chore: Fix warning of findDOMNode (#419)

* fix: findDOMNode should only work on validate element

* fix: find logic

Author: zombieJ

src/Dom/findDOMNode.ts

@@ -1,3 +1,4 @@
+import React from 'react';
 import ReactDOM from 'react-dom';
 
 /**
@@ -7,7 +8,12 @@ export default function findDOMNode<T = Element | Text>(
   node: React.ReactInstance | HTMLElement,
 ): T {
   if (node instanceof HTMLElement) {
-    return (node as unknown) as T;
+    return node as unknown as T;
   }
-  return (ReactDOM.findDOMNode(node) as unknown) as T;
+
+  if (node instanceof React.Component) {
+    return ReactDOM.findDOMNode(node) as unknown as T;
+  }
+
+  return null;
 }

tests/findDOMNode.test.tsx

@@ -0,0 +1,58 @@
+import * as React from 'react';
+import { render } from '@testing-library/react';
+import findDOMNode from '../src/Dom/findDOMNode';
+
+describe('findDOMNode', () => {
+  it('base work', () => {
+    const errSpy = jest.spyOn(console, 'error').mockImplementation(() => {});
+
+    const divRef = React.createRef<HTMLDivElement>();
+    const { container } = render(
+      <React.StrictMode>
+        <div ref={divRef} />
+      </React.StrictMode>,
+    );
+
+    const ele = findDOMNode(divRef.current);
+    expect(container.firstChild).toBe(ele);
+
+    expect(errSpy).not.toHaveBeenCalled();
+    errSpy.mockRestore();
+  });
+
+  it('not throw if is not a React obj', () => {
+    const errSpy = jest.spyOn(console, 'error').mockImplementation(() => {});
+
+    const empty = findDOMNode({} as any);
+    expect(empty).toBeNull();
+
+    expect(errSpy).not.toHaveBeenCalled();
+    errSpy.mockRestore();
+  });
+
+  it('class component', () => {
+    const errSpy = jest.spyOn(console, 'error').mockImplementation(() => {});
+
+    class DOMWrapper extends React.Component {
+      getDOM = () => {
+        return findDOMNode(this);
+      };
+
+      render() {
+        return <div />;
+      }
+    }
+
+    const wrapperRef = React.createRef<DOMWrapper>();
+    const { container } = render(
+      <React.StrictMode>
+        <DOMWrapper ref={wrapperRef} />
+      </React.StrictMode>,
+    );
+
+    expect(wrapperRef.current!.getDOM()).toBe(container.firstChild);
+
+    expect(errSpy).toHaveBeenCalled();
+    errSpy.mockRestore();
+  });
+});