Repository: vercel/next.js
Pull request: fix: Ensure typegen CLI command doesn't hang due to open handles

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### What?

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Closes NEXT-
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### What?

Running `next typegen` can hang even after `✓ Route types generated successfully` prints.

```
Generating route types...
Using vars defined in .dev.vars
✓ Route types generated successfully
...
```

### Why?

 This is very problematic when needing to run `typegen` before `tsc` on CI. If the command hangs, then `tsc` never starts.

### How?

`next build` has the same potential issue and it works around this by waiting for the promise to resolve and then calling `process.exit(0)`. I copied this same solution over to the `typegen` command.

Changed files:
filename: packages/next/src/bin/next.ts
patch: @@ -395,8 +395,10 @@ program
     )}`
   )
   .action((directory: string, options: NextTypegenOptions) =>
+    // ensure process exits after typegen completes so open handles/connections
+    // don't cause process to hang
     import('../cli/next-typegen.js').then((mod) =>
-      mod.nextTypegen(options, directory)
+      mod.nextTypegen(options, directory).then(() => process.exit(0))
     )
   )
   .usage('[directory] [options]')

filename: test/e2e/app-dir/typed-routes/next.config.js
patch: @@ -1,3 +1,6 @@
+// intervals/open connections shouldn't block typegen from exiting
+setInterval(() => {}, 250)
+
 /**
  * @type {import('next').NextConfig}
  */

filename: test/e2e/app-dir/typed-routes/typed-routes.test.ts
patch: @@ -1,4 +1,5 @@
 import { nextTestSetup } from 'e2e-utils'
+import { runNextCommand } from 'next-test-utils'
 
 const expectedDts = `
 type AppRoutes = "/" | "/_shop/[[...category]]" | "/dashboard" | "/dashboard/settings" | "/docs/[...slug]" | "/gallery/photo/[id]" | "/project/[slug]"
@@ -90,4 +91,12 @@ type InvalidRoute = RouteContext<'/api/users/invalid'>`
       )
     })
   }
+
+  it('should exit typegen successfully', async () => {
+    const { code } = await runNextCommand(['typegen'], {
+      cwd: next.testDir,
+    })
+
+    expect(code).toBe(0)
+  })
 })