Should the Elixir formatter allow trailing commas?

Chat & Discussions Discussions
,
4

I think in macros, that is true, but not for lists, maps, or other collections. So that would be one thing consider if that is the case.

EDIT: The code examples in my first post all execute successfully in IEx.

Indeed, a macro with a trailing comma will raise a compilation error. For example, this code:

defmodule HelloPhoenix.Repo do
  use Ecto.Repo,
    otp_app: :hello_phoenix,
    adapter: Ecto.Adapters.Postgres,

  # ...
end

produces this error:

Compiling 1 file (.ex)

== Compilation error in file lib/hello_phoenix/repo.ex ==
** (SyntaxError) invalid syntax found on lib/hello_phoenix/repo.ex:4:36:
    error: unexpected expression after keyword list. Keyword lists must always come as the last argument. Therefore, this is not allowed:

        function_call(1, some: :option, 2)

    Instead, wrap the keyword in brackets:

        function_call(1, [some: :option], 2)

    Syntax error after: ','
    │
  4 │     adapter: Ecto.Adapters.Postgres,
    │                                    ^
    │
    └─ lib/hello_phoenix/repo.ex:4:36
3 Likes