fix: getPos race condition in React StrictMode (#2311)

Author: YousefED

tests/src/unit/react/BlockNoteViewRapidRemount.test.tsx

@@ -0,0 +1,89 @@
+import { BlockNoteEditor, BlockNoteSchema } from "@blocknote/core";
+import { BlockNoteView } from "@blocknote/mantine";
+import "@blocknote/mantine/style.css";
+import { createReactBlockSpec } from "@blocknote/react";
+import { StrictMode } from "react";
+import { flushSync } from "react-dom";
+import { createRoot } from "react-dom/client";
+import { afterEach, beforeEach, describe, it } from "vitest";
+
+describe("BlockNoteView Rapid Remount", () => {
+  let div: HTMLDivElement;
+
+  beforeEach(() => {
+    div = document.createElement("div");
+    document.body.appendChild(div);
+  });
+
+  afterEach(() => {
+    document.body.removeChild(div);
+  });
+
+  it("should not crash when remounting BlockNoteView with custom blocks rapidly", async () => {
+    // Define a custom block that might be sensitive to lifecycle
+    const Alert = createReactBlockSpec(
+      {
+        type: "alert",
+        propSchema: {
+          type: {
+            default: "warning",
+          },
+        },
+        content: "inline",
+      },
+      {
+        render: (props) => {
+          return (
+            <div className={"alert"}>
+              <div className={"inline-content"} ref={props.contentRef} />
+            </div>
+          );
+        },
+      },
+    );
+
+    const schema = BlockNoteSchema.create().extend({
+      blockSpecs: {
+        alert: Alert(),
+      },
+    });
+
+    const editor = BlockNoteEditor.create({
+      schema,
+      initialContent: [
+        {
+          type: "paragraph",
+          content: "Text before",
+        },
+        {
+          type: "alert",
+          content: "Hello World 1",
+        },
+        {
+          type: "alert",
+          content: "Hello World 2",
+        },
+        {
+          type: "paragraph",
+          content: "Text after",
+        },
+      ],
+    });
+
+    const root = createRoot(div);
+
+    // Simulate rapid key changes (remounts)
+    for (let i = 0; i < 20; i++) {
+      flushSync(() => {
+        root.render(
+          <StrictMode>
+            <BlockNoteView editor={editor} key={i} />
+          </StrictMode>,
+        );
+      });
+      // yield to event loop to allow effects to run, triggering the race condition
+      await new Promise((r) => setTimeout(r, 0));
+    }
+    root.unmount();
+  });
+});