Improve and fix types of value in useFieldArray

README.md

@@ -296,9 +296,9 @@ Updates a value of the specified index of the array field.
 
 A function to add a value to the beginning of the array.
 
-#### `fields.value: any[]`
+#### `fields.value: void | any[]`
 
-The value of the array. Should be treated as readonly.
+The value of the field. Should be treated as readonly.
 
 #### `meta.active?: boolean`
 

src/index.d.ts

@@ -16,7 +16,7 @@ export interface FieldArrayRenderProps<FieldValue, T extends HTMLElement> {
     shift: () => FieldValue
     swap: (indexA: number, indexB: number) => void
     unshift: (value: FieldValue) => void
-    value: FieldValue[]
+    value: void | FieldValue[]
   } & FieldState<FieldValue[]>
   meta: Partial<{
     // TODO: Make a diff of `FieldState` without all the functions

src/index.js.flow

@@ -9,6 +9,6 @@ import type {
 declare export var FieldArray: React.ComponentType<FieldArrayProps>
 declare export var useFieldArray: (
   name: string,
-  config: UseFieldArrayConfig
+  config?: UseFieldArrayConfig
 ) => FieldArrayRenderProps
 declare export var version: string

src/types.js.flow

@@ -35,7 +35,7 @@ export type FieldArrayRenderProps = {
     shift: () => any,
     swap: (indexA: number, indexB: number) => void,
     unshift: (value: any) => void,
-    value: any[]
+    value: void | any[]
   },
   meta: Meta
 }

src/useFieldArray.test.js

@@ -58,4 +58,44 @@ describe('FieldArray', () => {
     expect(spy).toHaveBeenCalledTimes(2)
     expect(spy.mock.calls[1][0].fields.length).toBe(1)
   })
+
+  it('should have undefined as value when not initialized', () => {
+    const spy = jest.fn()
+    const MyFieldArray = () => {
+      spy(useFieldArray('names'))
+      return null
+    }
+    render(
+      <Form onSubmit={onSubmitMock} mutators={arrayMutators} subscription={{}}>
+        {() => (
+          <form>
+            <MyFieldArray />
+          </form>
+        )}
+      </Form>
+    )
+    expect(spy).toHaveBeenCalled()
+    expect(spy).toHaveBeenCalledTimes(1)
+    expect(spy.mock.calls[0][0].fields.value).toEqual(undefined)
+  })
+
+  it('should have empty array as value when initialized', () => {
+    const spy = jest.fn()
+    const MyFieldArray = () => {
+      spy(useFieldArray('names', { initialValue: [] }))
+      return null
+    }
+    render(
+      <Form onSubmit={onSubmitMock} mutators={arrayMutators} subscription={{}}>
+        {() => (
+          <form>
+            <MyFieldArray />
+          </form>
+        )}
+      </Form>
+    )
+    expect(spy).toHaveBeenCalled()
+    expect(spy).toHaveBeenCalledTimes(1)
+    expect(spy.mock.calls[0][0].fields.value).toEqual([])
+  })
 })