Dialyzer error: Function MyAppWeb.OpenApiSpex.Plug.RenderSpec.init/1 does not exist

[Nezteb]

Elixir: 1.14.0
Phoenix: 1.6.11

Following the docs exactly, I added the following to one of my router scopes like so:

scope "/api" do
  pipe_through :api
  resources "/users", MyAppWeb.UserController, only: [:create, :index, :show]
  get "/openapi", OpenApiSpex.Plug.RenderSpec, []
end

However, when running mix dialyzer, this gives an error:

> mix dialyzer
...
Total errors: 1, Skipped: 0, Unnecessary Skips: 0
done in 0m2.04s
lib/my_app_web/router.ex:28:unknown_function
Function MyAppWeb.OpenApiSpex.Plug.RenderSpec.init/1 does not exist.
________________________________________________________________________________
done (warnings were emitted)
Halting VM with exit status 2

I know this isn't actually the case, because RenderSpec.init/1 does exist when I CMD+click on it in my editor.

Dialyxir has a wiki page on using Dialyxir with Phoenix that mentions how to avoid spurious errors, but it's from 2019 and I don't know if any of it is required anymore.

Any ideas on what I might be doing incorrectly? 🤔

[mbuhot]

Notice the module name: MyAppWeb.OpenApiSpex.Plug.RenderSpec.init includes your own applications module MyAppWeb as a prefix.

That suggests there's a surrounding scope "/something", MyAppWeb do in your router.

If that's the case, changing it from scope/4 to scope/3 should fix it.

edit: Updated to obfuscate module names

[Nezteb]

Ah damn.

1. I didn't properly obfuscate the naming of my modules in this GH issue. 🤦‍♂️
2. In the initial PR description I had copy-pasted the code snippet from the open-api-spex docs instead of my actual app, when in reality my scope block was using a different arity and passing the web module. 🤦‍♂️
3. I didn't even realize that the initial mix phx.new I had ran generated:

  scope "/", MyAppWeb do
    pipe_through :browser

    get "/", PageController, :index
  end

Removing that module name and fully qualifying the controllers gets rid of the dialyzer error, thank you a ton!

It's probably not necessary, but would y'all accept a minor doc change PR to clarify that users adding open-api-spex might need to double check which version of scope they are using? 😅

[mbuhot]

It's probably not necessary, but would y'all accept a minor doc change PR to clarify that users adding open-api-spex might need to double check which version of scope they are using? 😅

Yes please!

[Nezteb]

Yes please!

Done! #507