Replace unknown remote function

[sheldak]

I've prepared that PR to propose extending code actions by replacing unknown remote functions. For example, the following code:

defmodule Example do
  def foo do
    var = Enum.counts([2, 3])
  end
end

contains an unknown function: counts/1. After this change, we would get 2 possible Quick Fixes:

Replace unknown function with 'Enum.concat'
Replace unknown function with 'Enum.count'

that rewrite our code to:

defmodule Example do
  def foo do
    var = Enum.concat([2, 3])
  end
end

or

defmodule Example do
  def foo do
    var = Enum.count([2, 3])
  end
end

respectively.

In our example, Quick Fixes were generated from the following Elixir warning:

Enum.counts/1 is undefined or private. Did you mean:

      * concat/1
      * concat/2
      * count/1
      * count/2

I find such a feature very convenient, so I'm waiting for comments and feedback.

[lukaszsamson]

Nice work @sheldak . The problem with that approach is that it's error prone. We recently had to revert a similar text based code transformation (#775). A better option would be to express the code changes in terms of AST transformations. See #773

[sheldak]

@lukaszsamson thanks for the update! So I will wait with contributing until #773 is merged.

[scohen]

@sheldak #773 has landed.

[sheldak]

@scohen That's great! I will definitely come back to this feature soon

[sheldak]

@scohen I've updated that so now it should fit the new way of doing code actions

[scohen]

nit: meta1 and meta2 are not descriptive names, one is the function call meta and the other is the module meta. Suggest function_meta and module_meta

[scohen]

this exposes private implementation details, I have an example of how to handle this without doing so below.

[scohen]

nit, module isn't actually a module, it's a list, and it will be missing the leading Elixir that all elixir modules have.

[scohen]

nit: Pattern is a much less descriptive name than variable_re, but we should not be exposing this anyways.

[scohen]

Actually, I'm matching against the Types.Diagnostic module in the extract_line
It's better to do it in apply, you wrote a typespec, so why not:

def apply(%SourceFile{} = source_file, %Diagnostic{} = diagnostic) do 
...
end

it seems like none of the keys in diagnostic.range.start.line have an optional type, so why isn't it guaranteed that one_based_line is an integer

Because elixir is a dynamic language and there are no types.

What I'm saying is: move one_based_line out of the with statement.

[scohen]

then this is just

module_string = Enum.map_join(module_list, ".", &Atom.to_string/1)

[sheldak]

I've found out that replacing wasn't working if the module of the function to replace was aliased. Fixed in the second commit (9a01a18).

[scohen]

One more comment regarding the tests, and we're good to merge

[scohen]

wow, this works very well; I think the structural == will even work with documents. Very nice.