feat(gatsby): test redirects (#31011)

* feat(gatsby): test redirects

* Fix test

* refine message

* another error tweak

* actually fix test

Author: KyleAMathews

integration-tests/functions/src/api/redirect-me.ts

@@ -0,0 +1,8 @@
+import { GatsbyAPIFunctionResponse, GatsbyAPIFunctionRequest } from "gatsby"
+
+export default function topLevel(
+  req: GatsbyAPIFunctionRequest,
+  res: GatsbyAPIFunctionResponse
+) {
+  res.redirect(`/`)
+}

integration-tests/functions/test-helpers.js

@@ -212,6 +212,14 @@ export function runTests(env, host) {
       })
     })
 
+    describe(`functions can redirect`, () => {
+      test(`normal`, async () => {
+        const result = await fetch(`${host}/api/redirect-me`)
+
+        expect(result.url).toEqual(host + `/`)
+      })
+    })
+
     // TODO figure out why this gets into endless loops
     // describe.only(`hot reloading`, () => {
     // const fixturesDir = path.join(__dirname, `fixtures`)

packages/gatsby/src/internal-plugins/functions/gatsby-node.ts

@@ -364,7 +364,11 @@ export async function onCreateDevServer({
           await Promise.resolve(fnToExecute(req, res))
         } catch (e) {
           reporter.error(e)
-          res.sendStatus(500)
+          res
+            .status(500)
+            .send(
+              `Error when executing function "${functionObj.originalFilePath}": "${e.message}"`
+            )
         }
 
         const end = Date.now()