From 85a3998a08723f13ecdb875e9a6dc271847859b3 Mon Sep 17 00:00:00 2001
From: Chris Kerr <chriskerr@me.com>
Date: Thu, 15 Dec 2022 08:40:35 +1000
Subject: [PATCH] Allow preserving express request keys within adapter node

---
 .changeset/fast-nails-attack.md      |  5 +++++
 packages/adapter-node/README.md      | 13 ++++++++++++-
 packages/adapter-node/index.d.ts     |  1 +
 packages/adapter-node/index.js       |  5 +++--
 packages/adapter-node/src/handler.js |  7 +++++++
 5 files changed, 28 insertions(+), 3 deletions(-)
 create mode 100644 .changeset/fast-nails-attack.md

diff --git a/.changeset/fast-nails-attack.md b/.changeset/fast-nails-attack.md
new file mode 100644
index 0000000000000..b98bb56dc5ef2
--- /dev/null
+++ b/.changeset/fast-nails-attack.md
@@ -0,0 +1,5 @@
+---
+'@sveltejs/adapter-node': minor
+---
+
+Allow preserving specific keys from the original request object for use during SSR
diff --git a/packages/adapter-node/README.md b/packages/adapter-node/README.md
index b6ec4bc1bf623..fa9349b0e048a 100644
--- a/packages/adapter-node/README.md
+++ b/packages/adapter-node/README.md
@@ -116,7 +116,8 @@ export default {
       // default options are shown
       out: 'build',
       precompress: false,
-      envPrefix: ''
+      envPrefix: '',
+      preservedRequestKeys: [],
     })
   }
 };
@@ -145,6 +146,16 @@ MY_CUSTOM_ORIGIN=https://my.site \
 node build
 ```
 
+### preservedRequestKeys
+
+Allows preserving specific keys (such as custom keys set by Express middleware) from the original request object which was supplied to SvelteKit.
+
+This is will allow access to these keys within server hooks and handlers.
+
+```js
+preservedRequestKeys: ['sessionID'],
+```
+
 ## Custom server
 
 The adapter creates two files in your build directory — `index.js` and `handler.js`. Running `index.js` — e.g. `node build`, if you use the default build directory — will start a server on the configured port.
diff --git a/packages/adapter-node/index.d.ts b/packages/adapter-node/index.d.ts
index 2252dfde937cc..fafea4791bb5b 100644
--- a/packages/adapter-node/index.d.ts
+++ b/packages/adapter-node/index.d.ts
@@ -8,6 +8,7 @@ interface AdapterOptions {
 	out?: string;
 	precompress?: boolean;
 	envPrefix?: string;
+	preservedRequestKeys?: string[];
 }
 
 export default function plugin(options?: AdapterOptions): Adapter;
diff --git a/packages/adapter-node/index.js b/packages/adapter-node/index.js
index 7dc13e34d550a..3109f178edfec 100644
--- a/packages/adapter-node/index.js
+++ b/packages/adapter-node/index.js
@@ -9,7 +9,7 @@ const files = fileURLToPath(new URL('./files', import.meta.url).href);
 
 /** @type {import('.').default} */
 export default function (opts = {}) {
-	const { out = 'build', precompress, envPrefix = '' } = opts;
+	const { out = 'build', precompress, envPrefix = '', preservedRequestKeys = [] } = opts;
 
 	return {
 		name: '@sveltejs/adapter-node',
@@ -72,7 +72,8 @@ export default function (opts = {}) {
 					HANDLER: './handler.js',
 					MANIFEST: './server/manifest.js',
 					SERVER: `./server/index.js`,
-					ENV_PREFIX: JSON.stringify(envPrefix)
+					ENV_PREFIX: JSON.stringify(envPrefix),
+					PRESERVED_REQUEST_KEYS: JSON.stringify(preservedRequestKeys)
 				}
 			});
 		}
diff --git a/packages/adapter-node/src/handler.js b/packages/adapter-node/src/handler.js
index 26ad1324c0da7..d0c5f8e10e4cd 100644
--- a/packages/adapter-node/src/handler.js
+++ b/packages/adapter-node/src/handler.js
@@ -21,6 +21,8 @@ const body_size_limit = parseInt(env('BODY_SIZE_LIMIT', '524288'));
 
 const dir = path.dirname(fileURLToPath(import.meta.url));
 
+const preservedRequestKeys = JSON.parse('PRESERVED_REQUEST_KEYS');
+
 /**
  * @param {string} path
  * @param {boolean} client
@@ -54,6 +56,11 @@ const ssr = async (req, res) => {
 			request: req,
 			bodySizeLimit: body_size_limit
 		});
+
+		for (const key of preservedRequestKeys) {
+			// @ts-expect-error
+			request[key] = req[key];
+		}
 	} catch (err) {
 		res.statusCode = err.status || 400;
 		res.end('Invalid request body');