feat(hook): add useOnFieldChange

src/hooks/__tests__/useOnFieldChange.spec.tsx

@@ -0,0 +1,113 @@
+import { ThemeProvider } from '@emotion/react'
+import { theme as lightTheme } from '@scaleway/ui'
+import { renderHook } from '@testing-library/react'
+import type { ReactElement } from 'react'
+import { CheckboxField, Form, TextBoxField } from '../../components'
+import { mockErrors } from '../../mocks'
+import { useOnFieldChange } from '../useOnFieldChange'
+
+type FormValues = {
+  textBoxName: string
+  check: boolean
+}
+
+type Wrapers = {
+  children: ReactElement
+  initialValues: FormValues
+}
+
+const initial = {
+  textBoxName: 'test',
+  check: true,
+}
+
+const updated = {
+  textBoxName: 'updated',
+  check: false,
+}
+
+const Wrapper = ({ children, initialValues }: Wrapers) => (
+  <ThemeProvider theme={lightTheme}>
+    <Form<FormValues>
+      initialValues={initialValues}
+      errors={mockErrors}
+      onRawSubmit={() => {}}
+    >
+      {children}
+      <CheckboxField name="check" />
+      <TextBoxField name="textBoxName" type="text" />
+    </Form>
+  </ThemeProvider>
+)
+
+describe('useOnFieldChange', () => {
+  test('should render correctly', () => {
+    const callback = jest.fn((value, values) => {
+      expect(value).toBe(updated.textBoxName)
+      expect(values).toBe(updated)
+    })
+
+    let initialValues = initial
+
+    const { result, rerender } = renderHook(
+      () =>
+        useOnFieldChange<FormValues['textBoxName'], FormValues>(
+          'textBoxName',
+          // Condition always true, just need to change a value inside the form to trigger this hook
+          true,
+          callback,
+        ),
+      {
+        wrapper: ({ children }) => (
+          <Wrapper initialValues={initialValues}>{children}</Wrapper>
+        ),
+      },
+    )
+
+    expect(result.current).toBeUndefined()
+
+    expect(callback).toHaveBeenCalledTimes(0)
+
+    initialValues = updated
+
+    rerender()
+
+    expect(callback).toHaveBeenCalledTimes(1)
+  })
+
+  test('should render when condition change', () => {
+    const callback = jest.fn()
+
+    let initialValues = initial
+
+    const { result, rerender } = renderHook(
+      ({ condition }) => {
+        useOnFieldChange<FormValues['textBoxName'], FormValues>(
+          'textBoxName',
+          // Condition will depends of rerender({ condition: '' })
+          condition,
+          callback,
+        )
+      },
+      {
+        wrapper: ({ children }) => (
+          <Wrapper initialValues={initialValues}>{children}</Wrapper>
+        ),
+
+        initialProps: {
+          condition: false,
+        },
+      },
+    )
+
+    expect(result.current).toBeUndefined()
+
+    expect(callback).toHaveBeenCalledTimes(0)
+
+    initialValues = updated
+
+    rerender({ condition: true })
+
+    expect(callback).toHaveBeenCalledTimes(1)
+  })
+})

src/hooks/index.ts

@@ -1,2 +1,3 @@
 export { useValidation } from './useValidation'
 export { useFormField } from './useFormField'
+export { useOnFieldChange } from './useOnFieldChange'

src/hooks/useOnFieldChange.ts

@@ -0,0 +1,29 @@
+import { useEffect, useRef } from 'react'
+import { useField, useFormState } from 'react-final-form'
+
+type CallbackFn<FieldValue, AllValues> = (
+  value: FieldValue,
+  values: AllValues,
+) => unknown
+
+export const useOnFieldChange = <FieldValue = unknown, AllValues = unknown>(
+  name: string,
+  condition: boolean,
+  callback: CallbackFn<FieldValue, AllValues>,
+): void => {
+  const { values } = useFormState<AllValues>()
+  const {
+    input: { value },
+  } = useField<FieldValue>(name, {
+    allowNull: true,
+    subscription: { value: true },
+  })
+  const previousValues = useRef(value)
+
+  useEffect(() => {
+    if (previousValues.current !== value && condition) {
+      previousValues.current = value
+      callback(value, values)
+    }
+  }, [value, values, callback, condition])
+}

src/index.ts

@@ -17,7 +17,7 @@ export {
   TimeField,
   ToggleField,
 } from './components'
-export { useValidation } from './hooks'
+export { useValidation, useOnFieldChange } from './hooks'
 export type { BaseFieldProps, FormErrors } from './types'
 export { pickValidators } from './helpers'
 export { useErrors, ErrorProvider } from './providers/ErrorContext'