How to change a module's source file attribute?

Questions / Help
1

A module X in file /project/lib/x.ex has the following module metadata:

iex(7)> X.module_info()
[
  module: X,
  exports: [__info__: 1, foo: 0, module_info: 0, module_info: 1],
  attributes: [vsn: [259318855844826186809719652690816251721]],
  compile: [
    version: '7.3.1',
    options: [:dialyzer, :no_spawn_compiler_process, :from_core,
     :no_auto_import],
    source: '/project/lib/x.ex'
  ],
  native: false,
  md5: <<195, 22, 254, 181, 205, 81, 155, 43, 204, 133, 244, 77, 11, 5, 183,
    73>>
]

How can one modify the source entry to something else than the name of the file where module X is defined?

I tried

defmodule X do
@compile {:source, "/project/lib/another_file.ex"}
def foo, do: IO.puts "foo"
end

but this has no effect.

Thanks

2

@file if I recall correctly. But it’s meant to be used for generated files only, as well as @line.

3

@file works on a function basis, not for the whole module unfortunately.

4

The closes I know is to strip the beam.

:beam_lib.strip_files(["Elixir.X.beam"]).

Honestly though I’m not sure why you would want to manipulate the source compile attribute. source and vsn are 2 quick checks in production that you are running the modules you think you should be running.

1 Like
5

I want to manipulate it in generated modules, not in those written by hand of course.

6

The solution might be to use Module.create explicitly instead of using defmodule - you can alter the file in the environment passed in there.

7

I thought about that but there are issues.

For example, if we do like this

q = quote do
def foo, do: 1/0
def bar, do: 2/0
end
Module.create(Y, q, Map.put(__ENV__, :file, "y.ex"))

then when calling Y.foo() and Y.bar() the lines in the stracktraces are the same. I think this is because quote does not add metadata line: number in this case (only when the quotes are generated by the compiler when calling macros do they get the line: number metadata).

I also tried to do quote location: :keep do ... but then the file is the physical file, not y.ex.

The only solution I found is to do Macro.postwalk to add the metadata keep: {"y.ex", number} on every node that has the metadata line: number.

This solution is working well, but a more direct way would be preferable. The possibilities are:

  1. have @file set the file for all following functions and macros, not only the next one

  2. support quote location: "filepath" do and quote lines: true do

In fact, I think both points 1) and 2) would be useful for my and other use cases.

8

quote doesn’t, but calling a macro with AST does.

9

Yep, that’s what I said (unless I expressed myself badly :smile:)

10

Just clarifying that quoting into something is not the same as building Macro’s in Elixir (which is oddly different from other languages). ^.^;