Make flattenSubscription hooks-safe (#479)

src/ReactFinalForm.js

@@ -46,7 +46,7 @@ const ReactFinalForm = ({
   keepDirtyOnReinitialize,
   mutators,
   onSubmit,
-  subscription,
+  subscription = all,
   validate,
   validateOnBlur,
   ...rest
@@ -74,14 +74,13 @@ const ReactFinalForm = ({
       let initialState: FormState = {}
       form.subscribe(state => {
         initialState = state
-      }, subscription || all)()
+      }, subscription)()
       return initialState
     }
   )
 
-  // ⚠️ flattenedSubscription is probably not "hook-safe".
   // In the future, changing subscriptions on the fly should be banned. ⚠️
-  const flattenedSubscription = flattenSubscription(subscription || all)
+  const flattenedSubscription = flattenSubscription(subscription)
   React.useEffect(() => {
     // We have rendered, so all fields are no registered, so we can unpause validation
     form.isValidationPaused() && form.resumeValidation()
@@ -90,7 +89,7 @@ const ReactFinalForm = ({
         if (!shallowEqual(s, state)) {
           setState(s)
         }
-      }, subscription || all),
+      }, subscription),
       ...(decorators
         ? decorators.map(decorator =>
             // this noop ternary is to appease the flow gods
@@ -104,7 +103,7 @@ const ReactFinalForm = ({
       unsubscriptions.forEach(unsubscribe => unsubscribe())
     }
     // eslint-disable-next-line react-hooks/exhaustive-deps
-  }, [decorators, ...flattenedSubscription])
+  }, [decorators, flattenedSubscription])
 
   // warn about decorator changes
   // istanbul ignore next

src/flattenSubscription.js

@@ -2,6 +2,10 @@
 type Subscription = { [string]: boolean }
 export default function flattenSubscription(
   subscription: Subscription = {}
-): string[] {
-  return Object.keys(subscription).filter(key => subscription[key] === true)
+): string {
+  return Object.keys(subscription)
+    .filter(key => subscription[key] === true)
+    .map(key => key)
+    .sort()
+    .join(',')
 }

src/flattenSubscription.test.js

@@ -2,15 +2,14 @@ import flattenSubscription from './flattenSubscription'
 
 describe('flattenSubscription', () => {
   it('should return empty array when subscription is empty', () => {
-    expect(flattenSubscription(undefined)).toEqual([])
-    expect(flattenSubscription({})).toEqual([])
+    expect(flattenSubscription(undefined)).toEqual('')
+    expect(flattenSubscription({})).toEqual('')
   })
 
   it('should return only keys that are true in subscription', () => {
-    expect(flattenSubscription({ foo: true, bar: false })).toEqual(['foo'])
-    expect(flattenSubscription({ foo: true, bar: true, baz: false })).toEqual([
-      'foo',
-      'bar'
-    ])
+    expect(flattenSubscription({ foo: true, bar: false })).toEqual('foo')
+    expect(flattenSubscription({ foo: true, bar: true, baz: false })).toEqual(
+      'bar,foo'
+    )
   })
 })

src/useField.js

@@ -32,7 +32,7 @@ const useField = (
     isEqual,
     multiple,
     parse = defaultParse,
-    subscription,
+    subscription = all,
     type,
     validate,
     validateFields,
@@ -49,7 +49,7 @@ const useField = (
 
   const beforeSubmitRef = React.useRef()
   const register = (callback: FieldState => void) =>
-    form.registerField(name, callback, subscription || all, {
+    form.registerField(name, callback, subscription, {
       afterSubmit,
       beforeSubmit: () => beforeSubmitRef.current && beforeSubmitRef.current(),
       defaultValue,
@@ -82,9 +82,8 @@ const useField = (
     return beforeSubmit && beforeSubmit()
   }
 
-  // ⚠️ flattenedSubscription is probably not "hook-safe".
   // In the future, changing subscriptions on the fly should be banned. ⚠️
-  const flattenedSubscription = flattenSubscription(subscription || all)
+  const flattenedSubscription = flattenSubscription(subscription)
   React.useEffect(
     () =>
       register(state => {
@@ -105,7 +104,7 @@ const useField = (
       isEqual,
       validateFields,
       // eslint-disable-next-line react-hooks/exhaustive-deps
-      ...flattenedSubscription
+      flattenedSubscription
     ]
   )
 

src/useFormState.js

@@ -8,7 +8,7 @@ import useForm from './useForm'
 
 const useFormState = ({
   onChange,
-  subscription
+  subscription = all
 }: UseFormStateParams = {}): FormState => {
   const form: FormApi = useForm('useFormState')
   const firstRender = React.useRef(true)
@@ -19,17 +19,16 @@ const useFormState = ({
       let initialState: FormState = {}
       form.subscribe(state => {
         initialState = state
-      }, subscription || all)()
+      }, subscription)()
       if (onChange) {
         onChange(initialState)
       }
       return initialState
     }
   )
 
-  // ⚠️ flattenedSubscription is probably not "hook-safe".
   // In the future, changing subscriptions on the fly should be banned. ⚠️
-  const flattenedSubscription = flattenSubscription(subscription || all)
+  const flattenedSubscription = flattenSubscription(subscription)
   React.useEffect(
     () =>
       form.subscribe(newState => {
@@ -41,9 +40,9 @@ const useFormState = ({
             onChange(newState)
           }
         }
-      }, subscription || all),
+      }, subscription),
     // eslint-disable-next-line react-hooks/exhaustive-deps
-    flattenedSubscription
+    [flattenedSubscription]
   )
   return state
 }