How to get function definition file and line?

What exactly you are trying to achieve? You may look into ElixirLS sources how they do it.

I would like to create a mix task, taking one of my website url, and that would output the file and the line of the controller function that is called by that url. I am tired of going to the router file, see which module and function is called by the route, go that module and look for the corresponding function.

You can try to extract that information from the Code.fetch_docs/1. It will not always be 100% precise (as if there is documentation, then it will point to the line for documentation), but works well enough, especially in presence of multiple heads.

Phoenix.Router — Phoenix v1.6.6 can give you the plug / plug_opts (action). But MyController.action/2 can be overwritten, so you cannot be sure that MyController, :index actually calls MyController.index/2.

In my case, I don’t think there is any overwriting, so that would be good enough!
I found how to get the module and function name with Phoenix.Router.route_info.
Code.fetch_docs/1 seems to be giving the line number in the file (thanks @hauleth ), I am just missing the name of the file

It is in the metadata of module itself. Just check out module.module_info().

Thanks, I have all the information I need
Phoenix.Router.route_info to know which module + function is called
module.module_info() for the source file path
Code.fetch_docs/1 for the line number

It deserve a blog post, once you have clear solution, if you have time

@ambareesha7 No blog post, but I made a PR on Phoenix that just got merged!
https://github.com/phoenixframework/phoenix/pull/4748

This is intersting. I’m wondering it this could also show all the places the route is referenced (with verified routes).