List of regex in module attributes do not emit a warning in Elixir 1.19

[Gladear]

Elixir and Erlang/OTP versions

Erlang/OTP 27 [erts-15.2.3] [source] [64-bit] [smp:12:12] [ds:12:12:10] [async-threads:1] [jit]

Elixir 1.19.0-dev (8b79681) (compiled with Erlang/OTP 27)

Operating system

MacOS

Current behavior

✅ When a regex is stored in a module attribute and used in a function body, a warning it emitted.
❌ When it's stored in a list, map, or anything, nothing is being emitted.

defmodule Foo do
  @regex ~r/hello/
  @list_regex [~r/hello/, ~r/world/]

  def use do
    Regex.match?(@regex, "use")
    Enum.any?(@list_regex, &Regex.match?(&1, "use"))
  end
end

# only the first @ emits
warning: storing and reading regexes from module attributes is deprecated, inline the regex inside the function definition instead
└─ iex:6: Foo.use/0

Expected behavior

I would have expected all regexes placed in module attributes to emit a warning, as, as far as I understand, those in arrays will cause an issue in OTP 28 too.

I see the warning is emitted when the module attribute is used, which may explain why it does not occur for lists or maps of regexes. Should it be moved to the module attribute declaration?

[josevalim]

The warning is emitted so we have fewer crashes but we may not be able to get rid of all of them. I will see if there is something that can be done about lists but there may still be other cases.

[sabiwara]

Yeah I know I've been using lists of tuples with regexes, and maybe maps are a thing too.
But if we really want to address this, should we do it in :elixir_quote.escape with a new :module_attr kind or sth?

[josevalim]

Good call, I think :elixir_quote is the way to go indeed, I went ahead and improved the error message there, with the initial going of surfacing those incompatibilities so we can assess how common the idiom is.