Enable or document shared formats

[nathanl]

The docs show using formats like this:

attribute :uuid, :string,  format: ~r/\A\d{5}\-\d{5}\-\d{5}\-\d{5}\-\d{5}\z/

When multiple schemas use a uuid of that format, it would be less error-prone to be able to do something like:

attribute :uuid, :string,  format: Formats.uuid()

I don't see anything like this in the docs. Is it supported? If not, could it be?

So far I've attempted to use a separate module and ensure that it's compiled before the schema using require, @before_compile, and elixirc_paths, but I always get an error saying that the module is unavailable. Maybe this is because the Speck compiler runs before any of the Mix.compilers?

[amclain]

I don't see anything like this in the docs. Is it supported? If not, could it be?

We plan to support this is with custom attribute types, which is a feature in the backlog. I've documented it in this repo as issue #11.

A workaround to do what you wrote is to use Code.require_file in your spec:

Code.require_file "../lib/format.ex"

struct Example.Message

attribute :uuid, :string, format: Format.uuid

defmodule Format do
  def uuid do
    ~r/\A\d{5}\-\d{5}\-\d{5}\-\d{5}\-\d{4}\z/
  end
end

Please continue this thread if you run into any other issues with this approach.

[amclain]

Functionality will be covered by #11

[nathanl]

Code.require_file "../lib/format.ex" does not work because the Speck compiler ignores it as unknown syntax here.

[amclain]

Another workaround is to make the Format module a dependent library. It could be as simple as a path dependency in the same repo. That will cause the Format module to be compiled first, then Speck protocols, then the application code. This route also doesn't require adding any code to the header of the specs.