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@apostrophecms/apostrophe-astro

Astro integration for ApostropheCMS

This module integrates ApostropheCMS into your Astro application.

About Astro

Astro provides a "universal bridge" to run modern frontend frameworks like React, Vue, and SvelteJS on the server side, as well as a straightforward, JSX-like template language of its own to meld everything together.

Bringing ApostropheCMS and Astro together

The intent of this integration is to let Apostrophe manage content, handle routing of URLs and fetch content, and let Astro take the responsibility for the rendering of pages and any associated logic using your framework(s) of choice like React, Vue.js, Svelte, etc. (see the Astro integrations page for more).

This module also brings the ApostropheCMS Admin UI in your Astro application, so you can manage your site exactly as if you were in a "normal" Apostrophe instance.

When you use this module, you will have two projects:

  1. An Astro project. This is where you write your templates and frontend code. As a starting point, we recommend forking our apostrophecms/astro-frontend project.

  2. An Apostrophe project. This is where you define your page types, widget types and other content types with their schemas and other customizations. As a starting point, we recommend forking our apostrophecms/starter-kit-astro project, or creating a new project from it using our CLI:

apos create my-apos-project-name --starter=astro

This kind of dual-project CMS integration is typical for Astro.

Note that this module, @apostrophecms/apostrophe-astro, is meant to be installed as a dependency of the Astro project, not the Apostrophe project.

This module is currently designed for use with Astro's output: 'server' setting (SSR mode), so that you can edit your content directly on the page. Support for export as a static site is under consideration for the future.

Installation

If you did not fork the sample projects above, you will need to install this module into your Astro project. Install this module in your Astro project, not your ApostropheCMS project:

cd my-astro-project
npm install @apostrophecms/apostrophe-astro

Astro 3.x and 4.x are both supported.

Security

You must set the APOS_EXTERNAL_FRONT_KEY environment variable to a secret value when running your Astro project, and also set the same variable to the same value when running your Apostrophe application. This ensures that other sites on the web cannot fetch excessive amounts of information from ApostropheCMS without your permission.

Configuration (Astro)

Since this is an Astro integration, you will need to add it to your Astro project's astro.config.mjs file. Here is a working astro.config.js file for a project with an Apostrophe CMS backend.

import { defineConfig } from 'astro/config';
import apostrophe from '@apostrophecms/apostrophe-astro';

// For production. You can use other adapters that support
// `output: 'server'`
import node from '@astrojs/node';

export default defineConfig({
  output: 'server',
  adapter: node({
    mode: 'standalone'
  }),
  integrations: [
    apostrophe({
      aposHost: 'http://localhost:3000',
      widgetsMapping: './src/widgets',
      templatesMapping: './src/templates',
      viewTransitionWorkaround: false,
      forwardHeaders: [
        'content-security-policy', 
        'strict-transport-security', 
        'x-frame-options',
        'referrer-policy',
        'cache-control',
        'host'
      ],
      proxyRoutes: [
        // Custom URLs that should be proxied to Apostrophe.
        // Note that all of `/api/v1` is already proxied, so
        // this is usually unnecessary
      ]
    })
  ],
  vite: {
    ssr: {
      // Do not externalize the @apostrophecms/apostrophe-astro plugin, we need
      // to be able to use virtual: URLs there
      noExternal: [ '@apostrophecms/apostrophe-astro' ],
    }
  }
});

Options

aposHost (mandatory)

This option is the base URL of your Apostrophe instance. It must contain the port number if testing locally and/or communicating directly with another instance on the same server in a small production deployment. This option can be overriden at runtime with the APOS_HOST environment variable.

During development it defaults automatically to: http://localhost:3000

widgetsMapping (mandatory)

The file in your project that contains the mapping between Apostrophe widget types and your Astro components (see below).

templatesMapping (mandatory)

The file in your project that contains the mapping between Apostrophe templates and your Astro templates (see below).

viewTransitionWorkaround (optional)

If set to true, Apostrophe will refresh its admin UI JavaScript on every page transition, to ensure compatibility with Astro view transitions. If you are not using this feature of Astro, you can omit this flag to improve performance for editors. Ordinary website visitors are not impacted in any case. We are seeking an alternative solution to eliminate this option.

forwardHeaders

An array of HTTP headers that you want to forward from Apostrophe to the final response sent to the browser - useful if you want to use an Apostrophe module like @apostrophecms/security-headers and want to keep those headers as configured in Apostrophe.
At the present time, Astro is not compatible with the nonce property of content-security-policy script-src value. So this is automatically removed with that integration. The rest of the CSP header remains unchanged.

