[Form lib] Fix issue where serializer on fields are called on every change

src/plugins/es_ui_shared/static/forms/hook_form_lib/components/use_field.test.tsx

@@ -17,9 +17,10 @@
  * under the License.
  */
 import React, { useEffect } from 'react';
+import { act } from 'react-dom/test-utils';
 
-import { registerTestBed } from '../shared_imports';
-import { OnUpdateHandler } from '../types';
+import { registerTestBed, TestBed } from '../shared_imports';
+import { FormHook, OnUpdateHandler, FieldConfig } from '../types';
 import { useForm } from '../hooks/use_form';
 import { Form } from './form';
 import { UseField } from './use_field';
@@ -62,4 +63,91 @@ describe('<UseField />', () => {
       lastName: 'Snow',
     });
   });
+
+  describe('serializer(), deserializer(), formatter()', () => {
+    interface MyForm {
+      name: string;
+    }
+
+    const serializer = jest.fn();
+    const deserializer = jest.fn();
+    const formatter = jest.fn();
+
+    const fieldConfig: FieldConfig = {
+      defaultValue: '',
+      serializer,
+      deserializer,
+      formatters: [formatter],
+    };
+
+    let formHook: FormHook<MyForm> | null = null;
+
+    beforeEach(() => {
+      formHook = null;
+      serializer.mockReset().mockImplementation((value) => `${value}-serialized`);
+      deserializer.mockReset().mockImplementation((value) => `${value}-deserialized`);
+      formatter.mockReset().mockImplementation((value: string) => value.toUpperCase());
+    });
+
+    const onFormHook = (_form: FormHook<MyForm>) => {
+      formHook = _form;
+    };
+
+    const TestComp = ({ onForm }: { onForm: (form: FormHook<MyForm>) => void }) => {
+      const { form } = useForm<MyForm>({ defaultValue: { name: 'John' } });
+
+      useEffect(() => {
+        onForm(form);
+      }, [form]);
+
+      return (
+        <Form form={form}>
+          <UseField path="name" config={fieldConfig} data-test-subj="myField" />
+        </Form>
+      );
+    };
+
+    test('should call each handler at expected lifecycle', async () => {
+      const setup = registerTestBed(TestComp, {
+        memoryRouter: { wrapComponent: false },
+        defaultProps: { onForm: onFormHook },
+      });
+
+      const testBed = setup() as TestBed;
+
+      if (!formHook) {
+        throw new Error(
+          `formHook is not defined. Use the onForm() prop to update the reference to the form hook.`
+        );
+      }
+
+      const { form } = testBed;
+
+      expect(deserializer).toBeCalled();
+      expect(serializer).not.toBeCalled();
+      expect(formatter).not.toBeCalled();
+
+      let formData = formHook.getFormData({ unflatten: false });
+      expect(formData.name).toEqual('John-deserialized');
+
+      await act(async () => {
+        form.setInputValue('myField', 'Mike');
+      });
+
+      expect(formatter).toBeCalled(); // Formatters are executed on each value change
+      expect(serializer).not.toBeCalled(); // Serializer are executed *only** when outputting the form data
+
+      formData = formHook.getFormData();
+      expect(serializer).toBeCalled();
+      expect(formData.name).toEqual('MIKE-serialized');
+
+      // Make sure that when we reset the form values, we don't serialize the fields
+      serializer.mockReset();
+
+      await act(async () => {
+        formHook!.reset();
+      });
+      expect(serializer).not.toBeCalled();
+    });
+  });
 });

src/plugins/es_ui_shared/static/forms/hook_form_lib/hooks/use_field.ts

@@ -118,15 +118,13 @@ export const useField = <T>(
       setIsChangingValue(true);
     }
 
-    const newValue = serializeOutput(value);
-
     // Notify listener
     if (valueChangeListener) {
-      valueChangeListener(newValue as T);
+      valueChangeListener(value);
     }
 
     // Update the form data observable
-    __updateFormDataAt(path, newValue);
+    __updateFormDataAt(path, value);
 
