chore(docs): Adapters

docs/docs/how-to/previews-deploys-hosting/adapters.md

@@ -0,0 +1,58 @@
+---
+title: Adapters
+---
+
+## Introduction
+
+Adapters are responsible for taking the production output from Gatsby and turning it into something your deployment platform understands. They make it easier to build and deploy Gatsby sites on any deployment platform.
+
+Gatsby has different [rendering options](/docs/conceptual/rendering-options/) and features like Deferred Static Generation (DSG) and Server-Side rendering (SSR) require more setup than classic static site generation (SSG). Users can also set [HTTP headers](/docs/how-to/previews-deploys-hosting/headers/) or create [redirects](/docs/reference/config-files/actions/#createRedirect).
+
+Gatsby passes all the required information during the build to adapters to prepare these outputs for deployment on a specific platform. Here are some of the actions an adapter automatically takes:
+
+- Applies HTTP headers to assets
+- Applies redirects and rewrites. The adapter can also create its own redirects or rewrites if necessary, for example to map serverless functions to internal URLs.
+- Wraps serverless functions coming from Gatsby with platform-specific code (if necessary). Gatsby will produce [Express](https://expressjs.com/)-like handlers.
+- Apply trailing slash behavior and path prefix to URLs
+- Possibly uploads assets to CDN
+
+This feature was added in `gatsby@5.X.0`.
+
+## Finding adapters
+
+You can use these official adapters:
+
+- [gatsby-adapter-netlify](https://github.com/gatsbyjs/gatsby/tree/master/packages/gatsby-adapter-netlify) for [Netlify](https://www.netlify.com/)
+
+To find additional community adapters, [search npm for `gatsby-adapter`](https://www.npmjs.com/search?q=gatsby-adapter-).
+
+Can't find an adapter for your platform? Consider [creating an adapter](/docs/how-to/previews-deploys-hosting/creating-an-adapter/) yourself.
+
+## Using adapters
+
+Use the `adapter` option inside `gatsby-config`:
+
+```js:title=gatsby-config.js
+const adapter = require("gatsby-adapter-foo")
+
+module.exports = {
+  adapter: adapter()
+}
+```
+
+If the adapter accepts custom options, you can set them like this:
+
+```js:title=gatsby-config.js
+const adapter = require("gatsby-adapter-foo")
+
+module.exports = {
+  adapter: adapter({
+    // Adapter options
+  })
+}
+```
+
+## Additional resources
+
+- [Zero-Configuration Deployments](/docs/how-to/previews-deploys-hosting/zero-configuration-deployments/)
+- [Creating an Adapter](/docs/how-to/previews-deploys-hosting/creating-an-adapter/)

docs/docs/how-to/previews-deploys-hosting/caching.md

@@ -4,7 +4,7 @@ title: Caching Static Sites
 
 An important part of creating a very fast website is setting up proper HTTP caching. HTTP caching allows browsers to cache resources from a website so that when the user returns to a site, very few parts of the website have to be downloaded.
 
-Different types of resources are cached differently. Let's examine how the different types of files built to `public/` should be cached.
+Different types of resources are cached differently. Let's examine how the different types of files built to `public` should be cached.
 
 ## HTML
 
@@ -38,7 +38,7 @@ cache-control: public, max-age=0, must-revalidate
 
 ## Static files
 
-All files in `static/` should be cached forever. For files in this directory, Gatsby creates paths that are directly tied to the content of the file. Meaning that if the file content changes, then the file path changes also. These paths look weird e.g. `some-name-e097c4319d0f8cff6-0b1ba.png` but since the same file will always be returned when that path is requested, Gatsby can cache it forever.
+All files in `static` should be cached forever. For files in this directory, Gatsby creates paths that are directly tied to the content of the file. Meaning that if the file content changes, then the file path changes also. These paths look weird e.g. `some-name-e097c4319d0f8cff6-0b1ba.png` but since the same file will always be returned when that path is requested, Gatsby can cache it forever.
 
 The `cache-control` header should be:
 
@@ -48,7 +48,7 @@ cache-control: public, max-age=31536000, immutable
 
 ## JavaScript and CSS
 
-JavaScript and CSS files _generated by webpack_ should also be cached forever. Like static files, Gatsby creates JS & CSS file names (as a hash!) based on the file content. If the file content is changed, the file hash will change, therefore these files _generated by webpack_ are safe to cache.
+JavaScript and CSS files _generated by webpack_ should also be cached forever. Like static files, Gatsby creates JS & CSS file names (as a hash) based on the file content. If the file content is changed, the file hash will change, therefore these files _generated by webpack_ are safe to cache.
 