Mapping Apostrophe templates to Astro components

Since the front end of our project is entirely Astro, we'll need to create Astro components corresponding to each template that Apostrophe would normally render with Nunjucks.

Create your template mapping in src/templates/index.js file.
As shown above, this file path must then be added to your astro.config.mjs file, in the templatesMapping option of the apostrophe integration.

// src/templates/index.js
import HomePage from './HomePage.astro';
import DefaultPage from './DefaultPage.astro';
import BlogIndexPage from './BlogIndexPage.astro';
import BlogShowPage from './BlogShowPage.astro';
import NotFoundPage from './NotFoundPage.astro';

const templateComponents = {
  '@apostrophecms/home-page': HomePage,
  'default-page': DefaultPage,
  '@apostrophecms/blog-page:index': BlogIndexPage,
  '@apostrophecms/blog-page:show': BlogShowPage,
  '@apostrophecms/page:notFound': NotFoundPage
};

export default templateComponents;

How Apostrophe template names work

For ordinary page templates, like the home page or a typical "default" page type in an Apostrophe project, you can just specify the Apostrophe module name.

For special templates like notFound, and for modules that serve more than one template, you'll need to specify the complete name. For instance, Apostrophe's @apostrophecms/blog module contains an @apostrophecms/blog-page page type that renders an index template when viewing the main page of the blog, and a show template when viewing a single blog post (a "permalink" page).

If you don't specify the template name, :page is assumed, which is just right for ordinary page types.

For the "404 Not Found" page, use @apostrophecms/page:notFound, which is the standard name for this template in ApostropheCMS.

Special template names

The integration comes with two additional special template names that can be mapped to Astro templates. You should not add a module name to these special names:

  • apos-fetch-error: served when Apostrophe generates a 500-class error. The integration will set Astro's response status to 500.
  • apos-no-template: served when there is no mapping corresponding to the Apostrophe page type for this page.

See below for an example Astro template for the @apostrophe-cms/home-page type. But first, let's look at widgets.

Mapping Apostrophe widgets to Astro components

Similar to Astro page components, Astro widget components replace Apostrophe's usual widget rendering.

Create your template mapping in a file in your application, for example in a src/widgets/index.js file. This file path must then be added to your astro.config.mjs file, in the widgetsMapping option of the apostrophe integration, as seen above.

// src/widgets/index.js

import RichTextWidget from './RichTextWidget.astro';
import ImageWidget from './ImageWidget.astro';
import VideoWidget from './VideoWidget.astro';
import TwoColumnWidget from './TwoColumnWidget.astro';

const widgetComponents = {
  // Standard widgets, but we must provide our own Astro components for them
  '@apostrophecms/rich-text': RichTextWidget,
  '@apostrophecms/image': ImageWidget,
  '@apostrophecms/video': VideoWidget,
  // Project-level widget
  'two-column': TwoColumnWidget
};

export default widgetComponents;

Note that even basic widget types like @apostrophecms/image do need an Astro template in your project. This integration does not currently ship with built-in Astro templates for all of the common Apostrophe widgets. However, see the provided astro frontend starter project for examples of several of these.

Note that the Apostrophe widget name (on the left) is the name of your widget module without the -widget part.

The naming of your Astro widget templates is up to you. The above convention is just a suggestion.

Creating the [...slug.astro] component and fetching Apostrophe data

Since Apostrophe is responsible for managing URLs to content, including creating new content and pages on the fly, you will only need one top-level Astro page component: the [...slug].astro route.

The integration comes with an aposPageFetch method that can be used to automatically fetch the relevant data for the current URL.

