feat(core): recover entry after unexpected quit (#2129)

packages/netlify-cms-widget-markdown/src/MarkdownControl/VisualEditor.js

@@ -2,7 +2,7 @@ import React from 'react';
 import PropTypes from 'prop-types';
 import ImmutablePropTypes from 'react-immutable-proptypes';
 import styled, { cx } from 'react-emotion';
-import { get, isEmpty, debounce } from 'lodash';
+import { get, isEmpty, debounce, uniq } from 'lodash';
 import { List } from 'immutable';
 import { Value, Document, Block, Text } from 'slate';
 import { Editor as Slate } from 'slate-react';
@@ -48,11 +48,41 @@ export default class Editor extends React.Component {
     super(props);
     this.state = {
       value: createSlateValue(props.value),
+      lastRawValue: props.value,
     };
   }
 
   shouldComponentUpdate(nextProps, nextState) {
-    return !this.state.value.equals(nextState.value);
+    const forcePropsValue = this.shouldForcePropsValue(
+      this.props.value,
+      this.state.lastRawValue,
+      nextProps.value,
+      nextState.lastRawValue,
+    );
+    return !this.state.value.equals(nextState.value) || forcePropsValue;
+  }
+
+  componentDidUpdate(prevProps, prevState) {
+    const forcePropsValue = this.shouldForcePropsValue(
+      prevProps.value,
+      prevState.lastRawValue,
+      this.props.value,
+      this.state.lastRawValue,
+    );
+
+    if (forcePropsValue) {
+      this.setState({ value: createSlateValue(this.props.value) });
+    }
+  }
+
+  // If the old props/state values and new state value are all the same, and
+  // the new props value does not match the others, the new props value
+  // originated from outside of this widget and should be used.
+  shouldForcePropsValue(oldPropsValue, oldStateValue, newPropsValue, newStateValue) {
+    return (
+      uniq([oldPropsValue, oldStateValue, newStateValue]).length === 1 &&
+      oldPropsValue !== newPropsValue
+    );
   }
 
   handlePaste = (e, data, change) => {
@@ -194,7 +224,7 @@ export default class Editor extends React.Component {
     const { onChange } = this.props;
     const raw = change.value.document.toJSON();
     const markdown = slateToMarkdown(raw);
-    onChange(markdown);
+    this.setState({ lastRawValue: markdown }, () => onChange(markdown));
   }, 150);
 
   handleChange = change => {