 The `cache-control` header should be:
 
@@ -62,13 +62,14 @@ The only exception to this is the file `/sw.js`, which needs to be revalidated u
 cache-control: public, max-age=0, must-revalidate
 ```
 
-## Setting up caching on different hosts
+## Setting up caching on different deployment platforms
 
-How you set up your caching depends on how you host your site. We encourage people to create Gatsby plugins per host to automate the creation of caching headers.
+How you set up your caching depends on how you host your site. We encourage you to use a [Gatsby adapter](/docs/how-to/previews-deploys-hosting/adapters/) for your deployment platform (if available) to automate the creation and application of the caching headers mentioned above.
 
-The following plugins have this functionality:
+If an adapter doesn’t exist for your deployment platform yet, consider [creating an adapter](/docs/how-to/previews-deploys-hosting/creating-an-adapter/).
+
+Since Gatsby adapters were introduced in later Gatsby releases, you could also look out for plugins like:
 
-- [gatsby-plugin-netlify](/plugins/gatsby-plugin-netlify/)
 - [gatsby-plugin-s3](/plugins/gatsby-plugin-s3/)
 - [gatsby-plugin-fastify](/plugins/gatsby-plugin-fastify/)
 

docs/docs/how-to/previews-deploys-hosting/creating-an-adapter.md

@@ -0,0 +1,292 @@
+---
+title: Creating an Adapter
+examples:
+  - label: gatsby-adapter-netlify
+    href: "https://github.com/gatsbyjs/gatsby/tree/master/packages/gatsby-adapter-netlify"
+---
+
+import Collapsible from "@components/collapsible"
+
+## Introduction
+
+If an [adapter](/docs/how-to/previews-deploys-hosting/adapters/) for your preferred deployment platform doesn't exist yet, you can build your own. While the specifics of the adapter depend on the deployment platform and its requirements, the initial setup is the same for every adapter.
+
+By the end of this guide you should be able to create and publish an adapter.
+
+The adapters feature was added in `gatsby@5.X.0`.
+
+## Authoring
+
+An adapter's entry point should have the following API:
+
+```js
+/**
+ * @type {import("gatsby").AdapterInit}
+ */
+const createAdapterFoo = adapterOptions => {
+  return {
+    name: `gatsby-adapter-foo`,
+    cache: {
+      restore({ directories, reporter }) {
+        // Cache restore implementation
+      },
+      store({ directories, reporter }) {
+        // Cache store implementation
+      },
+    },
+    adapt({
+      routesManifest,
+      functionsManifest,
+      pathPrefix,
+      trailingSlash,
+      reporter,
+    }) {
+      // Adapt implementation
+    },
+    config({ reporter }) {
+      // Information passed back to Gatsby
+    },
+  }
+}
+
+module.exports = createAdapterFoo
+```
+
+<Collapsible
+  summary={<em>TypeScript version</em>}
+>
+
+Gatsby makes a `AdapterInit` type available that you can use to author your adapter. It also accepts a generic for the adapter options:
+
+```ts
+import type { AdapterInit } from "gatsby"
+
+type AdapterOptions = {
+  foo: boolean
+}
+
+const createAdapterFoo: AdapterInit<AdapterOptions> = ({ foo }) => {
+  return {
+    name: `gatsby-adapter-foo`,
+    cache: {
+      restore({ directories, reporter }) {
+        // Cache restore implementation
+      },
+      store({ directories, reporter }) {
+        // Cache store implementation
+      },
+    },
+    adapt({
+      routesManifest,
+      functionsManifest,
+      pathPrefix,
+      trailingSlash,
+      reporter,
+    }) {
+      // Adapt implementation
+    },
+    config({ reporter }) {
+      // Information passed back to Gatsby
+    },
+  }
+}
+
+export default createAdapterFoo
+```
+
+You can find all TypeScript types [on GitHub](https://github.com/gatsbyjs/gatsby/blob/master/packages/gatsby/src/utils/adapter/types.ts).
+
+</Collapsible>
+
+The adapter should export a function as a default export with these object keys:
+
+- `name`: Unique name of the adapter. Please follow the naming convention `gatsby-adapter-<name>` or `@scope/gatsby-adapter-<name>` to make it easier for people to discover your adapter.
+- `cache` (Optional): Both handlers receive `directories` which are the directories that should be cached/restored for a build and the [`reporter` instance](/docs/reference/config-files/node-api-helpers/#reporter).
+  - `restore`: Hook to restore `directories` from previous builds. Executed very early on in the build process. If the hook returns `false`, Gatsby will skip cache restoration.
+  - `store`: Hook to store `directories` for the current build. Executed as one of the last steps in the build process.
