Add Fetch Does Not Work In API Serverless Function as a Next.js TIL

README.md

@@ -10,7 +10,7 @@ pairing with smart people at Hashrocket.
 
 For a steady stream of TILs, [sign up for my newsletter](https://crafty-builder-6996.ck.page/e169c61186).
 
-_1398 TILs and counting..._
+_1399 TILs and counting..._
 
 ---
 
@@ -621,6 +621,7 @@ _1398 TILs and counting..._
 
 - [Create Files And Directories For Dynamic Routes](nextjs/create-files-and-directories-for-dynamic-routes.md)
 - [Define URL Redirects In The Next Config](nextjs/define-url-redirects-in-the-next-config.md)
+- [Fetch Does Not Work In API Serverless Function](nextjs/fetch-does-not-work-in-api-serverless-function.md)
 - [Make Environment Variable Publicly Available](nextjs/make-environment-variable-publicly-available.md)
 - [Match Middleware On Groups Of Paths](nextjs/match-middleware-on-groups-of-paths.md)
 - [Push A Route With A URL Object](nextjs/push-a-route-with-a-url-object.md)

nextjs/fetch-does-not-work-in-api-serverless-function.md

@@ -0,0 +1,24 @@
+# Fetch Does Not Work In API Serverless Function
+
+Next.js ships with [its own implementation of
+`fetch`](https://nextjs.org/docs/app/api-reference/functions/fetch) that
+extends the [native `fetch`
+API](https://developer.mozilla.org/en-US/docs/Web/API/Fetch_API).
+
+I ran into a bug recently that was only reproducible in production. I had a
+Next.js API function that was `POST`ing to another API endpoint using `fetch`.
+I tested it several ways in development. It worked great. However, once the
+feature was in production, it was silently failing. After some `console.log`
+debugging, I discovered that the target API was getting an empty `body` in the
+`POST` request.
+
+I don't know the specifics of why, but somehow the `fetch` implementation
+running in the Vercel serverless function environment apparently strips out the
+`body` of a POST request.
+
+The solution, for me, was to add the
+[`node-fetch`](https://github.com/node-fetch/node-fetch) package and import
+that version of fetch in my API function. Once I made that change, my feature
+was working again.
+
+[source](https://github.com/vercel/vercel/discussions/4971)