Markdown stability patch (#7238)

* fix: enforce empty paragraph when converting from markdown to slate

* fix: handle unwrapping inline nodes in lists

* style: lint code

* fix: lost focus after backspace after break

Author: demshy

packages/decap-cms-widget-markdown/src/MarkdownControl/plugins/blocks/events/keyDown.js

@@ -1,9 +1,11 @@
 import isHotkey from 'is-hotkey';
+import { Editor, Transforms } from 'slate';
 
 import keyDownEnter from './keyDownEnter';
 import keyDownBackspace from './keyDownBackspace';
 import isCursorInNonDefaultBlock from '../locations/isCursorInNonDefaultBlock';
 import toggleBlock from './toggleBlock';
+import isCursorCollapsedAfterSoftBreak from '../locations/isCursorCollapsedAfterSoftBreak';
 
 const HEADING_HOTKEYS = {
   'mod+1': 'heading-one',
@@ -25,6 +27,13 @@ function keyDown(event, editor) {
     }
   }
 
+  if (isHotkey('backspace', event) && isCursorCollapsedAfterSoftBreak(editor)) {
+    const [, path] = Editor.previous(editor);
+    Transforms.removeNodes(editor, { at: path });
+    event.preventDefault();
+    return false;
+  }
+
   if (!isCursorInNonDefaultBlock(editor)) return;
 
   if (isHotkey('enter', event)) {

packages/decap-cms-widget-markdown/src/MarkdownControl/plugins/blocks/locations/isCursorCollapsedAfterSoftBreak.js

@@ -0,0 +1,13 @@
+import { Editor, Range } from 'slate';
+
+function isCursorCollapsedAfterSoftBreak(editor) {
+  const { selection } = editor;
+  if (!selection) return false;
+  if (Range.isExpanded(selection)) return false;
+
+  const previous = Editor.previous(editor);
+
+  return previous && previous[0].type == 'break';
+}
+
+export default isCursorCollapsedAfterSoftBreak;

packages/decap-cms-widget-markdown/src/MarkdownControl/plugins/blocks/transforms/unwrapIfCursorAtStart.js

@@ -5,18 +5,31 @@ import lowestMatchedAncestor from '../../matchers/lowestMatchedAncestor';
 function unwrapIfCursorAtStart(editor, mergeWithPrevious = false) {
   if (editor.selection.anchor.offset !== 0) return false;
 
-  const node = Editor.above(editor, lowestMatchedAncestor(editor, 'non-default'));
+  let [node, path] = Editor.above(editor, lowestMatchedAncestor(editor, 'non-default'));
 
-  if (node[1].length == 0) return false;
+  if (path.length == 0) return false;
 
-  const isHeading = `${node[0].type}`.startsWith('heading-');
+  const isHeading = `${node.type}`.startsWith('heading-');
   if (isHeading) {
     Transforms.setNodes(editor, { type: 'paragraph' });
     return false;
   }
 
+  const isBlock = Editor.isBlock(editor, node);
+  const [parentBlock, parentBlockPath] = Editor.above(
+    editor,
+    lowestMatchedAncestor(editor, 'block'),
+  );
+  if (!isBlock) {
+    if (!Editor.isStart(editor, path, parentBlockPath)) {
+      return false;
+    }
+
+    [node, path] = [parentBlock, parentBlockPath];
+  }
+
   Editor.withoutNormalizing(editor, () => {
-    Transforms.unwrapNodes(editor, { match: n => n.type === node[0].type, split: true });
+    Transforms.unwrapNodes(editor, { match: n => n.type === node.type, split: true });
 
     if (mergeWithPrevious) {
       Transforms.mergeNodes(editor);

packages/decap-cms-widget-markdown/src/serializers/remarkSlate.js

@@ -234,14 +234,22 @@ export default function remarkToSlate({ voidCodeBlock } = {}) {
        * Convert simple cases that only require a type and children, with no
        * additional properties.
        */
-      case 'root':
       case 'paragraph':
       case 'blockquote':
       case 'tableRow':
       case 'tableCell': {
         return createBlock(typeMap[node.type], nodes);
       }
 
+      /**
+       * Root element
+       * If the root node is empty, we need to add a paragraph node to it.
+       */
+      case 'root': {
+        const children = isEmpty(nodes) ? [createBlock('paragraph')] : nodes;
+        return createBlock(typeMap[node.type], children);
+      }
+
       /**
        * List Items
        *