Apply no-children normalization fix before normalization (#4208)

* Test cases for failure condition

* Before normalizing ensure all elements have at least one text child. This is a normalization requirement that some normalization fixes require, so it must be done as an initial dedicated pass.

.changeset/silver-snakes-perform.md

@@ -0,0 +1,5 @@
+---
+'slate': patch
+---
+
+Fix `Error: Cannot get the start point in the node at path [...] because it has no start text node` caused by normalizing a document where some elements have no children

packages/slate/src/interfaces/editor.ts

@@ -16,6 +16,7 @@ import {
   RangeRef,
   Span,
   Text,
+  Transforms,
 } from '..'
 import {
   DIRTY_PATHS,
@@ -988,6 +989,27 @@ export const Editor: EditorInterface = {
     }
 
     Editor.withoutNormalizing(editor, () => {
+      /*
+        Fix dirty elements with no children.
+        editor.normalizeNode() does fix this, but some normalization fixes also require it to work.
+        Running an initial pass avoids the catch-22 race condition.
+      */
+      for (const dirtyPath of getDirtyPaths(editor)) {
+        if (Node.has(editor, dirtyPath)) {
+          const [node, _] = Editor.node(editor, dirtyPath)
+
+          // Add a text child to elements with no children.
+          // This is safe to do in any order, by definition it can't cause other paths to change.
+          if (Element.isElement(node) && node.children.length === 0) {
+            const child = { text: '' }
+            Transforms.insertNodes(editor, child, {
+              at: dirtyPath.concat(0),
+              voids: true,
+            })
+          }
+        }
+      }
+
       const max = getDirtyPaths(editor).length * 42 // HACK: better way?
       let m = 0
 

packages/slate/test/transforms/normalization/move_node.tsx

@@ -0,0 +1,21 @@
+/** @jsx jsx */
+import { Transforms } from 'slate'
+import { jsx } from '../..'
+
+export const input = (
+  <editor>
+    <block>one</block>
+    <block>two</block>
+  </editor>
+)
+export const run = editor => {
+  Transforms.moveNodes(editor, { at: [0, 0], to: [1, 0] })
+}
+export const output = (
+  <editor>
+    <block>
+      <text />
+    </block>
+    <block>onetwo</block>
+  </editor>
+)

packages/slate/test/transforms/normalization/split_node-and-insert_node.tsx

@@ -0,0 +1,84 @@
+/** @jsx jsx */
+import { Editor, Transforms } from 'slate'
+import { jsx } from '../..'
+
+export const input = (
+  <editor>
+    <block>
+      <text />
+      <inline>one</inline>
+      <text />
+    </block>
+    <block>
+      <text />
+      <inline>two</inline>
+      <text />
+    </block>
+  </editor>
+)
+export const run = editor => {
+  Editor.withoutNormalizing(editor, () => {
+    const operations = [
+      {
+        type: 'split_node',
+        path: [0, 1],
+        position: 0,
+        properties: { inline: true },
+      },
+      {
+        type: 'split_node',
+        path: [0],
+        position: 1,
+        properties: {},
+      },
+      {
+        type: 'split_node',
+        path: [2, 1, 0],
+        position: 0,
+        properties: {},
+      },
+      {
+        type: 'split_node',
+        path: [2, 1],
+        position: 0,
+        properties: { inline: true },
+      },
+      {
+        type: 'split_node',
+        path: [2],
+        position: 1,
+        properties: {},
+      },
+      { type: 'insert_node', path: [2, 1], node: { text: '' } },
+    ]
+    operations.forEach(editor.apply)
+  })
+}
+export const output = (
+  <editor>
+    <block>
+      <text />
+    </block>
+    <block>
+      <text />
+      <inline>
+        <text />
+      </inline>
+      <text />
+      <inline>one</inline>
+      <text />
+    </block>
+    <block>
+      <text />
+    </block>
+    <block>
+      <text />
+      <inline>
+        <text />
+      </inline>
+      <text />
+      <inline>two</inline>
+      <text />
+    </block>
+  </editor>
+)