Elixir compiler: Having a @some_name in a @moduledoc gives a warning

Questions / Help
1

Havin this @moduledoc:

@moduledoc """
  Weekly schedule - extended version for admins, managers and users.

  ## Examples
  
  <div class={"flex #{if @is_home, do: ~c"home"}"}> for inline conditionals (for example for class names) inside elixir templates, maybe this will be helpful to someone
  """

the compiler gives following warning:

warning: undefined module attribute @is_home, please remove access to @is_home or explicitly set it before access
  lib/backend_web/live/components/week_live.ex:7

How comes the html example is considered (somehow) as code?
Is it working as designed and I’m doing something wrong??

2

It’s because of the #{} in the code, it starts interpolating in the string (delimited with """).

Try something like

@moduledoc ~S"""
...
"""

That should prevent interpolation inside the string (~S is a sigil for string without interpolation).

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3

@Nicd Thank you!

Though I did not expect to see any kind of interpolation happening in a @moduledoc string

4

""" is simply a plain ol’ heredoc delimiter which allows interpolation. It would be far more surprising to give """ special meaning in a core language feature. It doesn’t even have to be a heredoc, just anything that returns a string (or false or a keyword list but that is tangential to this point). This has utility as it means we can dynamically generate all or parts of it. There is a good example here.

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5

Well, I thought it is a core language feature…
Thanks for clarifying

6

It is, that’s what I’m saying. Heredocs allow interpolation unless you use ~S as @Nicd pointed out. I’m saying it would be weird for the core language feature of @moduledoc to treat them differently, is all.

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7

not really… """ is a multiline string, it isn’t suppose to denote documentation neither to only be used in documentation. I guess using the term heredoc in this case is what is making your explanation confusing. :thinking:

8

I use the terms “heredoc” and “multi-line string” interchangeably, as do parts of the Elixir documentation. The term “heredoc” has nothing to do with documentation and I certainly wasn’t trying to imply that it did by calling it that. In fact I was trying to imply the exact opposite but clearly failed.

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9

i know the term heredoc from other langs but i thought elixir always used multiline string for that purpouse :thinking:
like here

10

I probably misremembered about how much I’d seen it in the docs. I only see it in a couple of places in hexdocs and elixir-lang.org has a line:

Sigils also support heredocs, that is, three double-quotes or single-quotes as separators:

In any event, I still call 'em heredocs but I guess I should stop that when talking about them 'round here though this is the first time this has happen :sweat_smile: My point was trying to convey to OP to help with their confusion was that """ isn’t special to @moduledoc or any other module attributes.

2 Likes
11

TIL i can do something like that

~w"""
some_atom
another_atom third_atom
yet_another
"""a
1 Like