vercel not running build and instal commands and not creating Serverless functions - node.js

Question

I am trying to move my application's API to Vercel. It is written in Typescript and uses Express.
The index.ts is located in <root>/src. The npm run build compiles it into <root>/dist directory. The file contains the following:
const app = express();
app.use((req: Request, res: Response, next: NextFunction) => {
//blah, blah, there is a lot going on here
})
app.use('/', common);
//... other app.use(s)
const port = process.env.PORT || 5000;
app.listen(port, () => console.log(`Server running on ${port}, http://localhost:${port}`));
module.exports = app;
I've got the following in the vercel.json file which is located in the root directory where the package.json also is:
{
"version": 2,
"installCommand": "npm install",
"buildCommand": "npm run build",
"outputDirectory": "dist",
"builds": [
{
"src": "dist/index.js",
"use": "#vercel/node"
}
],
"routes": [
{
"src": "/(.*)",
"dest": "dist/index.js"
}
]
}
When locally I run npm run build, then vercel dev --listen 5000 I get Ready! Available at http://localhost:5000 and can go to http://localhost:5000/ping and get a response.
Now I commit the files to git, the deployment runs, but judging by the logs the npm install and npm run build commands are not running. No functions are created my /ping endpoint returns "Page not found".
Here is the deployment log:
This is what Build & Development Settings look like (the Root Directory is left blank):
I followed several recommendations I found online and according to them everything should work. I probably miss some setting somewhere. What is it?
If more information is needed, please let me know, I'll update my question.
Thank you.
--- UPDATE ---
I have set the Root Directory to src and checked the "Include source files outside of the Root Directory in the Build Step" checkbox. Now the npm install and npm run build are executing. As you can see some static files are deployed, but there are still no serverless functions and my /ping route returns 404 and "home" page, i.e. / route returns the content of the index.js file. In addition the local is not working either anymore, also returning 404 now.
Without that checkbox I was getting
Warning: The vercel.json file should exist inside the provided root directory
and still no install or build running.
Also worth noting that I had to change my tsconfig.json to have "outDir": "src/dist" instead of "outDir": "dist", otherwise I was getting
Error: No Output Directory named "dist" found after the Build completed. You can configure the Output Directory in your Project Settings.
Removed the Root directory and back to square one, no npm commands running but local is working with / route returning Cannot GET / and /ping returning correct response.

Answer 1

For everyone out there who's looking for an answer, maybe this will help you.
In my case, what I needed is to create a folder, called api in my src folder, i.e. the folder that is specified as Root Directory in Build & Development Settings in Vercel. Within this directory, each serverless function needs a file named the same as the path of the route. For example, the file named "my-route.js" will be accessible via https://my-app-name.vercel.com/api/my-route.
All this file needs is an import of index.js file and module.exports. For example:
import app from '../index';
module.exports = app;
The index.js should also live the Root and contain your express setup.
If you want to have dynamic path parameters, the files' names in the api directory should be wrapped in square brakets, like [my-param.js]. You can also have sub-directories in the api foler.
Here are a few links that helped me figure this out:
https://dev.to/andrewbaisden/how-to-deploy-a-node-express-app-to-vercel-2aa
https://medium.com/geekculture/deploy-express-project-with-multiple-routes-to-vercel-as-multiple-serverless-functions-567c6ea9eb36
https://ryanccn.dev/posts/vercel-framework/#path-segments
No changes were needed in my existing Express setup and routes files.
Hope this will help someone. Took me quite a while to figure it all out :)