INN-1087 Add edge streaming support to all serve handlers (#163)

## Summary INN-1087

Adds the ability for the SDK to stream responses back to Inngest,
enabling longer timeouts in edge runtimes such as Deno, Cloudflare, or
Next.js.

- **Add edge streaming support**
> We're currently very strict about streaming support, only allowing it
for `"inngest/next"`, ensuring users must opt in using
`allowEdgeStreaming: true` and only allowing Next.js projects on Vercel.
  >
> Following this being tested in production for a while, streaming
support for other supported platforms is trivial to add, just writing
code to turn it on.
- **Add support for Next.js Edge Functions**
> The `"inngest/next"` handler now supports both Serverless Functions
and Edge Functions; users can switch between both using Next.js
conventions without having to change any of our code or imports.
- **Add support for Next.js 13+ [Route
Handlers](https://beta.nextjs.org/docs/routing/route-handlers)**
> Ended up wanting this as part of testing; if folks are using
edge/streaming then it feels more likely that they're happy to use a
beta version of Next.js itself too, so we might as well support this.
  > 
> Route handlers use the same `"inngest/next"` serve handler, but users
must export differently:
  > ```ts
  > export default serve(...);
  > // to
  > export const { GET, POST, PUT } = serve(...);
  > ```

## Related

- inngest/inngest#429

.changeset/violet-tools-watch.md

@@ -0,0 +1,5 @@
+---
+"inngest": minor
+---
+
+INN-1087 Add edge streaming support to `"inngest/next"` serve handler

etc/inngest.api.md

@@ -114,20 +114,22 @@ export class Inngest<Events extends Record<string, EventPayload> = Record<string
 }
 
 // Warning: (ae-forgotten-export) The symbol "Handler_2" needs to be exported by the entry point index.d.ts
+// Warning: (ae-forgotten-export) The symbol "ActionResponse" needs to be exported by the entry point index.d.ts
 //
 // @public
-export class InngestCommHandler<H extends Handler_2, TransformedRes> {
+export class InngestCommHandler<H extends Handler_2, TResTransform extends (res: ActionResponse<string>, ...args: Parameters<H>) => any, TStreamTransform extends (res: ActionResponse<ReadableStream>, ...args: Parameters<H>) => any> {
     constructor(
     frameworkName: string,
     appNameOrInngest: string | Inngest<any>,
-    functions: InngestFunction<any, any, any>[], { inngestRegisterUrl, fetch, landingPage, logLevel, signingKey, serveHost, servePath, }: RegisterOptions | undefined,
+    functions: InngestFunction<any, any, any>[], { inngestRegisterUrl, fetch, landingPage, logLevel, signingKey, serveHost, servePath, streaming, }: RegisterOptions | undefined,
     handler: H,
-    transformRes: (actionRes: ActionResponse, ...args: Parameters<H>) => TransformedRes);
+    transformRes: TResTransform,
+    streamTransformRes?: TStreamTransform);
     // Warning: (ae-forgotten-export) The symbol "FunctionConfig" needs to be exported by the entry point index.d.ts
     //
     // (undocumented)
     protected configs(url: URL): FunctionConfig[];
-    createHandler(): (...args: Parameters<H>) => Promise<TransformedRes>;
+    createHandler(): (...args: Parameters<H>) => Promise<Awaited<ReturnType<TResTransform>>>;
     protected readonly frameworkName: string;
     readonly handler: H;
     protected _isProd: boolean;
@@ -157,8 +159,11 @@ export class InngestCommHandler<H extends Handler_2, TransformedRes> {
     protected signingKey: string | undefined;
     // (undocumented)
     protected signResponse(): string;
-    // Warning: (ae-forgotten-export) The symbol "ActionResponse" needs to be exported by the entry point index.d.ts
-    readonly transformRes: (res: ActionResponse, ...args: Parameters<H>) => TransformedRes;
+    // (undocumented)
+    protected readonly streaming: RegisterOptions["streaming"];
+    // (undocumented)
+    readonly streamTransformRes: TStreamTransform | undefined;
+    readonly transformRes: TResTransform;
     // (undocumented)
     protected validateSignature(sig: string | undefined, body: Record<string, unknown>): void;
 }
@@ -200,6 +205,7 @@ export interface RegisterOptions {
     serveHost?: string;
     servePath?: string;
     signingKey?: string;
+    streaming?: "allow" | "force" | false;
 }
 
 // @public

package.json

@@ -35,7 +35,8 @@
     "build:landing": "cd landing && yarn run build",
     "build:check": "api-extractor run --verbose",
     "build:copy": "cp package.json LICENSE.md README.md CHANGELOG.md dist",
-    "prelink": "yarn run build:copy"
+    "prelink": "yarn run build:copy",
+    "local:pack": "yarn build && yarn prelink && yarn pack --verbose --frozen-lockfile --filename inngest.tgz --cwd dist"
   },
   "homepage": "https://github.com/inngest/inngest-js#readme",
   "repository": {

src/cloudflare.ts

@@ -3,8 +3,9 @@ import {
   ServeHandler,
 } from "./components/InngestCommHandler";
 import { headerKeys, queryKeys } from "./helpers/consts";
+import type { SupportedFrameworkName } from "./types";
 
-export const name = "cloudflare-pages";
+export const name: SupportedFrameworkName = "cloudflare-pages";
 
 /**
  * In Cloudflare, serve and register any declared functions with Inngest, making

src/components/Inngest.ts

@@ -2,6 +2,7 @@ import { envKeys } from "../helpers/consts";
 import { devServerAvailable, devServerUrl } from "../helpers/devserver";
 import {
   devServerHost,
+  getFetch,
   inngestHeaders,
   isProd,
   processEnv,
@@ -134,24 +135,7 @@ export class Inngest<
       inngestEnv: env,
     });
 
-    this.fetch = Inngest.parseFetch(fetch);
-  }
-
-  /**
-   * Given a potential fetch function, return the fetch function to use based on
-   * this and the environment.
-   */
-  private static parseFetch(fetchArg: FetchT | undefined): FetchT {
-    if (fetchArg) {
-      return fetchArg;
-    }
-
-    if (typeof fetch !== "undefined") {
-      return fetch;
-    }
-
-    // eslint-disable-next-line @typescript-eslint/no-var-requires
-    return require("cross-fetch") as FetchT;
+    this.fetch = getFetch(fetch);
   }
 
   /**