+- [`adapt`](#adapt): Hook to take Gatsby's output and prepare it for deployment on the adapter's platform. Executed as one of the last steps in the build process. Details on the inputs are [documented below](#adapt).
+- `config` (Optional): Hook to pass information from the adapter to Gatsby so it can adjust its build process. This hook can enable advanced features of adapters to e.g. workaround platform limitations. The adapter has to return an object with the following keys:
+  - `deployURL` (Optional): URL representing the unique URL for an individual deploy
+  - `excludeDatastoreFromEngineFunction` (Optional): If `true`, Gatsby will not include the LMDB datastore in the serverless functions used for SSR/DSG. Instead, it will place the LMDB datastore into the `public` folder and later try to download the datastore from the given `deployURL`.
+
+If your adapter accepts custom options, consider setting default values to make the adapter easier to use.
+
+`cache.restore`, `cache.store`, and `adapt` receive the [`reporter` instance](/docs/reference/config-files/node-api-helpers/#reporter), so you can output structured logs to the user’s terminal. **However**, please don’t overdo it and keep the output to a minimum. If a user requires more details, they can always use the CLI with the `--verbose` flag to get information about the adapter and logs for debugging.
+
+### adapt
+
+The `adapt` hook takes Gatsby's output and prepares it for deployment on the adapter's platform. It receives the following inputs:
+
+- `routesManifest`: Array of objects with three different types: `static`, `function`, and `redirect`. Each object contains all necessary information to deploy and apply these routes. `static` routes will have default `headers` applied, which users can extend or overwrite with the [HTTP headers](/docs/how-to/previews-deploys-hosting/headers/) option inside `gatsby-config`. Routes will also have the [`trailingSlash`](/docs/reference/config-files/gatsby-config/#trailingslash) option applied to their paths.
+- `functionsManifest`: Array of objects containing each function's entry point and required files.
+- `pathPrefix`: Value of the [`pathPrefix`](/docs/reference/config-files/gatsby-config/#pathprefix) option inside `gatsby-config`
+- `trailingSlash`: Value of the [`trailingSlash`](/docs/reference/config-files/gatsby-config/#trailingslash) option inside `gatsby-config`
+
+You can find the TypeScript types for these inputs on [on GitHub](https://github.com/gatsbyjs/gatsby/blob/master/packages/gatsby/src/utils/adapter/types.ts).
+
+The `adapt` hook should do the following things:
+
+- Apply HTTP headers to assets
+- Apply redirects and rewrites. The adapter can also create its own redirects and rewrites, if necessary (e.g. mapping serverless functions to internal URLs).
+- Wrap serverless functions coming from Gatsby with platform-specific code (if necessary). Gatsby will produce [Express](https://expressjs.com/)-like handlers.
+- Apply trailing slash behavior and path prefix to URLs
+- Possibly upload assets to CDN
+
+## Testing locally
+
+If you want to test your adapter locally, you can use [npm link](https://docs.npmjs.com/cli/v9/commands/npm-link), [yarn link](https://yarnpkg.com/cli/link), or equivalent in other package managers. You'd use your adapter like so:
+
+```js:title=gatsby-config.js
+// gatsby-adapter-foo would be your linked adapter
+const adapter = require("gatsby-adapter-foo")
+
+module.exports = {
+  adapter: adapter()
+}
+```
+
+If you want to quickly prototype an adapter, you can also author your file(s) directly in an example project (before moving them to their own repository). Here's how:
+
+1. Create an adapter file called `gatsby-adapter-foo.js` at the root of your project:
+
+   ```js:title=gatsby-adapter-foo.js
+   const createAdapterFoo = adapterOptions => {
+     return {
+       name: `gatsby-adapter-foo`,
+       // cache hooks...
+       adapt({
+        routesManifest,
+        functionsManifest,
+        pathPrefix,
+        trailingSlash,
+        reporter
+       }) {
+         // Adapt implementation
+         reporter.info('gatsby-adapter-foo is working')
+       },
+     }
+   }
+
+   module.exports = createAdapterFoo
+   ```
+
+1. Import the adapter file into your `gatsby-config`:
+
+   ```js:title=gatsby-config.js
+   const adapter = require("./gatsby-adapter-foo")
+
+   module.exports = {
+     adapter: adapter()
+   }
+   ```
+
+1. Once it works, don't forget to [publish](#publishing) your adapter so that the community can benefit from it.
+
+## Publishing
+
+You'll need to publish your adapter to [npm](https://www.npmjs.com/) so that others can use it. If this is your first time publishing to npm, consider following their [guides](https://docs.npmjs.com/packages-and-modules/contributing-packages-to-the-registry).
