feat(netlify): Netlify Adapter v4

.changeset/ten-cougars-pretend.md

@@ -0,0 +1,69 @@
+---
+'@astrojs/netlify': major
+---
+
+# Netlify Adapter v4 simplifies static + SSR deployments
+
+This update is a complete overhaul of the Netlify adapter.
+It simplifies the user-facing config, and resolves a number of bugs along the way.
+
+Here's what changes:
+
+## Netlify Context is automatically available via Locals
+
+In v3, you could use `netlify-edge-middleware.ts` to inject data from the Netlify context into your Astro locals.
+In v4, this file is no longer needed because the Netlify context is automatically made available via `Astro.locals.netlify.context`.
+You can use this context to access information about the user (like geolocation or IP address), your Netlify site (like deploy ID) or the request (like its request ID or the CDN region it's served from).
+
+**Action Required:**
+Remove the `netlify-edge-middleware.ts` or `netlify-edge-middleware.js` file.
+In your codebase, change all usage of locals injected through that file to use `Astro.locals.netlify.context` instead.
+
+### Image CDN
+
+v4 of this adapter integrates your Astro site with Netlify [Image CDN](https://docs.netlify.com/image-cdn/overview/).
+This allows transforming images on-the-fly without impacting build times.
+It's implemented using an [Astro Image Service](https://docs.astro.build/en/reference/image-service-reference/), and enabled by default.
+
+## On-Demand Builders are no longer supported
+
+On-Demand Builders (ODB) allows SSR-Rendered pages to be cached using a Time to Live (TTL) strategy.
+ODB continues to be supported by Netlify, but has since been replaced by the much more powerful
+[Fine-Grained Cache Control](https://www.netlify.com/blog/swr-and-fine-grained-cache-control).
+
+In v3, you could deploy your SSR-Rendered Astro pages to ODBs by enabling the `builders` config option,
+and then specifying the TTL on a per-page basis.
+In v4, there's the `cacheOnDemandPages` option that works very similarly - take a look at the README to learn more.
+
+**Action Required:**
+Replace the `builders` config option with `cacheOnDemandPages`.
+
+```diff lang="ts"
+// astro.config.mjs
+export default defineConfig({
+  // ...
+  adapter: netlify({
+-   builders: true
++   cacheOnDemandPages: true
+  }),
+});
+```
+
+## `functionPerRoute` was removed
+
+In v3, the `functionPerRoute` option allowed the SSR routes to be split up into multiple Netlify Functions.
+In theory, this reduced bundle sizes of each individual function, and the speed-up in code parsing should speed up cold starts.
+In practice, this benefit is often nullified by the increase in number of cold starts - more handlers means fewer requests per handler, means more cold starts.
+
+In v4, support for this deployment mode was removed.
+
+**Action Required:**
+Remove the `functionPerRoute` field from your config.
+
+## `binaryMediaTypes` was removed
+
+`binaryMediaTypes` was a workaround required for some Astro endpoints, because v3 deployed those as "old" Netlify Functions (now referred to as ["Lambda Compatibility Mode"](https://docs.netlify.com/functions/lambda-compatibility)).
+v4 uses the new [Netlify Functions 2.0](https://www.netlify.com/blog/introducing-netlify-functions-2-0/), which simply doesn't need this workaround anymore - so we're removing it 🎉
+
+**Action Required:**
+Remove the `binaryMediaTypes` field from your config.

packages/netlify/README.md

@@ -1,13 +1,12 @@
 # @astrojs/netlify
 
-This adapter allows Astro to deploy your SSR site to [Netlify](https://www.netlify.com/).
+This adapter allows Astro to deploy your On-Demand-Rendered site to [Netlify](https://www.netlify.com/).
 
 Learn how to deploy your Astro site in our [Netlify deployment guide](https://docs.astro.build/en/guides/deploy/netlify/).
 
 - <strong>[Why Astro Netlify](#why-astro-netlify)</strong>
 - <strong>[Installation](#installation)</strong>
 - <strong>[Usage](#usage)</strong>
-- <strong>[Configuration](#configuration)</strong>
 - <strong>[Examples](#examples)</strong>
 - <strong>[Troubleshooting](#troubleshooting)</strong>
 - <strong>[Contributing](#contributing)</strong>
@@ -17,13 +16,13 @@ Learn how to deploy your Astro site in our [Netlify deployment guide](https://do
 
 If you're using Astro as a static site builder—its behavior out of the box—you don't need an adapter.
 
