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Experimental: Testing out the alpha Scaffolder plugin

What's scaffolder/next?​

The alpha version, or as you might have seen referred to in other places the scaffolder/next release, is a new version of the scaffolder plugin that will be the first breaking change to the plugin, so you can also think of it as @backstage/plugin-scaffolder@2.0.0. Its mostly a rewrite of a lot of the frontend components and pages that had very limited test coverage, which made adding new features to the scaffolder plugin quite hard, and we were lacking in confidence when making changes.

There is of course some other things that have changed when re-writing this, which are essentially what has caused some breaking changes. Now, this is not like previous scaffolder changes where you would have to change all of your templates as this is only the frontend plugin that is going to have breaking changes. You can read more about the breaking changes below.

What's new?​

First off, the main dependency that we have for the frontend which is responsible for rendering the JSONSchema into material-ui components is react-jsonschema-form. This dependency in the current version of the plugin is 3.x.x, which is now 2 major versions out of date. Long story short, v4 of this plugin contained some bug fixes, and new features but we we're unable to upgrade due to some issues with having support for material-ui@v4, so we had to wait for v5 to be released, and because of the FieldExtensions and how they are very tightly coupled to the react-jsonschema-form library, we also wanted to make sure that this release was stable before getting people to migrate their Field Extensions.

With that in mind, this release has v5 of react-jsonschema-form, and with that comes all the new features and bugfixes in v4 that we were waiting for - one of the main ones being the ability to use if / then / else syntax in the template.yaml definitions! 🎉

We've also rebuilt how validation works in the scaffolder components, which now means that we've opened the ability to have async validation functions in your Field Extensions.

Some of the pages have gotten a little bit of an overhaul in terms of UI based on some research and feedback from the community and internally.

  • The TemplateList page has gotten some new Card components which show a little more information than the previous version with a little material-ui standards.
  • The WizardPage has received some new updates with the stepper now running horizontally, and the Review step being a dedicated step in the stepper.
  • The OngoingTask page now does not show the logs by default, and instead has a much cleaner interface for tracking the ongoing steps and the pipeline of actions that are currently showing.
    • You can also now provide your own OutputsComponent which can be used to render the outputs from an ongoing / completed task in a way that suits your templates the best. For instance, if your template produces Pull Requests, it could be useful to render these in an interactive way where you can see the statuses of each of these Pull Requests in the Ongoing Task page.

There's also a lot of bug fixes, and other things, but these are the main ones that we wanted to highlight.

How do I test out the alpha version?​

With the release of v1.11.0 it's now possible to run the scaffolder/next plugin and it be a drop in replacement for the current version that you use today. This means that you can start using the new code, and start testing it out. Once we have collected enough feedback, and squashed any bugs that might block us from releasing, it will be promoted from the /alpha exports and replace the existing code leading to breaking changes if you haven't already made these changes as part of this testing pilot. Those that have chosen to opt into this testing pilot means that once we promote it from the /alpha exports, you will need to update your code to point to the original exports from the scaffolder plugin, just like the code is today but with the breaking changes that you already made to your Custom Field Extensions.

It's also worth calling out that if you do test this out, and find some issues or something not working out as expected, feel free to raise an issue in the repo or reach out to us on Discord!

Make the required changes to App.tsx​

The ScaffolderPage router has a completely different export for the scaffolder/next work, so you will want to change any import from the old ScaffolderPage to the new NextScaffolderPage

import { ScaffolderPage } from '@backstage/plugin-scaffolder';
import { NextScaffolderPage } from '@backstage/plugin-scaffolder/alpha';

And this API should be the exact same as the previous Router, so you should be able to make a change like the following further down in this file:

<Route
  path="/create"
  element={
    <ScaffolderPage
    <NextScaffolderPage
      groups={[
        {
          title: 'Recommended',
          filter: entity =>
            entity?.metadata?.tags?.includes('recommended') ?? false,
        },
      ]}
    />
  }
>
  <ScaffolderFieldExtensions>
    <LowerCaseValuePickerFieldExtension />
    {/* ... other extensions */}
  </ScaffolderFieldExtensions>
  <ScaffolderLayouts>
    <TwoColumnLayout />
    {/* ... other layouts */}
  </ScaffolderLayouts>
</Route>

Optionally, you can choose to run the two side by side by using FeatureFlags in your App.tsx if you wish, but, we would also recommend duplicating any CustomFieldExtensions too as the new CustomFieldExtensions might not be compatible with the old form.

<FeatureFlagged with="scaffolder-next-preview">
  <Route path="/create" element={<NextScaffolderPage />}>
    <ScaffolderFieldExtensions>
      <DelayingComponentFieldExtension />
    </ScaffolderFieldExtensions>
  </Route>
</FeatureFlagged>
<FeatureFlagged without="scaffolder-next-preview">
  <Route path="/create" element={<ScaffolderPage />}>
    <ScaffolderFieldExtensions>
      <DelayingComponentFieldExtension />
    </ScaffolderFieldExtensions>
  </Route>
</FeatureFlagged>

You should then be able to enable the scaffolder-next-preview feature flag under /settings/feature-flags in Backstage.