+
+Before you publish, keep in mind that once people start using your adapter, you'll need to make changes responsibly (following [semver](https://docs.npmjs.com/about-semantic-versioning)) and potentially automate some of the maintenance work.
+
+We recommend that you follow this checklist before you publish your adapter for the first time:
+
+- Choose a clear name for your adapter following this naming convention:
+
+  ```
+  gatsby-adapter-<name>
+  ```
+
+  To publish the adapter under a [scope](https://docs.npmjs.com/about-scopes), follow this naming convention:
+
+  ```
+  @scope/gatsby-adapter-<name>
+  ```
+
+- Your `README` should explain to the user in concise steps how to install, use, and configure your adapter (also see [How to write a plugin README](/contributing/docs-contributions/how-to-write-a-plugin-readme/)). The `README` will be the first thing a user reviews so make sure that it's accessible to everyone.
+- Set `1.0.0` as the `version` field in your adapter's `package.json`. For future releases, follow [semantic versioning](https://docs.npmjs.com/about-semantic-versioning).
+
+  ```json:title=package.json
+  {
+    "version": "1.0.0",
+  }
+  ```
+
+- Include a `keywords` field in your adapter's `package.json`, containing `gatsby`, `gatsby-plugin`, and `gatsby-adapter`. This way the adapter can be found through the [plugin library](/plugins/).
+
+  ```json:title=package.json
+  {
+    "keywords": [
+      "gatsby",
+      "gatsby-plugin",
+      "gatsby-adapter"
+    ],
+  }
+  ```
+
+- Include a `peerDependencies` field in your adapter's `package.json`, containing the `gatsby` version range that your adapter is compatible with.
+
+  For example, if your adapter supports Gatsby 5 only (e.g. it uses an API only available in Gatsby 5), use:
+
+  ```json:title=package.json
+  {
+    "peerDependencies": {
+      "gatsby": "^5.0.0"
+    }
+  }
+  ```
+
+  If Gatsby releases a new major version and your adapter doesn't require the new changes, you can mark your adapter as compatible with specific versions. For example, to mark your adapter as compatible with Gatsby 5 and Gatsby 6:
+
+  ```json:title=package.json
+  {
+    "peerDependencies": {
+      "gatsby": "^5.0.0 || ^6.0.0"
+    }
+  }
+  ```
+
+- Add a `build` script to your adapter's `package.json`. The `build` script should compile your source code to **CommonJS (CJS)** into a `dist` folder. If you're authoring the code in TypeScript, also consider generating type definitions. If you're authoring the code in CJS already there is no need for a `build` script.
+
+  Depending on your tooling (e.g. [microbundle](https://github.com/developit/microbundle), [Babel](https://babeljs.io/), [Parcel](https://parceljs.org/), [tsup](https://github.com/egoist/tsup)) adjust your build script:
+
+  ```json:title=package.json
+  {
+    "scripts": {
+      "build": "your-build-script",
+    }
+  }
+  ```
+
+  Since your compiled information will be in the `dist` folder, you need to also add a `main` and `files` key to the `package.json`.
+
+  ```json:title=package.json
+  {
+    "main": "./dist/index.js",
+    "files": [
+      "./dist/*"
+    ],
+  }
+  ```
+
+  If you've generated TypeScript types, consider [adding a `types` key](https://www.typescriptlang.org/docs/handbook/declaration-files/publishing.html).
+
+- Add a `prepare` script to your adapter's `package.json` that runs before `npm publish`. If the `build` script doesn't automatically clear the `dist` folder before a new build, add an additional `clean` script. This ensures that old artifacts aren't accidentally published. For example, if you rename a file and don't run `clean`, the old file will still be published through `dist`. You could use [del-cli](https://www.npmjs.com/package/del-cli) to achieve this. It would look something like this:
+
+  ```json:title=package.json
+  {
+    "scripts": {
+      "clean": "del-cli dist",
+      "build": "your-build-script",
+      "prepare": "npm run clean && npm run build"
+    }
+  }
+  ```
+
+- Follow the other recommendations from npm's [Creating a package.json file](https://docs.npmjs.com/creating-a-package-json-file) documentation, e.g. adding a `description` or `author` field.
+
+## Additional resources
+
+- [gatsby-adapter-netlify source code](https://github.com/gatsbyjs/gatsby/tree/master/packages/gatsby-adapter-netlify)
+- [Adapters](/docs/how-to/previews-deploys-hosting/adapters/)
+- [Zero-Configuration Deployments](/docs/how-to/previews-deploys-hosting/zero-configuration-deployments/)
+- [Gatsby Adapters RFC](https://github.com/gatsbyjs/gatsby/discussions/38231)