-If you wish to [use server-side rendering (SSR)](https://docs.astro.build/en/guides/server-side-rendering/), Astro requires an adapter that matches your deployment runtime.
+If you wish to [use On-Demand Rendering, also known as Server-Side Rendering (SSR)](https://docs.astro.build/en/guides/server-side-rendering/), Astro requires an adapter that matches your deployment runtime.
 
 [Netlify](https://www.netlify.com/) is a deployment platform that allows you to host your site by connecting directly to your GitHub repository. This adapter enhances the Astro build process to prepare your project for deployment through Netlify.
 
 ## Installation
 
-Add the Netlify adapter to enable SSR in your Astro project with the following `astro add` command. This will install the adapter and make the appropriate changes to your `astro.config.mjs` file in one step.
+Add the Netlify adapter to enable On-Demand Rendering in your Astro project with the following `astro add` command. This will install the adapter and make the appropriate changes to your `astro.config.mjs` file in one step.
 
 ```sh
 # Using NPM
@@ -49,81 +48,91 @@ If you prefer to install the adapter manually instead, complete the following tw
    ```diff lang="js"
      // astro.config.mjs
      import { defineConfig } from 'astro/config';
-   + import netlify from '@astrojs/netlify/functions';
+   + import netlify from '@astrojs/netlify';
 
      export default defineConfig({
    +   output: 'server',
    +   adapter: netlify(),
      });
    ```
 
-### Run middleware in Edge Functions
+## Usage
 
-When deploying to Netlify Functions, you can choose to use an Edge Function to run your Astro middleware.
+[Read the full deployment guide here.](https://docs.astro.build/en/guides/deploy/netlify/)
 
-To enable this, set the `edgeMiddleware` config option to `true`:
+After [performing a build](https://docs.astro.build/en/guides/deploy/#building-your-site-locally) the `.netlify/` folder will contain [Netlify Functions](https://docs.netlify.com/functions/overview/) in the `.netlify/functions-internal/` and [Netlify Edge Functions](https://docs.netlify.com/edge-functions/overview/) in the `.netlify/edge-functions/` folder.
 
-```diff lang="js"
-  // astro.config.mjs
-  import { defineConfig } from 'astro/config';
-  import netlify from '@astrojs/netlify/functions';
-
-  export default defineConfig({
-    output: 'server',
-    adapter: netlify({
-+     edgeMiddleware: true,
-    }),
-  });
+Now you can deploy. Install the [Netlify CLI](https://docs.netlify.com/cli/get-started/) and run:
+
+```sh
+netlify deploy
 ```
 
-#### Pass edge context to your site
+The [Netlify Blog post on Astro](https://www.netlify.com/blog/how-to-deploy-astro/) and the [Netlify Docs](https://docs.netlify.com/integrations/frameworks/astro/) provide more information on how to use this integration to deploy to Netlify.
 
-Netlify Edge Functions provide a [context object](https://docs.netlify.com/edge-functions/api/#netlify-specific-context-object) including metadata about the request, such as a user’s IP, geolocation data, and cookies.
 
-To expose values from this context to your site, create a `netlify-edge-middleware.ts` (or `.js`) file in your project’s [source directory](https://docs.astro.build/en/reference/configuration-reference/#srcdir). This file must export a function that returns the data to add to [Astro’s `locals` object](https://docs.astro.build/en/reference/api-reference/#astrolocals), which is available in middleware and Astro routes.
+### Accessing edge context from your site
 
-In this example, `visitorCountry` and `hasEdgeMiddleware` would both be added to Astro’s `locals` object:
+Netlify Edge Functions provide a [context object](https://docs.netlify.com/edge-functions/api/#netlify-specific-context-object) that includes metadata about the request such as a user’s IP, geolocation data, and cookies.
 
