMLBRElement');
-const setDraftEditorSelection = require('setDraftEditorSelection');
+const setDraftEditorSelection = require('setDraftEditorSelection')
+  .setDraftEditorSelection;
 
 type Props = {
   // The block that contains this leaf.

src/component/selection/__tests__/__snapshots__/setDraftEditorSelection-test.js.snap

@@ -0,0 +1,23 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`addFocusToSelection sets a new focus on the selection if selection.extend is unsupported 1`] = `
+Selection {
+  "focusNode": Washington,
+  "focusOffset": 0,
+  "range": Range {
+    "endOffset": 3,
+    "node": Washington,
+    "startOffset": 0,
+  },
+  "rangeCount": 1,
+}
+`;
+
+exports[`addFocusToSelection the range is not updated if rangeCount is 0 1`] = `
+Selection {
+  "focusNode": null,
+  "focusOffset": 0,
+  "range": null,
+  "rangeCount": 0,
+}
+`;

src/component/selection/__tests__/setDraftEditorSelection-test.js

@@ -0,0 +1,106 @@
+/**
+ * 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
+ */
+
+'use strict';
+
+jest.disableAutomock();
+
+const addFocusToSelection = require('setDraftEditorSelection')
+  .addFocusToSelection;
+const getSampleSelectionMocksForTesting = require('getSampleSelectionMocksForTesting');
+
+// Based on https://w3c.github.io/selection-api/#selection-interface
+class Selection {
+  constructor({range}) {
+    this.rangeCount = range ? 1 : 0;
+    this.focusNode = (range && range.node) || null;
+    this.focusOffset = (range && range.startOffset) || 0;
+    this.range = range || null;
+  }
+
+  getRangeAt(idx) {
+    if (idx !== 0 || this.rangeCount <= 0) {
+      throw new Error('IndexSizeError');
+    }
+    return this.range;
+  }
+
+  addRange(range) {
+    this.range = range;
+    this.rangeCount = 1;
+  }
+}
+
+// Based on https://dom.spec.whatwg.org/#concept-range
+class Range {
+  constructor({startOffset, endOffset, node}) {
+    this.startOffset = startOffset;
+    this.endOffset = endOffset;
+    this.node = node;
+  }
+
+  setEnd(node, offset) {
+    this.endOffset = offset;
+    this.node = node;
+  }
+
+  cloneRange() {
+    return new Range({
+      startOffset: this.startOffset,
+      endOffset: this.endOffset,
+      node: this.node,
+    });
+  }
+}
+
+let editorState = null;
+let textNodes = null;
+
+const resetRootNodeMocks = () => {
+  ({editorState, textNodes} = getSampleSelectionMocksForTesting());
+};
+
+beforeEach(() => {
+  resetRootNodeMocks();
+});
+
+describe('addFocusToSelection', () => {
+  test('sets a new focus on the selection if selection.extend is unsupported', () => {
+    const range = new Range({
+      startOffset: 0,
+      endOffset: 0,
+      node: textNodes[0],
+    });
+    const selection = new Selection({range});
+    const storedFocusNode = selection.focusNode;
+    const storedFocusOffset = 3;
+    addFocusToSelection(
+      selection,
+      storedFocusNode,
+      storedFocusOffset,
+      editorState.getSelection(),
+    );
+    expect(selection).toMatchSnapshot();
+  });
+
+  // If rangeCount is 0, selection.getRangeAt() will throw on various browsers
+  test('the range is not updated if rangeCount is 0', () => {
+    const selection = new Selection({});
+    const storedFocusNode = selection.focusNode;
+    const storedFocusOffset = 3;
+    addFocusToSelection(
+      selection,
+      storedFocusNode,
+      storedFocusOffset,
+      editorState.getSelection(),
+    );
+    expect(selection).toMatchSnapshot();
+  });
+});

src/component/selection/setDraftEditorSelection.js

@@ -306,9 +306,11 @@ function addFocusToSelection(
     // Additionally, clone the selection range. IE11 throws an
     // InvalidStateError when attempting to access selection properties
     // after the range is detached.
-    const range = selection.getRangeAt(0);
-    range.setEnd(node, offset);
-    selection.addRange(range.cloneRange());
+    if (selection.rangeCount > 0) {
+      const range = selection.getRangeAt(0);
+      range.setEnd(node, offset);
+      selection.addRange(range.cloneRange());
+    }
   }
 }
 
@@ -333,4 +335,7 @@ function addPointToSelection(
   selection.addRange(range);
 }
 
-module.exports = setDraftEditorSelection;
+module.exports = {
+  setDraftEditorSelection,
+  addFocusToSelection,
+};