feat(transport): Make SvelteKit adapter deployable on Netlify Edge Functions

transport/.gitignore

@@ -136,4 +136,6 @@ edge-light.js
 edge-light.d.ts
 index.js
 index.d.ts
+svelte.js
+svelte.d.ts
 test/*.js

transport/package.json

@@ -26,6 +26,7 @@
   "types": "./index.d.ts",
   "exports": {
     "bun": "./bun.js",
+    "svelte": "./svelte.js",
     "edge-light": "./edge-light.js",
     "default": "./index.js"
   },

transport/svelte.ts

@@ -0,0 +1,79 @@
+// This entire workaround is to make SvelteKit run on Netlify Edge Functions
+// which execute in an old version of Deno that doesn't support some `node:*`
+// imports, such as `node:assert`. This makes the undici import fail when we try
+// to use `@connectrpc/connect-node`.
+//
+// By making these dynamic imports, we can await them inside of the `unary` or
+// `stream` function calls to figure out which client we are using.
+
+export function createTransport(baseUrl: string) {
+  const web = import("@connectrpc/connect-web").then(
+    ({ createConnectTransport }) => {
+      // The Connect Node client doesn't work on edge runtimes: https://github.com/bufbuild/connect-es/pull/589
+      // so set the transport using connect-web. The interceptor is required for it work in the edge runtime.
+      return createConnectTransport({
+        baseUrl,
+        interceptors: [
+          /**
+           * Ensures redirects are followed to properly support the Next.js/Vercel Edge
+           * Runtime.
+           * @see
+           * https://github.com/connectrpc/connect-es/issues/749#issuecomment-1693507516
+           */
+          (next) => (req) => {
+            req.init.redirect = "follow";
+            return next(req);
+          },
+        ],
+        fetch,
+      });
+    },
+  );
+  const node = import("@connectrpc/connect-node").then(
+    ({ Http2SessionManager, createConnectTransport }) => {
+      // We create our own session manager so we can attempt to pre-connect
+      const sessionManager = new Http2SessionManager(baseUrl, {
+        // AWS Global Accelerator doesn't support PING so we use a very high idle
+        // timeout. Ref:
+        // https://docs.aws.amazon.com/global-accelerator/latest/dg/introduction-how-it-works.html#about-idle-timeout
+        idleConnectionTimeoutMs: 340 * 1000,
+      });
+
+      // We ignore the promise result because this is an optimistic pre-connect
+      sessionManager.connect();
+
+      return createConnectTransport({
+        baseUrl,
+        httpVersion: "2",
+        sessionManager,
+      });
+    },
+  );
+
+  return {
+    async unary(
+      ...args: [any, any, any, any, any, any, any]
+    ): Promise<unknown> {
+      let client;
+      try {
+        client = await node;
+      } catch {
+        client = await web;
+      }
+
+      return client.unary(...args);
+    },
+    async stream(
+      ...args: [any, any, any, any, any, any, any]
+    ): Promise<unknown> {
+      let client;
+      try {
+        client = await node;
+      } catch {
+        client = await web;
+      }
+
+      return client.stream(...args);
+    },
+  };
+}

transport/tsconfig.json

@@ -1,4 +1,4 @@
 {
   "extends": "@arcjet/tsconfig/base",
-  "include": ["bun.ts", "edge-light.ts", "index.ts"]
+  "include": ["bun.ts", "edge-light.ts", "index.ts", "svelte.ts"]
 }