Dev-only routes

laurenfackler

To quickly test changes to email template copy and styling, I created a couple routes that are only accessible in the dev environment:

if Mix.env() == :dev do
  get("/email_previews", EmailPreviewController, :index)
  get("/email_previews/:email", EmailPreviewController, :show)
end

However, this now means that there is a template file that references a path helper function that doesn’t exist in other environments:

<ul>
<%= for email <- @emails do %>
  <li><a href="<%= email_preview_path(@conn, :show, to_string(email)) %>"><%= email %></a></li>
<% end %>
</ul>

which prevents the app from compiling:

** (CompileError) lib/my_app_web/templates/email_preview/index.html.eex:9: undefined function email_preview_path/3

How can I get the app to compile?

16 comments

/phoenix #environment #routerhelpers

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2019-12-03 02:01:03 UTC

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aptinio

Try wrapping the for loop in a if Mix.env() == :dev block.

Post #1

benwilson512

Author of Craft GraphQL APIs in Elixir with Absinthe

You don’t want to do Mix.env calls at runtime. Does the email_preview_path exist in a view that only is needed in dev?

Post #2

aptinio

Oh, right! I guess it’s different for routes because they’re compiled?

Post #3

benwilson512

Author of Craft GraphQL APIs in Elixir with Absinthe

Right, the if Mix.env == :dev do call in the router happens at compile time because it’s in the module body.

Post #4

laurenfackler

Yes, it only exists in a template that’s needed in dev.

Post #5

andrejsm

Simply don’t use the compiled path functions. Instead type them as strings and interpolate values.

Post #6

danschultzer

Pow Core Team

You could use Mix.env == :dev at compile time:

<ul>
<%= if unquote(Mix.env() == :dev),
  do: for email <- @emails do %>
  <li><a href="<%= email_preview_path(@conn, :show, to_string(email)) %>"><%= email %></a></li>
<% end %>
</ul>

Post #7

mudasobwa

Creator of Cure

When one needs different modules to be compiled in different environments, it’d be better to explicitly define these module sets, instead of polluting the source code with conditionals.

For the modules to be available in :test only, the common approach is to create test/support folder, and modify your mix.exs in the following way:

Create a private function like this:

defp elixirc_paths(:test), do: ["lib", "test/support"]
defp elixirc_paths(_), do: ["lib"]

Modify your Mix.Project.project/0 callback to include the following key/value pair:

elixirc_paths: elixirc_paths(Mix.env())

Put all the files containing modules needed only in test environment there.

That way all of them will be compiled in test and discarded in all other environments.

If you need some modules to exist in :prod only, declare compile paths appropriately.

Post #8

laurenfackler

I literally laughed out loud and then facepalmed after reading your suggestion. Thanks!

Post #9

laurenfackler

I ended up going with the solution suggested by @andrejsm but I did give this a try out of curiosity and couldn’t get it to work. At first, I was getting a syntax error, so I switched to a multi-line if statement to see if that was the cause—that fixed the syntax error but resulted in the same compile error about the path function not being available.

Post #10

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