Remove non-leaf blocks in tree => raw conversion

Summary:
The raw => tree data conversion creates new parent blocks because nodes with content on them (leaf nodes) aren't allowed to have children. When we convert to back to raw mode, we need to get rid of these extra non-leaf nodes, otherwise they get rendered.

Also fixed the test cases to respect the tree invariants.

Reviewed By: mitermayer

Differential Revision: D9567760

fbshipit-source-id: 6b53fba057dedeabad63a2492748fc1958b71a96

Author: niveditc

src/component/utils/exploration/DraftTreeAdapter.js

@@ -85,6 +85,11 @@ const DraftTreeAdapter = {
       if (isListBlock(block)) {
         newBlock.depth = newBlock.depth || 0;
         addDepthToChildren(block);
+
+        // if it's a non-leaf node, we don't do anything else
+        if (block.children != null && block.children.length > 0) {
+          return;
+        }
       }
 
       delete newBlock.children;

src/component/utils/exploration/__tests__/DraftTreeAdapter-test.js

@@ -51,6 +51,7 @@ test('must be able to convert from tree raw state with only root blocks to raw s
 });
 
 test('must be able to convert from tree raw state with nested blocks to raw state', () => {
+  // Right now, we ignore non-list nested blocks
   const rawState = {
     blocks: [
       {
@@ -80,17 +81,35 @@ test('must be able to convert from tree raw state with nested blocks to raw stat
 });
 
 test('must be able to convert from tree raw state with nested list blocks to raw state preserving lists depth', () => {
+  /**
+   * 1. Alpha
+   *   a. Beta
+   *     i. Charlie
+   *   b. Delta
+   */
   const rawState = {
     blocks: [
       {
         key: 'A',
         type: 'ordered-list-item',
         text: 'Alpha',
+        children: [],
+      },
+      {
+        key: 'X',
+        text: '',
+        type: 'ordered-list-item',
         children: [
           {
             key: 'B',
+            type: 'ordered-list-item',
             text: 'Beta',
+            children: [],
+          },
+          {
+            key: 'Y',
             type: 'ordered-list-item',
+            text: '',
             children: [
               {
                 key: 'C',
@@ -122,11 +141,23 @@ test('must be able to convert from tree raw state with nested list blocks to raw
         key: 'A',
         type: 'ordered-list-item',
         text: 'Alpha',
+        children: [],
+      },
+      {
+        key: 'X',
+        type: 'ordered-list-item',
+        text: '',
         children: [
           {
             key: 'B',
             text: 'Beta',
             type: 'ordered-list-item',
+            children: [],
+          },
+          {
+            key: 'Y',
+            type: 'ordered-list-item',
+            text: '',
             children: [
               {
                 key: 'C',