Elixir Internals: Return all references to a function on a specific line of a file

Questions / Help
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1

I am trying to add rename support to the wonderful Elixir Language Server project in https://github.com/JakeBecker/elixir-ls/issues/22. I’m at a very early stage in this work, making sure I understand the Language Server Protocol spec as well as the capabilities within Elixir itself, and creating a list of all the work I believe will be involved. That said I’ve been able to implement a proof of concept that, within certain constraints, does rename function definitions and references.

I’m facing a challenge currently and am posting here in the hopes that someone can save me some time and point me in the right direction in the Elixir code base.

When I need to rename a function, I first find the function definition and all references to the function throughout the project’s code base. The granularity of this information (in part coming from Mix.Tasks.Xref) currently only includes files and line numbers. I don’t know the function name start and end character numbers on the given line, how many times the function is referenced on that line, or exactly what names are used for those references, be they fully qualified modules and function names, partially qualified modules relying on aliases, module names that rely on aliases with renamed modules via the :as keyword, or just function names via import. This makes it challenging to know what portion of text on the given line needs to be renamed.

It seems to me that I need to tap into the Elixir runtime in order to know exactly what valid ways exist to reference a given function on a given line of a file. Without tapping into the runtime it seems that I would have to reimplement a bunch of logic that would have already been implemented in Elixir itself.

Does that make sense? So what I’m hoping for is a function I can call where I can pass in an MFA tuple, a file path and a line number and get back a list of references to that function on that line along with metadata about those references so I can determine the exact start and end characters that need to be renamed.

From my initial research I’m assuming this at least doesn’t exist today in a public function, but perhaps there are internals I can use, and if so perhaps this is worth a proposal for a new public function to help with Elixir tooling.

Thanks in advance for any tips you can provide.

5 Likes
2

Hi @justincjohnson!

If you set up ElixirLS to use this branch of ElixirSense, you’ll have everything you need. You can use ElixirSense.references/3 to retrieve the list of all references including function calls from aliased/imported modules. You’ll also get the exact ranges you need to replace in each file. Here’s an example:

iex> ElixirSense.references(code, line, column) |> Enum.take(2)
  [
    %{
      uri: "test/support/modules_with_references.ex",
      range: %{
        start: %{line: 26, column: 60},
        end: %{line: 26, column: 64}
      }
    },
    %{
      uri: "test/support/modules_with_references.ex",
      range: %{
        start: %{line: 42, column: 16},
        end: %{line: 42, column: 20}
      }
    }
  ]
8 Likes
3

Wonderful! I’ll give it a try over the weekend and let you know if I have any feedback.

2 Likes
4

Forgive me for the delay @msaraiva. I’ve run into some trouble with the code but haven’t had time to formulate a simplified reproduction to ensure it doesn’t have to do with anything specific to my ElixirLS changes. I’ll keep you posted.

5

Hey @justincjohnson, no worries. The branch mentioned has already been merged so it’s probably a good idea to start using master for your tests.