Don't clean references on every file save

[crbelaus]

This pull request stops cleaning file references on every file save and, instead, cleans them only when we compile the file.

On the one hand we stop cleaning the file references on the TextDocumentDidSave notification. On the other hand we now clean the references on the :start event of the compiler tracer.

As per the Elixir docs:

:start - (since v1.11.0) invoked whenever the compiler starts to trace a new lexical context. A lexical context is started when compiling a new file or when defining a module within a function

Since this is only executed when compiling a file or defining a module we know that it is safe to to clean references at this point, since new ones will be populated during the compilation that just started.

The following video shows an example. Observe how the terminal at the bottom of the screen says "CLEANING REFERENCES FOR $FILE" when I update the file contents but doesn't do anything when I save without changing the file contents.

Screen.Recording.2023-08-16.at.19.51.36.mov

Closes #154

[crbelaus]

I added this only for the video, can be removed before merging.

[mhanberg]

One thing that I am unsure about with the :start trace is whether it is called only for a file, or if it is called multiple times if you define submodules or multiple modules in the same file

so, it should still work even if you have this code

# lib/foo.ex
defmodule Foo do
  defmodule Bar do
    def run() do
    end
  end

  def run() do
  end
end

or

# lib/foo.ex
defmodule Foo do
  def run() do
  end
end

defmodule Bar do
  def run() do
  end
end

[mhanberg]

spec is wrong

[crbelaus]

Ouch! Bad copy&paste 🤦‍♂️

[mhanberg]

i'm fairly certain this is just a file path already, so you don't have to parse it as a URI and then convert it back to a path again

[crbelaus]

You are right. I've just removed the unused URI.parse call

[mhanberg]

@dvic Cristian beat you to it 🤣

[dvic]

@dvic Cristian beat you to it 🤣

hah that's okay, did not start working on it

@crbelaus awesome job :)!

[crbelaus]

One thing that I am unsure about with the :start trace is whether it is called only for a file, or if it is called multiple times if you define submodules or multiple modules in the same file

so, it should still work even if you have this code

# lib/foo.ex
defmodule Foo do
  defmodule Bar do
    def run() do
    end
  end

  def run() do
  end
end

or

# lib/foo.ex
defmodule Foo do
  def run() do
  end
end

defmodule Bar do
  def run() do
  end
end

My understanding after reading the documentation is that in those scenarios the :start callback will be called only once, but I will verify it later today and report back.

On the other hand I have a question about this @mhanberg: should we clean up the symbols table as well as the references table?

[mhanberg]

I think the symbol purging is fine where it is, but I did put it where it is because I was un clear about how many times start is called.

[mhanberg]

but I will verify it later today and report back.

Thanks 🙇🏻

[crbelaus]

@mhanberg I've just checked an even when having two modules on the same file and having nested modules the start is only called once per file when any of its contents change.

[mhanberg]

Excellent