feat(jsx/dom): skip calculate children if props are the same

src/jsx/dom/hooks/index.test.tsx

@@ -1,6 +1,6 @@
 /** @jsxImportSource ../../ */
 import { JSDOM } from 'jsdom'
-import { render, useState } from '..'
+import { render, useCallback, useState } from '..'
 import { useActionState, useFormStatus, useOptimistic } from '.'
 
 describe('Hooks', () => {
@@ -84,14 +84,13 @@ describe('Hooks', () => {
       }
       const App = () => {
         const [, setCount] = useState(0)
+        const action = useCallback(() => {
+          setCount((count) => count + 1)
+          return formPromise
+        }, [])
         return (
           <>
-            <form
-              action={() => {
-                setCount((count) => count + 1)
-                return formPromise
-              }}
-            >
+            <form action={action}>
               <Status />
               <input type='text' name='name' value='updated' />
               <button>Submit</button>
@@ -134,15 +133,15 @@ describe('Hooks', () => {
       const App = () => {
         const [count, setCount] = useState(0)
         const [optimisticCount, setOptimisticCount] = useOptimistic(count, (c, n: number) => n)
+        const action = useCallback(async () => {
+          setOptimisticCount(count + 1)
+          await formPromise
+          setCount((count) => count + 2)
+        }, [])
+
         return (
           <>
-            <form
-              action={async () => {
-                setOptimisticCount(count + 1)
-                await formPromise
-                setCount((count) => count + 2)
-              }}
-            >
+            <form action={action}>
               <div>{optimisticCount}</div>
               <input type='text' name='name' value='updated' />
               <button>Submit</button>

src/jsx/dom/index.test.tsx

@@ -264,6 +264,33 @@ describe('DOM', () => {
     })
   })
 
+  describe('skip build child', () => {
+    it('simple', async () => {
+      const Child = vi.fn(({ count }: { count: number }) => <div>{count}</div>)
+      const App = () => {
+        const [count, setCount] = useState(0)
+        return (
+          <>
+            <div>{count}</div>
+            <Child count={Math.floor(count / 2)} />
+            <button onClick={() => setCount(count + 1)}>+</button>
+          </>
+        )
+      }
+      render(<App />, root)
+      expect(root.innerHTML).toBe('<div>0</div><div>0</div><button>+</button>')
+      expect(Child).toBeCalledTimes(1)
+      root.querySelector('button')?.click()
+      await Promise.resolve()
+      expect(root.innerHTML).toBe('<div>1</div><div>0</div><button>+</button>')
+      expect(Child).toBeCalledTimes(1)
+      root.querySelector('button')?.click()
+      await Promise.resolve()
+      expect(root.innerHTML).toBe('<div>2</div><div>1</div><button>+</button>')
+      expect(Child).toBeCalledTimes(2)
+    })
+  })
+
   describe('defaultProps', () => {
     it('simple', () => {
       const App: FC<{ name?: string }> = ({ name }) => <div>{name}</div>

src/jsx/dom/intrinsic-element/components.ts

@@ -277,7 +277,7 @@ export const form: FC<
     ;(restProps as any).action = action
   }
 
-  const [data, setData] = useState<FormData | null>(null)
+  const [state, setState] = useState<[FormData | null, boolean]>([null, false]) // [FormData, isDirty]
   const onSubmit = useCallback<(ev: SubmitEvent | CustomEvent) => void>(
     async (ev: SubmitEvent | CustomEvent) => {
       const currentAction = ev.isTrusted
@@ -289,13 +289,13 @@ export const form: FC<
 
       ev.preventDefault()
       const formData = new FormData(ev.target as HTMLFormElement)
-      setData(formData)
+      setState([formData, true])
       const actionRes = currentAction(formData)
       if (actionRes instanceof Promise) {
         registerAction(actionRes)
         await actionRes
       }
-      setData(null)
+      setState([null, true])
     },
     []
   )
@@ -307,6 +307,8 @@ export const form: FC<
     }
   })
 
+  const [data, isDirty] = state
+  state[1] = false
   return newJSXNode({
     tag: FormContext as unknown as Function,
     props: {
@@ -324,8 +326,9 @@ export const form: FC<
         },
       }),
     },
+    f: isDirty,
     // eslint-disable-next-line @typescript-eslint/no-explicit-any
-  }) as any
+  } as any) as any
 }
 
 const formActionableElement = (

src/jsx/dom/render.ts

@@ -43,6 +43,7 @@ export type NodeObject = {
   vR: Node[] // virtual dom children to remove
   s?: Node[] // shadow virtual dom children
   n?: string // namespace
+  f?: boolean // force build
   c: Container | undefined // container
   e: SupportedElement | Text | undefined // rendered element
   p?: PreserveNodeType // preserve HTMLElement if it will be unmounted
@@ -444,6 +445,7 @@ export const build = (context: Context, node: NodeObject, children?: Child[]): v
           oldVChildren.splice(i, 1)
         }
 
+        let skipBuild = false
         if (oldChild) {
           if (isNodeString(child)) {
             if ((oldChild as NodeString).t !== child.t) {
@@ -454,11 +456,20 @@ export const build = (context: Context, node: NodeObject, children?: Child[]): v
           } else if (oldChild.tag !== child.tag) {
             node.vR.push(oldChild)
           } else {
-            oldChild.pP = oldChild.props
+            const pP = (oldChild.pP = oldChild.props)
             oldChild.props = child.props
+            oldChild.f ||= child.f || node.f
             if (typeof child.tag === 'function') {
               oldChild[DOM_STASH][2] = child[DOM_STASH][2] || []
               oldChild[DOM_STASH][3] = child[DOM_STASH][3]
+
+              if (!oldChild.f) {
+                const prevPropsKeys = Object.keys(pP)
+                const currentProps = oldChild.props
+                skipBuild =
+                  prevPropsKeys.length === Object.keys(currentProps).length &&
+                  prevPropsKeys.every((k) => k in currentProps && currentProps[k] === pP[k])
+              }
             }
             child = oldChild
           }
@@ -469,8 +480,9 @@ export const build = (context: Context, node: NodeObject, children?: Child[]): v
           }
         }
 
-        if (!isNodeString(child)) {
+        if (!isNodeString(child) && !skipBuild) {
           build(context, child)
+          delete child.f
         }
         vChildren.push(child)
 
@@ -486,6 +498,7 @@ export const build = (context: Context, node: NodeObject, children?: Child[]): v
       delete node.pC
     }
   } catch (e) {
+    node.f = true
     if (e === cancelBuild) {
       if (foundErrorHandler) {
         return
@@ -552,7 +565,9 @@ export const buildNode = (node: Child): Node | undefined => {
         tag: (node as NodeObject).tag,
         props: (node as NodeObject).props,
         key: (node as NodeObject).key,
-      })
+        f: (node as NodeObject).f,
+        // eslint-disable-next-line @typescript-eslint/no-explicit-any
+      } as any)
     }
     if (typeof (node as JSXNode).tag === 'function') {
       ;(node as NodeObject)[DOM_STASH] = [0, []]