Make the required changes to your CustomFieldExtensions​

There's differently named function for creating field extensions part of the /alpha exports as these are the ones that can contain breaking changes because of the breaking changes that have been applied in react-jsonschema-form.

Let's take the following example:

export const EntityNamePickerFieldExtension = scaffolderPlugin.provide(
  createScaffolderFieldExtension({
    component: EntityNamePicker,
    name: 'EntityNamePicker',
    validation: entityNamePickerValidation,
    schema: EntityNamePickerSchema,
  }),
);

References for createScaffolderFieldExtension have an /alpha version of createNextScaffolderFieldExtension, which should be used instead.

import { createScaffolderFieldExtension } from '@backstage/plugin-scaffolder';
import { createNextScaffolderFieldExtension } from '@backstage/plugin-scaffolder-react/alpha';

export const EntityNamePickerFieldExtension = scaffolderPlugin.provide(
  createScaffolderFieldExtension({
  createNextScaffolderFieldExtension({
    component: EntityNamePicker,
    name: 'EntityNamePicker',
    validation: entityNamePickerValidation,
  }),
);

Once you've done this you will find that you will have two squiggly lines under the properties that are passed in. One for the component and one for the validation (if provided.)

Let's take the following code for the EntityNamePicker component:

export const EntityNamePicker = (
  props: FieldExtensionComponentProps<string, EntityNamePickerProps>,
) => {
  const {
    onChange,
    required,
    schema: { title = 'Name', description = 'Unique name of the component' },
    rawErrors,
    formData,
    uiSchema: { 'ui:autofocus': autoFocus },
    idSchema,
    placeholder,
  } = props;
  // ..
};

There's another /alpha export that you need to replace FieldExtensionComponentProps with which is the NextFieldExtensionComponentProps.

import { FieldExtensionComponentProps } from '@backstage/plugin-scaffolder-react';
import { NextFieldExtensionComponentProps } from '@backstage/plugin-scaffolder-react/alpha';

export const EntityNamePicker = (
  props: FieldExtensionComponentProps<string, EntityNamePickerProps>,
  props: NextFieldExtensionComponentProps<string, EntityNamePickerProps>,
) => {
  const {
    onChange,
    required,
    schema: { title = 'Name', description = 'Unique name of the component' },
    rawErrors,
    formData,
    uiSchema: { 'ui:autofocus': autoFocus },
    uiSchema: { 'ui:autofocus': autoFocus } = {},
    idSchema,
    placeholder,
  } = props;
  // ..
};

You'll notice that there's an additional change here, which is that we're now defaulting the uiSchema to an empty object. This is because the uiSchema is now optional, and if you don't provide it, it will be undefined instead of an empty object. There's more around this in the breaking changes section.

To fix the previous validation error, you will need to change the import for the FieldValidation type that is used in the validation function.

Let's take the following example of the validation function:

import { FieldValidation } from '@rjsf/utils';
import { KubernetesValidatorFunctions } from '@backstage/catalog-model';

export const entityNamePickerValidation = (
  value: string,
  validation: FieldValidation,
) => {
  if (!KubernetesValidatorFunctions.isValidObjectName(value)) {
    validation.addError(
      'Must start and end with an alphanumeric character, and contain only alphanumeric characters, hyphens, underscores, and periods. Maximum length is 63 characters.',
    );
  }
};

You will need to change the import for FieldValidation to point at the new react-jsonschema-form dependency.

Note: you will probably need to install this dependency too, by using yarn add @rjsf/utils in the package where you define these validation functions, this could also be in the packages/app folder, so you can install it there if needed.

import { FieldValidation } from '@rjsf/core';
import { FieldValidation } from '@rjsf/utils;
import { KubernetesValidatorFunctions } from '@backstage/catalog-model';

export const entityNamePickerValidation = (
  value: string,
  validation: FieldValidation,
) => {

Breaking Changes​

Once we fully release the code that is in the /alpha exports right now onto the current API and release v2.0.0 of @backstage/plugin-scaffolder the breaking changes will be as follows:

uiSchema is now optional​

Later releases of react-jsonschema-form have made the uiSchema optional, and if you don't provide it, it will be undefined instead of an empty object. This means that you will need to make sure that you're defaulting the uiSchema to an empty object if you're using it in your code.

const {
  onChange,
  required,
  schema: { title = 'Name', description = 'Unique name of the component' },
  rawErrors,
  formData,
  uiSchema: { 'ui:autofocus': autoFocus },
  uiSchema: { 'ui:autofocus': autoFocus } = {},
  idSchema,
  placeholder,
} = props;
// ..

formData can also be undefined​

If you were using the formData and assuming that it was set to an empty object when building Field Extensions that return objects, then this will be undefined now due to a change in the react-jsonschema-form library.

const {
  onChange,
  required,
  schema: { title = 'Name', description = 'Unique name of the component' },
  rawErrors,
  formData,
  formData = {}, // or maybe some other default value that you would prefer
  uiSchema: { 'ui:autofocus': autoFocus } = {},
  idSchema,
  placeholder,
} = props;
// ..