easier resolution of types

Signed-off-by: Paul Cowan <paul.cowan@cutting.scot>

plugins/scaffolder/src/components/MultistepJsonForm/MultistepJsonForm.tsx

@@ -36,6 +36,7 @@ import { transformSchemaToProps } from './schema';
 import { Content, StructuredMetadataTable } from '@backstage/core-components';
 import cloneDeep from 'lodash/cloneDeep';
 import * as fieldOverrides from './FieldOverrides';
+import { LayoutOptions, resolveStepLayout } from '../../layouts';
 
 const Form = withTheme(MuiTheme);
 type Step = {

plugins/scaffolder/src/layouts/index.tsx

@@ -15,21 +15,23 @@
  */
 
 import { attachComponentData, Extension } from '@backstage/core-plugin-api';
-import { UiSchema } from '@rjsf/core';
-import { DEFAULT_SCAFFOLDER_LAYOUT } from './default';
+import { ObjectFieldTemplateProps } from '@rjsf/core';
 import type { LayoutOptions, ObjectFieldTemplate } from './types';
 
 export const LAYOUTS_KEY = 'scaffolder.layout.v1';
 export const LAYOUTS_WRAPPER_KEY = 'scaffolder.layouts.wrapper.v1';
 
-export type LayoutComponent<_TReturnValue, _TInputProps> = () => null;
+type LayoutComponent<_TInputProps> = () => null;
 
-export function createScaffolderLayout<
-  TFieldReturnValue = unknown,
-  TInputProps = unknown,
->(
+type GetProps<T> = T extends LayoutOptions
+  ? T['component'] extends ObjectFieldTemplate<infer P>
+    ? LayoutComponent<ObjectFieldTemplateProps<P>>
+    : never
+  : never;
+
+export function createScaffolderLayout(
   options: LayoutOptions,
-): Extension<LayoutComponent<TFieldReturnValue, TInputProps>> {
+): Extension<GetProps<typeof options>> {
   return {
     expose() {
       const LayoutDataHolder: any = () => null;
@@ -50,22 +52,4 @@ export type { LayoutOptions, ObjectFieldTemplate } from './types';
 
 export { DEFAULT_SCAFFOLDER_LAYOUT } from './default';
 
-export function resolveStepLayout(
-  uiSchema: UiSchema = {},
-  layouts: LayoutOptions[],
-): ObjectFieldTemplate {
-  const layoutName =
-    uiSchema?.['ui:ObjectFieldTemplate'] ?? DEFAULT_SCAFFOLDER_LAYOUT.name;
-
-  delete uiSchema?.['ui:ObjectFieldTemplate'];
-
-  const LayoutComponent = layouts.find(
-    layout => layout.name === layoutName,
-  )?.component;
-
-  if (!LayoutComponent) {
-    throw new Error(`no step layout found for ${layoutName}`);
-  }
-
-  return LayoutComponent;
-}
+export { resolveStepLayout } from './resolveStepLayout';

plugins/scaffolder/src/layouts/resolveStepLayout.ts

@@ -0,0 +1,39 @@
+/*
+ * Copyright 2022 The Backstage Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import { UiSchema } from '@rjsf/core';
+import { DEFAULT_SCAFFOLDER_LAYOUT } from './default';
+import { LayoutOptions, ObjectFieldTemplate } from './types';
+
+export function resolveStepLayout(
+  uiSchema: UiSchema = {},
+  layouts: LayoutOptions[],
+): ObjectFieldTemplate {
+  const layoutName =
+    uiSchema?.['ui:ObjectFieldTemplate'] ?? DEFAULT_SCAFFOLDER_LAYOUT.name;
+
+  delete uiSchema?.['ui:ObjectFieldTemplate'];
+
+  const LayoutComponent = layouts.find(
+    layout => layout.name === layoutName,
+  )?.component;
+
+  if (!LayoutComponent) {
+    throw new Error(`no step layout found for ${layoutName}`);
+  }
+
+  return LayoutComponent;
+}

plugins/scaffolder/src/layouts/types.ts

@@ -13,13 +13,13 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-import type { FormProps } from '@rjsf/core';
+import type { ObjectFieldTemplateProps } from '@rjsf/core';
 
-export type ObjectFieldTemplate = Required<
-  FormProps<any>
->['ObjectFieldTemplate'];
+export type ObjectFieldTemplate<P = any> = (
+  c: ObjectFieldTemplateProps<P>,
+) => JSX.Element;
 
-export interface LayoutOptions {
+export interface LayoutOptions<P = any> {
   name: string;
-  component: ObjectFieldTemplate;
+  component: ObjectFieldTemplate<P>;
 }