fix(runtime-core): handle initial undefined attrs (#5017)

fix #5016

Author: edison1105

packages/runtime-core/__tests__/componentProps.spec.ts

@@ -573,4 +573,26 @@ describe('component props', () => {
  render(h(Comp, { foo: null }), root)
  }).not.toThrow()
  })
+
+ // #5016
+ test('handling attr with undefined value', () => {
+ const Comp = {
+ render(this: any) {
+ return JSON.stringify(this.$attrs) + Object.keys(this.$attrs)
+ }
+ }
+ const root = nodeOps.createElement('div')
+
+ let attrs: any = { foo: undefined }
+
+ render(h(Comp, attrs), root)
+ expect(serializeInner(root)).toBe(
+ JSON.stringify(attrs) + Object.keys(attrs)
+ )
+
+ render(h(Comp, (attrs = { foo: 'bar' })), root)
+ expect(serializeInner(root)).toBe(
+ JSON.stringify(attrs) + Object.keys(attrs)
+ )
+ })
 })

packages/runtime-core/src/componentProps.ts

@@ -369,7 +369,7 @@ function setFullProps(
  continue
  }
  }
- if (value !== attrs[key]) {
+ if (!(key in attrs) || value !== attrs[key]) {
  attrs[key] = value
  hasAttrsChanged = true
  }