     // Validate field(s) and update form.isValid state
     await __validateFields(fieldsToValidateOnChange ?? [path]);
@@ -153,7 +151,6 @@ export const useField = <T>(
       }
     }
   }, [
-    serializeOutput,
     valueChangeListener,
     errorDisplayDelay,
     path,
@@ -442,13 +439,7 @@ export const useField = <T>(
 
       if (resetValue) {
         setValue(initialValue);
-        /**
-         * Having to call serializeOutput() is a current bug of the lib and will be fixed
-         * in a future PR. The serializer function should only be called when outputting
-         * the form data. If we need to continuously format the data while it changes,
-         * we need to use the field `formatter` config.
-         */
-        return serializeOutput(initialValue);
+        return initialValue;
       }
     },
     [setValue, serializeOutput, initialValue]

src/plugins/es_ui_shared/static/forms/hook_form_lib/hooks/use_form.test.tsx

@@ -22,7 +22,7 @@ import { act } from 'react-dom/test-utils';
 import { registerTestBed, getRandomString, TestBed } from '../shared_imports';
 
 import { Form, UseField } from '../components';
-import { FormSubmitHandler, OnUpdateHandler } from '../types';
+import { FormSubmitHandler, OnUpdateHandler, FormHook, ValidationFunc } from '../types';
 import { useForm } from './use_form';
 
 interface MyForm {
@@ -123,6 +123,71 @@ describe('use_form() hook', () => {
 
       expect(formData).toEqual(expectedData);
     });
+
+    test('should not build the object if the form is not valid', async () => {
+      let formHook: FormHook<MyForm> | null = null;
+
+      const onFormHook = (_form: FormHook<MyForm>) => {
+        formHook = _form;
+      };
+
+      const TestComp = ({ onForm }: { onForm: (form: FormHook<MyForm>) => void }) => {
+        const { form } = useForm<MyForm>({ defaultValue: { username: 'initialValue' } });
+        const validator: ValidationFunc = ({ value }) => {
+          if (value === 'wrongValue') {
+            return { message: 'Error on the field' };
+          }
+        };
+
+        useEffect(() => {
+          onForm(form);
+        }, [form]);
+
+        return (
+          <Form form={form}>
+            <UseField
+              path="username"
+              config={{ validations: [{ validator }] }}
+              data-test-subj="myField"
+            />
+          </Form>
+        );
+      };
+
+      const setup = registerTestBed(TestComp, {
+        defaultProps: { onForm: onFormHook },
+        memoryRouter: { wrapComponent: false },
+      });
+
+      const {
+        form: { setInputValue },
+      } = setup() as TestBed;
+
+      if (!formHook) {
+        throw new Error(
+          `formHook is not defined. Use the onForm() prop to update the reference to the form hook.`
+        );
+      }
+
+      let data;
+      let isValid;
+
+      await act(async () => {
+        ({ data, isValid } = await formHook!.submit());
+      });
+
+      expect(isValid).toBe(true);
+      expect(data).toEqual({ username: 'initialValue' });
+
+      setInputValue('myField', 'wrongValue'); // Validation will fail
+
+      await act(async () => {
+        ({ data, isValid } = await formHook!.submit());
+      });
+
+      expect(isValid).toBe(false);
+      expect(data).toEqual({}); // Don't build the object (and call the serializers()) when invalid
+    });
   });
 
   describe('form.subscribe()', () => {

src/plugins/es_ui_shared/static/forms/hook_form_lib/hooks/use_form.ts

@@ -140,7 +140,7 @@ export function useForm<T extends FormData = FormData>(
       return Object.entries(fieldsRefs.current).reduce(
         (acc, [key, field]) => ({
           ...acc,
-          [key]: field.__serializeOutput(),
+          [key]: field.value,
         }),
         {} as T
       );
@@ -233,8 +233,7 @@ export function useForm<T extends FormData = FormData>(
       fieldsRefs.current[field.path] = field;
 
       if (!{}.hasOwnProperty.call(getFormData$().value, field.path)) {
-        const fieldValue = field.__serializeOutput();
-        updateFormDataAt(field.path, fieldValue);
+        updateFormDataAt(field.path, field.value);
       }
     },
     [getFormData$, updateFormDataAt]
@@ -301,7 +300,7 @@ export function useForm<T extends FormData = FormData>(
       setSubmitting(true);
 
       const isFormValid = await validateAllFields();
-      const formData = getFormData();
+      const formData = isFormValid ? getFormData() : ({} as T);
 
       if (onSubmit) {
         await onSubmit(formData, isFormValid!);

x-pack/plugins/index_management/public/application/components/mappings_editor/components/document_fields/fields/create_field/create_field.tsx

@@ -111,14 +111,17 @@ export const CreateField = React.memo(function CreateFieldComponent({
 
