feat(forms): add transformOnCommit to Form.Isolation

packages/dnb-eufemia/src/extensions/forms/DataContext/Provider/Provider.tsx

@@ -176,6 +176,10 @@ export interface Props<Data extends JsonObject> {
    * Used internally by the Form.Isolation component
    */
   isolate?: boolean
+  /**
+   * Transform the data before it gets committed to the form. The first parameter is the isolated data object. The second parameter is the outer context data object (Form.Handler).
+   */
+  transformOnCommit?: (data: Data, contextData: Data) => Data
   /**
    * The children of the context provider
    */
@@ -884,17 +888,25 @@ export default function Provider<Data extends JsonObject>(
         try {
           if (isolate) {
             const path = props.path ?? '/'
-            const data =
+            const outerData =
               props.path && pointer.has(dataNested, path)
                 ? pointer.get(dataNested, path)
                 : dataNested
+            let isolatedData = internalDataRef.current
+
+            if (typeof props.transformOnCommit === 'function') {
+              isolatedData = props.transformOnCommit(
+                isolatedData,
+                outerData
+              )
+            }
 
             // Commit the internal data to the nested context data
             handlePathChangeNested?.(
               path,
-              extendDeep({}, data, internalDataRef.current)
+              extendDeep({}, outerData, isolatedData)
             )
-            result = await onCommit?.(internalDataRef.current)
+            result = await onCommit?.(isolatedData)
           } else {
             result = await onSubmit()
           }

packages/dnb-eufemia/src/extensions/forms/Form/Isolation/Isolation.tsx

@@ -23,6 +23,13 @@ export type IsolationProps<Data> = Omit<
    */
   commitHandleRef?: React.MutableRefObject<() => void>
 
+  /**
+   * A function that will be called when the isolated context is committed.
+   * It will receive the data from the isolated context and the data from the outer context.
+   * You can use this to transform the data before it is committed.
+   */
+  transformOnCommit?: (isolatedData: Data, handlerData: Data) => Data
+
   /**
    * Will be called when the isolated context is committed.
    */

packages/dnb-eufemia/src/extensions/forms/Form/Isolation/IsolationDocs.ts

@@ -10,6 +10,11 @@ export const IsolationProperties: PropertiesTableProps = {
     type: 'string',
     status: 'optional',
   },
+  transformOnCommit: {
+    doc: 'Transform the data before it gets committed to the form. The first parameter is the isolated data object. The second parameter is the outer context data object (Form.Handler).',
+    type: 'function',
+    status: 'optional',
+  },
   commitHandleRef: {
     doc: 'Provide a ref to a function that can be called from any location to commit the data to the form.',
     type: 'React.Ref',

packages/dnb-eufemia/src/extensions/forms/Form/Isolation/__tests__/Isolation.test.tsx

@@ -1003,4 +1003,48 @@ describe('Form.Isolation', () => {
 
     expect(document.querySelectorAll('.dnb-form-status')).toHaveLength(2)
   })
+
+  it('should support "transformOnCommit"', async () => {
+    const onChange = jest.fn()
+
+    render(
+      <Form.Handler
+        data={{ existing: 'data', persons: [{ name: 'John' }] }}
+        onChange={onChange}
+      >
+        <Form.Isolation
+          transformOnCommit={(isolatedData, handlerData) => {
+            return {
+              ...handlerData,
+              persons: [...handlerData.persons, isolatedData.newPerson],
+            }
+          }}
+        >
+          <Field.String required path="/newPerson/name" />
+          <Form.Isolation.CommitButton />
+        </Form.Isolation>
+      </Form.Handler>
+    )
+
+    const commitButton = document.querySelector('button')
+    const isolated = document.querySelector('input')
+
+    await userEvent.type(isolated, 'Oda')
+    await userEvent.click(commitButton)
+
+    expect(onChange).toHaveBeenCalledTimes(1)
+    expect(onChange).toHaveBeenLastCalledWith({
+      existing: 'data',
+      persons: [{ name: 'John' }, { name: 'Oda' }],
+    })
+
+    await userEvent.type(isolated, '{Backspace>3}Odd')
+    await userEvent.click(commitButton)
+
+    expect(onChange).toHaveBeenCalledTimes(2)
+    expect(onChange).toHaveBeenLastCalledWith({
+      existing: 'data',
+      persons: [{ name: 'John' }, { name: 'Oda' }, { name: 'Odd' }],
+    })
+  })
 })