Your [...slug].astro component should look like this:

---
import aposPageFetch from '@apostrophecms/apostrophe-astro/lib/aposPageFetch.js';
import AposLayout from '@apostrophecms/apostrophe-astro/components/layouts/AposLayout.astro';
import AposTemplate from '@apostrophecms/apostrophe-astro/components/AposTemplate.astro';

const aposData = await aposPageFetch(Astro.request);
const bodyClass = `myclass`;

if (aposData.redirect) {
  return Astro.redirect(aposData.url, aposData.status);
}
if (aposData.notFound) {
  Astro.response.status = 404;
}
---
<AposLayout title={aposData.page?.title} {aposData} {bodyClass}>
    <Fragment slot="standardHead">
      <meta name="description" content={aposData.page?.seoDescription} />
      <meta name="viewport" content="width=device-width, initial-scale=1" />
      <meta charset="UTF-8" />
    </Fragment>
    <AposTemplate {aposData} slot="main" />
</AposLayout>

Thanks to the aposPageFetch call, the aposData object will then contain all of the information normally provided by data in an ApostropheCMS Nunjucks template. This includes, but is not limited to:

  • page: the page document for the current URL, if any
  • piece: the piece document when on a "show page" for a piece page type
  • pieces: an array of pieces when on an "index page" for a piece page type
  • user: information about the currently logged-in user
  • global: the ApostropheCMS global document e.g. global settings, editable global headers and footers, etc.
  • query: the req.query object, giving access to query parameters in the URL.

Any other data that your custom Apostrophe code attaches to req.data is also available here.

Understanding AposLayout

This integration comes with a full managed global layout, replacing the outerLayout.html used in Nunjucks page templates.

In your [...slug].astro file, use the AposLayout component built into this integration to leverage the global layout.

To override any aspect of the global layout, take advantage of the following Astro slots, which are closely related to what ApostropheCMS offers in Nunjucks:

  • startHead: slot in the very beginning of the <head>
  • standardHead: slot in the middle of <head>, just after <title>
  • extraHead: still in the HTML <head>, at the very end
  • startBody: at the very beginning of the <body> - this is not part of the refresh zone in edit mode
  • beforeMain: at the very beginning of the main body zone - part of the refresh zone in edit mode
  • main: the inner part of the main body zone - part of the refresh zone in edit mode
  • afterMain: at the very end of the main body zone - part of the refresh zone in edit mode
  • endBody: at the very end of the <body> - this is not part of the refresh zone in edit mode

In addition, the AposLayout component expects four props:

  • aposData: the data fetched from Apostrophe
  • title: this will go in the <title> HTML tag
  • lang which will be set in the <html> lang attribute
  • bodyClass: this will be added in the class attribute of the <body> element

This layout component will automatically manage the switch between support for the editing UI if a user is logged in and a simpler "Run Layout" for all other page requests.

Understanding AposTemplate

The role of AposTemplate is to automatically find the right Astro component to render based on the template mapping you created earlier. It accepts one prop, the full aposData object.

Creating Astro page components

Next we'll look at how to write Astro page components, such as the src/templates/HomePage.astro file mentioned above.

We do not recommend placing these in src/pages because their names are not routes and Astro should not try to compile them as routes. Place them in src/templates instead. src/pages should only contain the [...slug.astro] file.

As an example, let's take a look at a simple home page template:

---
// src/templates/HomePage.astro
import AposArea from '@apostrophecms/apostrophe-astro/components/AposArea.astro';
const { page } = Astro.props.aposData;
const { main } = page;
---

<section>
  <h1>{ page.title }</h>
  <AposArea area={main} />
</section>

Notice that we receive the page object from Apostrophe, which gives us access to page.title. This is similar to data.page in a Nunjucks template.

Understanding the AposArea component

This component allows Astro to render Apostrophe areas, and provides a standard Apostrophe editing experience when doing so. Astro will automatically call our widget components once content exists in the area. All we have to do is pass on the area object, in this case the main schema field of page.

Note that we can also pass area objects that are schema fields of widgets. This allows for nested widgets, such as multiple-column widgets often used for page layout.

Note that additional props can be passed to the AposArea component and will be made accessible to widget components.

Creating Astro widget components

Earlier we created a mapping from Apostrophe widget names to Astro components. Let's take a look at how to implement these.

You Astro widget will receive a widget property, in addition to any custom props you passed to the AposArea component. This widget property contains the the schema fields of your Apostrophe widget.