       {/* Field subType (if any) */}
       <FormDataProvider pathsToWatch="type">
-        {({ type }) => (
-          <SubTypeParameter
-            key={type}
-            type={type}
-            isMultiField={isMultiField ?? false}
-            isRootLevelField={isRootLevelField}
-          />
-        )}
+        {({ type }) => {
+          const [fieldType] = type;
+          return (
+            <SubTypeParameter
+              key={fieldType.value}
+              type={fieldType.value}
+              isMultiField={isMultiField ?? false}
+              isRootLevelField={isRootLevelField}
+            />
+          );
+        }}
       </FormDataProvider>
     </EuiFlexGroup>
   );
@@ -188,7 +191,10 @@ export const CreateField = React.memo(function CreateFieldComponent({
 
             <FormDataProvider pathsToWatch={['type', 'subType']}>
               {({ type, subType }) => {
-                const ParametersForm = getParametersFormForType(type, subType);
+                const ParametersForm = getParametersFormForType(
+                  type?.[0].value,
+                  subType?.[0].value
+                );
 
                 if (!ParametersForm) {
                   return null;

x-pack/plugins/index_management/public/application/components/mappings_editor/components/document_fields/fields/edit_field/edit_field.tsx

@@ -98,15 +98,15 @@ export const EditField = React.memo(({ form, field, allFields, exitEdit, updateF
           <FormDataProvider pathsToWatch={['type', 'subType']}>
             {({ type, subType }) => {
               const linkDocumentation =
-                documentationService.getTypeDocLink(subType) ||
-                documentationService.getTypeDocLink(type);
+                documentationService.getTypeDocLink(subType?.[0].value) ||
+                documentationService.getTypeDocLink(type?.[0].value);
 
               if (!linkDocumentation) {
                 return null;
               }
 
-              const typeDefinition = TYPE_DEFINITION[type as MainType];
-              const subTypeDefinition = TYPE_DEFINITION[subType as SubType];
+              const typeDefinition = TYPE_DEFINITION[type[0].value as MainType];
+              const subTypeDefinition = TYPE_DEFINITION[subType?.[0].value as SubType];
 
               return (
                 <EuiFlexItem grow={false}>
@@ -148,7 +148,7 @@ export const EditField = React.memo(({ form, field, allFields, exitEdit, updateF
 
         <FormDataProvider pathsToWatch={['type', 'subType']}>
           {({ type, subType }) => {
-            const ParametersForm = getParametersFormForType(type, subType);
+            const ParametersForm = getParametersFormForType(type?.[0].value, subType?.[0].value);
 
             if (!ParametersForm) {
               return null;

x-pack/plugins/index_management/public/application/components/mappings_editor/components/document_fields/fields/edit_field/edit_field_header_form.tsx

@@ -36,23 +36,26 @@ export const EditFieldHeaderForm = React.memo(
 
           {/* Field subType (if any) */}
           <FormDataProvider pathsToWatch="type">
-            {({ type }) => (
-              <SubTypeParameter
-                key={type}
-                type={type}
-                defaultValueType={defaultValue.type}
-                isMultiField={isMultiField}
-                isRootLevelField={isRootLevelField}
-              />
-            )}
+            {({ type }) => {
+              const [fieldType] = type;
+              return (
+                <SubTypeParameter
+                  key={fieldType.value}
+                  type={fieldType.value}
+                  defaultValueType={defaultValue.type}
+                  isMultiField={isMultiField}
+                  isRootLevelField={isRootLevelField}
+                />
+              );
+            }}
           </FormDataProvider>
         </EuiFlexGroup>
 
         {/* Field description */}
         <FieldDescriptionSection isMultiField={isMultiField}>
           <FormDataProvider pathsToWatch={['type', 'subType']}>
             {({ type, subType }) => {
-              const typeDefinition = TYPE_DEFINITION[type as MainType];
+              const typeDefinition = TYPE_DEFINITION[type[0].value as MainType];
               const hasSubType = typeDefinition.subTypes !== undefined;
 
               if (hasSubType) {

x-pack/plugins/index_management/public/application/components/mappings_editor/reducer.ts

@@ -335,6 +335,11 @@ export const reducer = (state: State, action: Action): State => {
       return {
         ...state,
         fields: updatedFields,
+        documentFields: {
+          ...state.documentFields,
+          // If we removed the last field, show the "Create field" form
+          status: updatedFields.rootLevelFields.length === 0 ? 'creatingField' : 'idle',
+        },
         // If we have a search in progress, we reexecute the search to update our result array
         search: Boolean(state.search.term)
           ? {