Fix #3948 - Changing state was also causing change of initial value

.changeset/empty-vans-bathe.md

@@ -0,0 +1,5 @@
+---
+'formik': patch
+---
+
+Changing the state inside formik was changing reference of initialValues provided via props, deep cloning the initialvalues will fix it.

packages/formik/src/Formik.tsx

@@ -1,5 +1,6 @@
 import deepmerge from 'deepmerge';
 import isPlainObject from 'lodash/isPlainObject';
+import cloneDeep from 'lodash/cloneDeep';
 import * as React from 'react';
 import isEqual from 'react-fast-compare';
 import invariant from 'tiny-warning';
@@ -173,10 +174,10 @@ export function useFormik<Values extends FormikValues = FormikValues>({
 
   const [, setIteration] = React.useState(0);
   const stateRef = React.useRef<FormikState<Values>>({
-    values: props.initialValues,
-    errors: props.initialErrors || emptyErrors,
-    touched: props.initialTouched || emptyTouched,
-    status: props.initialStatus,
+    values: cloneDeep(props.initialValues),
+    errors: cloneDeep(props.initialErrors) || emptyErrors,
+    touched: cloneDeep(props.initialTouched) || emptyTouched,
+    status: cloneDeep(props.initialStatus),
     isSubmitting: false,
     isValidating: false,
     submitCount: 0,

packages/formik/test/Formik.test.tsx

@@ -61,6 +61,20 @@ const InitialValues = {
   age: 30,
 };
 
+const InitialValuesWithNestedObject = {
+  content: {
+    items: [
+      {
+        cards: [
+          {
+            desc: 'Initial Desc',
+          },
+        ],
+      },
+    ],
+  },
+};
+
 function renderFormik<V extends FormikValues = Values>(
   props?: Partial<FormikConfig<V>>
 ) {
@@ -1454,4 +1468,34 @@ describe('<Formik>', () => {
 
     expect(innerRef.current).toEqual(getProps());
   });
+
+  it('should not modify original initialValues object', () => {
+    render(
+      <Formik initialValues={InitialValuesWithNestedObject} onSubmit={noop}>
+        {formikProps => (
+          <input
+            data-testid="desc-input"
+            value={formikProps.values.content.items[0].cards[0].desc}
+            onChange={e => {
+              const copy = { ...formikProps.values.content };
+              copy.items[0].cards[0].desc = e.target.value;
+              formikProps.setValues({
+                ...formikProps.values,
+                content: copy,
+              });
+            }}
+          />
+        )}
+      </Formik>
+    );
+    const input = screen.getByTestId('desc-input');
+
+    fireEvent.change(input, {
+      target: {
+        value: 'New Value',
+      },
+    });
+
+    expect(InitialValuesWithNestedObject.content.items[0].cards[0].desc).toEqual('Initial Desc');
+  });
 });