As an example, here is a simple Astro component to render @apostrophecms/image widgets:

---
const { widget } = Astro.props;
const placeholder = widget?.aposPlaceholder;
const src = placeholder ?
  '/images/image-widget-placeholder.jpg' :
  widget?._image[0]?.attachment?._urls['full'];
---
<style>
  .img-widget {
    width: 100%;
  }
</style>
<img class="img-widget" {src} />

Placeholders are important in widgets that use them

Why are we checking for aposPlaceholder? Apostrophe's @apostrophecms/image widget displays a placeholder image until the user clicks the edit pencil to select their image of choice. When rendered by Astro, Apostrophe still expects this to be the case. So we need to provide our own placeholder rendering.

In this case, a suitably named file must exist in public/images in our Astro project.

Remember, relationship properties might not be populated

It is always possible that the image associated with an image widget has been archived. The ?. syntax is a simple way to avoid a 500 error in such a situation. You may wish to add a more sophisticated fallback.

Accessing image and URLs

Properties like .attachment._urls['full'] exist on all image pieces, while properties like .attachment._url exist on non-image attachments such as PDFs. For more information, see the attachment field format.

What to change in your Apostrophe project

Nothing! Well, almost.

  • Your project must be using Apostrophe 3.x.
  • You'll need to npm update your project to the latest version of apostrophe.
  • You'll need to set the APOS_EXTERNAL_FRONT_KEY environment variable to a secret value of your choosing when running Apostrphe.
  • Make sure you set that same value when running your Astro project.
  • To avoid developer confusion, we recommend changing any page templates in your Apostrophe project to provide a link to your Astro frontend site and remove all other output. Everyone, editors included, should go straight to Astro.

Starting up your combined project

To start your Astro project, follow the usual practice:

cd my-astro-project
npm install
export APOS_EXTERNAL_FRONT_KEY=your-secret-goes-here
npm run dev

In an adjacent terminal, start your Apostrophe project:

cd my-apostrophe-project
npm install
export APOS_EXTERNAL_FRONT_KEY=your-secret-goes-here
npm run dev

For convenience, Astro generally defaults to port 4321, while Apostrophe defaults to port 3000.

Logging in

Once your integration is complete, you will be able to reach the login page in the usual way at http://localhost:4321/login. Astro proxies this route directly to Apostrophe. Therefore any additional extensions you have added such as Apostrophe's hCaptcha and TOTP modules will work as expected.

Redirections

When Apostrophe sends a response as a redirection, you will receive a specially formatted aposData object containing redirect: true, a url property for the url to redirect to, and a status for the redirection HTTP status code. This is handled in the earlier example, repeated here for convenience:

const aposData = await aposPageFetch(Astro.request)
// Redirect
if (aposData.redirect) {
  return Astro.redirect(aposData.url, aposData.status);
}

404 Not Found

Much like the redirect case, when Apostrophe determines that the page was not found, aposData.notFound will be set to true. The example [...slug].astro file provided above includes logic to set Astro's status code to 404 in this situation.

Reserved routes

As this integration proxies certain Apostrophe endpoints, there are some routes that are taken by those endpoints:

  • /apos-frontend/[...slug] for serving Apostrophe assets
  • /uploads/[...slug] for serving Apostrophe uploaded assets
  • /api/v1/[...slug] and /[locale]/api/v1/[...slug] for Apostrophe API endpoints
  • /login and /[locale]/login for the login page

As all Apostrophe API endpoints are proxied, you can expose new api routes as usual in your Apostrophe modules, and be able to request them through your Astro application.
Those proxies are forwarding all of the original request headers, such as cookies, so that Apostrophe login works normally.

What about widget players?

ApostropheCMS is very unopinionated on the front end, but it does include one important front end feature: widget players. These provide a way for developers to provide special behavior to widgets, calling each widget's player exactly once at page load and when new widgets are inserted or replaced with new values. Users appreciate this and expect interactive widget features to work normally without a page refresh, even if the widget was just added to the page.

In Astro, web components are a recommended strategy to achieve the same thing. Defining and using a web component in an Astro widget component has much the same effect as defining a widget player in a standalone Apostrophe project.

Here is a simple outline of such a web component. For a complete example of the same widget, check out the source code of VideoWidget.astro in our apostrophecms/astro-frontend project.