-```ts
-// src/netlify-edge-middleware.ts
-import type { Context } from 'https://edge.netlify.com';
-
-export default function ({ request, context }: { request: Request; context: Context }) {
-  // Return serializable data to add to Astro.locals
-  return {
-    visitorCountry: context.geo.country.name,
-    hasEdgeMiddleware: true,
-  };
-}
+This can be accessed through the `Astro.locals.netlify.context` object:
+
+```astro
+---
+const { geo: { city } } = Astro.locals.netlify.context
+---
+<h1>Hello there, friendly visitor from {city}!</h1>
 ```
 
-> **Note**
-> Netlify Edge Functions run in [a Deno environment](https://docs.netlify.com/edge-functions/api/#runtime-environment), so import statements in this file must use Deno’s URL syntax.
+If you're using TypeScript, you can get proper typings by updating your `src/env.d.ts` to use `NetlifyLocals`:
 
-`netlify-edge-middleware.ts` must provide a function as its default export. This function:
+```ts
+// src/env.d.ts
+/// <reference path="../.astro/types.d.ts" />
+/// <reference types="astro/client" />
 
-- must return a JSON-serializable object, which cannot include types like `Map`, `function`, `Set`, etc.
-- will always run first, before any other middleware and routes.
-- cannot return a response or redirect.
+type NetlifyLocals = import('@astrojs/netlify').NetlifyLocals
 
-### Per-page functions
+declare namespace App {
+  interface Locals extends NetlifyLocals {
+    ...
+  }
+}
+```
 
-The Netlify adapter builds to a single function by default. Astro 2.7 added support for splitting your build into separate entry points per page. If you use this configuration, the Netlify adapter will generate a separate function for each page. This can help reduce the size of each function so they are only bundling code used on that page.
+It's only available during on-demand rendering.
 
-```js
+### Run Middleware in Edge Functions
+
+If you use Astro Middleware, the default behaviour is that it's applied to prerendered pages at build-time, and to on-demand-rendered pages at runtime.
+For prerendered pages, it can't be used to implement redirects, access control or custom response headers.
+If you need any of this, you should probably deploy run your Middleware on Netlify Edge Functions by enabling the `edgeMiddleware` option:
+
+```diff lang="js"
 // astro.config.mjs
 import { defineConfig } from 'astro/config';
 import netlify from '@astrojs/netlify/functions';
 
 export default defineConfig({
   output: 'server',
   adapter: netlify({
-    functionPerRoute: true,
++   edgeMiddleware: true,
   }),
 });
 ```
 
-### Static sites
+This will deploy your Middleware as an Edge Function, and run it on all routes - including prerendered pages.
+This also means that locals specified in the Middleware won't be applied to any prerendered pages, because they've already been fully rendered at build-time.
+
+### Image CDN
+
+This adapter integrates your site with [Netlify Image CDN](https://docs.netlify.com/image-cdn/), transforming images on-the-fly without impacting build times.
+It's implemented using an [Astro Image Service](https://docs.astro.build/en/reference/image-service-reference/) under the hood.
+
+> **Note**
+> This adapter does not support `image.domains` and `image.remotePatterns` config properties in your Astro config - use the `remote_images` field in `netlify.toml` instead: [Netlify Image CDN - Remote Path](https://docs.netlify.com/image-cdn/overview/#remote-path).
+
+### Static sites & Redirects
 
 For static sites you usually don't need an adapter. However, if you use `redirects` configuration in your Astro config, the Netlify adapter can be used to translate this to the proper `_redirects` format.
 
@@ -146,117 +155,40 @@ Once you run `astro build` there will be a `dist/_redirects` file. Netlify will
 > **Note**
 > You can still include a `public/_redirects` file for manual redirects. Any redirects you specify in the redirects config are appended to the end of your own.
 
