imp(dom-adapters): save formatting on block split

Author: e11sy

packages/dom-adapters/src/BlockToolAdapter/index.ts

@@ -349,6 +349,16 @@ export class BlockToolAdapter implements BlockToolAdapterInterface {
     const currentValue = this.#model.getText(this.#blockIndex, key);
     const newValueAfter = currentValue.slice(end);
 
+    const relatedFragments = this.#model.getFragments(this.#blockIndex, key, start, currentValue.length);
+
+    /**
+     * Adjust fragments ranges respectfully to the removed text
+     */
+    relatedFragments.forEach(fragment => {
+      fragment.range[0] = Math.max(0, fragment.range[0] - end);
+      fragment.range[1] -= end;
+    });
+
     this.#model.removeText(this.#config.userId, this.#blockIndex, key, start, currentValue.length);
     this.#model.addBlock(
       this.#config.userId,
@@ -358,7 +368,7 @@ export class BlockToolAdapter implements BlockToolAdapterInterface {
           [key]: {
             $t: 't',
             value: newValueAfter,
-            fragments: [],
+            fragments: relatedFragments,
           },
         },
       },