---
// src/widgets/VideoWidget.astro
const { widget } = Astro.props;
const placeholder = widget?.aposPlaceholder ? 'true' : '';
const url = widget?.video?.url;
---
<style>
  video-widget {
    width: 100%;
  }
</style>
<video-widget
  url={placeholder ? 'https://youtu.be/Q5UX9yexEyM' : url }
>
</video-widget>
<script>
  class VideoWidget extends HTMLElement {
    constructor() {
      super();
      this.init();
    }
    async init() {
      const videoUrl = this.getAttribute('url');
      // Your logic here!
      //
      // Fetch details about the video URL,
      // create an iframe to embed it, append it
      // to the component's HTML element with this.append(),
      // etc.
    }
  }
  customElements.define('video-widget', VideoWidget);
</script>

Note that Astro script tags aren't really plain vanilla HTML script tags. They are efficiently compiled, support TypeScript and are only executed once even if the component appears may times on the page. Defining a web component allows us to leverage that code more than once by using the newly defined element as often as we wish.

aposSetQueryParameter: working with query parameters

One last thing: query parameters. Sometimes we want to create pagination links with page numbers, add filters to a URL's query string, and so on. But, working with query parameters coming from Apostrophe can be a little bit tricky because there are often special query parameters present during editing that should not be part of a visible URL.

As a convenience, Apostrophe provides aposSetQueryParameter to abstract all that away.

Here is how the BlogIndexPage.astro component of the apostrophecms/astro-frontend project generates links to the each page of blog posts:

---
import setParameter from '@apostrophecms/apostrophe-astro/lib/aposSetQueryParameter.js';

const {
  pieces,
  currentPage,
  totalPages
} = Astro.props.aposData;

const pages = [];
for (let i = 1; (i <= totalPages); i++) {
  pages.push({
    number: i,
    current: page === currentPage,
    url: setParameter(Astro.url, 'page', i)
  });
}
---

<section class="bp-content">
  <h1>{ page.title }</h1>

  <h2>Blog Posts</h2>

  {pieces.map(piece => (
    <h3>
      <a href={ piece._url }>{ piece.title }</a>
    </h3>
  ))}

  {pages.map(page => (
    <a
      class={(page === currentPage) ? 'current' : ''} 
      href={page.url}>{page.number}
    </a>
  ))}
</section>

Imported here as setParameter, aposSetQueryParameter allows us to do two things:

  1. Take a URL and return a new URL with a certain query parameter set to a new value.
  2. Remove a query parameter completely by passing the empty string as a value, or by passing null or undefined.

While you can get the same result by manipulating Astro.url yourself, you'll be able to avoid the confusing presence of query parameters like aposMode by using this convenient feature.

What about Vue, React, SvelteJS, etc.?

While not shown directly in the examples above, Astro can import components written in any of these frameworks. Just use astro add to install the appropriate integration, then import your components freely in your .astro files. For complete documentation and examples, see the @astrojs/react integration.

In this way, Astro acts as a universal bridge to essentially all modern frontend frameworks.

A note on production use

For production use, any Astro hosting adapter that supports mode: 'server' should be acceptable. In particular, our apostrophecms/astro-frontend project comes pre-configured for the node adapter, and includes npm run build and npm run serve support to take advantage of that. In server mode there is not a great deal of difference between these and npm run dev, but there is less overhead and less information exposed to the public, so we recommend following this best practice.

Debugging

In most cases, Astro prints helpful error messages directly in the browser when in a development environment.

However, if you receive the following error:

Only URLs with a scheme in: file and data are supported by the default ESM
loader. Received protocol 'virtual:'

Then you most likely left out this part of the above Astro.config.js file:

export default defineConfig({
  // ... other settings above here ...
  vite: {
    ssr: {
      // Do not externalize the @apostrophecms/apostrophe-astro plugin, we need
      // to be able to use virtual: URLs there
      noExternal: [ '@apostrophecms/apostrophe-astro' ],
    }
  }
});

Without this logic, the virtual: URLs used to access configuration information will cause the build to fail.

Conclusion

This module provides a new way to use ApostropheCMS: as a back end for modern front end development in Astro. But more than that, it provides a future-proof bridge to many different front-end frameworks.

Also important, Apostrophe fully maintains the on-page, in-context editing experience when integrated with Astro, going beyond "side-by-side" editing experiences to achieve integration close enough that we often have to look at the address bar to know whether we are looking at Astro or Apostrophe.

That being said, this integration is also new, and we encourage you to share your feedback.

Acknowledgements

Development of this module began with Stéphane Maccari and Clément Ravier of Michelin. We are grateful for their generous support of ApostropheCMS.