-### On-demand Builders
-
-[Netlify On-demand Builders](https://docs.netlify.com/configure-builds/on-demand-builders/) are serverless functions used to generate web content as needed that’s automatically cached on Netlify’s Edge CDN. You can enable these functions using the [`builders` configuration](#builders).
-
-By default, all pages will be rendered on first visit and the rendered result will be reused for every subsequent visit until you redeploy. To set a revalidation time, call the [`runtime.setBuildersTtl(ttl)` local](https://docs.astro.build/en/reference/api-reference/#astrolocals) with the duration (in seconds).
-
-The following example sets a revalidation time of 45, causing Netlify to store the rendered HTML for 45 seconds.
-
-```astro
----
-// src/pages/index.astro
-import Layout from '../components/Layout.astro';
-
-if (import.meta.env.PROD) {
-  Astro.locals.runtime.setBuildersTtl(45);
-}
----
-
-<Layout title="Astro on Netlify">
-  {new Date(Date.now())}
-</Layout>
-```
-
-It is important to note that On-demand Builders ignore query params when checking for cached pages. For example, if `example.com/?x=y` is cached, it will be served for `example.com/?a=b` (different query params) and `example.com/` (no query params) as well.
-
-## Usage
-
-[Read the full deployment guide here.](https://docs.astro.build/en/guides/deploy/netlify/)
-
-After [performing a build](https://docs.astro.build/en/guides/deploy/#building-your-site-locally) the `netlify/` folder will contain [Netlify Functions](https://docs.netlify.com/functions/overview/) in the `netlify/functions/` folder.
-
-Now you can deploy. Install the [Netlify CLI](https://docs.netlify.com/cli/get-started/) and run:
-
-```sh
-netlify deploy --build
-```
-
-The [Netlify Blog post on Astro](https://www.netlify.com/blog/how-to-deploy-astro/) and the [Netlify Documentation](https://docs.netlify.com/integrations/frameworks/astro/) provide more information on how to use this integration to deploy to Netlify.
-
-## Configuration
-
-To configure this adapter, pass an object to the `netlify()` function call in `astro.config.mjs` - there's only one possible configuration option:
+### Caching On-Demand-Rendered Pages
 
-### dist
+On-demand-rendered pages that don't contain dynamic content can be cached to improve performance and lower resource usage.
+The easiest way to do this is to enable the `cacheOnDemandPages` option in the adapter, which will cache all on-demand-rendered pages for up to one year:
 
-We build to the `dist` directory at the base of your project. To change this, use the `dist` option:
-
-```js
+```ts
 // astro.config.mjs
-import { defineConfig } from 'astro/config';
-import netlify from '@astrojs/netlify/functions';
-
 export default defineConfig({
   output: 'server',
   adapter: netlify({
-    dist: new URL('./dist/', import.meta.url),
+    cacheOnDemandPages: true
   }),
 });
 ```
 
-And then point to the dist in your `netlify.toml`:
+For advanced usage, you can change this on a per-page basis by adding caching headers to your response from within your pages:
 
-```toml
-# netlify.toml
-[functions]
-directory = "dist/functions"
-```
-
-### builders
 
-You can enable On-demand Builders using the `builders` option:
+```astro
+---
+// src/pages/index.astro
+import Layout from '../components/Layout.astro';
 
-```js
-// astro.config.mjs
-import { defineConfig } from 'astro/config';
-import netlify from '@astrojs/netlify/functions';
+Astro.response.headers.set('CDN-Cache-Control', "public, max-age=45, must-revalidate")
+---
 
-export default defineConfig({
-  output: 'server',
-  adapter: netlify({
-    builders: true,
-  }),
-});
+<Layout title="Astro on Netlify">
+  {new Date()}
+</Layout>
 ```
 
-On-demand Builders are only available with the `@astrojs/netlify/functions` adapter and are not compatible with Edge Functions.
-
-### binaryMediaTypes
-
-> This option is only needed for the Functions adapter and is not needed for Edge Functions.
-
-Netlify Functions requires binary data in the `body` to be base64 encoded. The `@astrojs/netlify/functions` adapter handles this automatically based on the `Content-Type` header.
-
-We check for common mime types for audio, image, and video files. To include specific mime types that should be treated as binary data, include the `binaryMediaTypes` option with a list of binary mime types.
-
-```js
-// src/pages/image.jpg.ts
-import fs from 'node:fs';
-
-export function GET() {
-  const buffer = fs.readFileSync('../image.jpg');
-
-  // Return the buffer directly, @astrojs/netlify will base64 encode the body
-  return new Response(buffer, {
-    status: 200,
-    headers: {
-      'content-type': 'image/jpeg',
-    },
-  });
-}
-```
+With [fine-grained cache control](https://www.netlify.com/blog/swr-and-fine-grained-cache-control/), Netlify supports
+standard caching headers like `CDN-Cache-Control` or `Vary`.
+Refer to the docs to learn about implementing e.g. time to live (TTL) or stale while revalidate (SWR) caching: https://docs.netlify.com/platform/caching
 
 ## Examples