Hi Łukasz, your code is using knowledge that "require" puts the compilation of the requiring module on hold until the required module is compiled.
Even though "require" has this effect, it should not be used in the way you do. At least, what I understand from here <https://elixir-lang.org/getting-started/alias-require-and-import.html#require> is that "require" is meant to bring other module's defined macros into the compilation context of the current module, and nothing more, so I think it should be used only with this intent, and not for the purpose of what your code shows. (Hint: For what your code wants to do, you should be using "Code.ensure_loaded" or "Code.ensure_compiled", but never "require" to simply get its side-effect when you are not calling anything from module A). As such, and like already done for its cousin "import" and "alias", which are meant to facilitate access to the definitions in other modules, "require" should be returning a warning when a required module's definitions are not being used, otherwise it seems that "require" is being somehow treated like a second-citizen, regarding "import" and "alias", in the Elixir world, which to me would be "strange". I think this is something for the Elixir core team to decide: if they want "require" to stay as it is now, or if they want to provide consistent behavior with "import" and "alias" when nothing required is being used. Regards Mário segunda-feira, 8 de Abril de 2019 às 10:37:25 UTC+1, Łukasz Niemier escreveu: > > The problem is that `import` does more, and you can detect that `import` > is unused and it can be replaced by `require`, but compiler cannot reason > that `require` is unneeded as for example imagine that we have 2 modules > (in separate files, as this will not work within single file): > > defmodule A do > def foo, do: 10 > end > > And in second file > > defmodule AllFoos do > require A > > @foos for module <- :code.all_loaded(), function_exported?(module, :foo, > 0), do: module > > def foos, do: @foos > end > > And without that `require` this code will depend on compilation order > (which isn’t guaranteed by Elixir compiler) to work properly. So as you can > see the compiler has no knowledge whether it can alter compilation order > restricted by user. > > Of course this is highly unlike scenario for `require`, but is perfectly > valid code right now, with very well defined behaviour. > > Wiadomość napisana przez Mário Guimarães <mario.lui...@gmail.com > <javascript:>> w dniu 08.04.2019, o godz. 11:22: > > Lukasz, > > it should be possible to warn on unused "require". > > The thing is that "import" does what "require" does plus much more, and > still the compiler warns on unused "import". Check this by playing with > this code > > defmodule X do > def foo, do: " hello" > defmacro xpto, do: "Hey" > end > > defmodule Y do > import X > #require X > #def bar, do: X.xpto() <> X.foo() <> " world" > end > > Regards > Mário > > > segunda-feira, 8 de Abril de 2019 às 09:45:28 UTC+1, Łukasz Niemier > escreveu: >> >> You do not need to use macro to require compilation. You can use function >> or even just depending on fact that this module is already compiled in some >> highly hacky code with metaprogramming. I cannot give you any reasonable >> example right now. Also remember that you can require something just to >> call functions during compile time, it do not need to be macro. >> >> Wiadomość napisana przez Louis Pilfold <lo...@lpil.uk> w dniu >> 08.04.2019, o godz. 10:39: >> >> Hey >> >> Wouldn't it be possible to track if any macros have been used by the >> requiring module? I'm not familiar with the compiler here but it seems like >> it is always possible as all information is available at compile time. >> >> Cheers, >> Louis >> >> On Mon, 8 Apr 2019, 09:19 Łukasz Niemier, <luk...@niemier.pl> wrote: >> >>> Not possible as `require`s are *always* used - by the compiler, as this >>> marks that required module need to be compiled before compilation of module >>> with require. >>> >>> W dniu piątek, 5 kwietnia 2019 17:48:56 UTC+2 użytkownik Mário Guimarães >>> napisał: >>>> >>>> Hi, >>>> >>>> I suggest for Elixir to warn on unused requires, like it does for >>>> unused aliases. >>>> >>>> Thanks >>>> >>> >>> -- >>> You received this message because you are subscribed to the Google >>> Groups "elixir-lang-core" group. >>> To unsubscribe from this group and stop receiving emails from it, send >>> an email to elixir-l...@googlegroups.com. >>> To view this discussion on the web visit >>> https://groups.google.com/d/msgid/elixir-lang-core/57e4a930-f4f2-4efa-a0bf-35f470a652a6%40googlegroups.com >>> >>> <https://groups.google.com/d/msgid/elixir-lang-core/57e4a930-f4f2-4efa-a0bf-35f470a652a6%40googlegroups.com?utm_medium=email&utm_source=footer> >>> . >>> For more options, visit https://groups.google.com/d/optout. >>> >> >> -- >> You received this message because you are subscribed to a topic in the >> Google Groups "elixir-lang-core" group. >> To unsubscribe from this topic, visit >> https://groups.google.com/d/topic/elixir-lang-core/d9ZjViQaOY8/unsubscribe >> . >> To unsubscribe from this group and all its topics, send an email to >> elixir-l...@googlegroups.com. >> To view this discussion on the web visit >> https://groups.google.com/d/msgid/elixir-lang-core/CABu8xFBrM7LuJoZT0HzPQ-ifxOSgVZT03XwRu%3D-pC%3DQ%3D5Ow21Q%40mail.gmail.com >> >> <https://groups.google.com/d/msgid/elixir-lang-core/CABu8xFBrM7LuJoZT0HzPQ-ifxOSgVZT03XwRu%3D-pC%3DQ%3D5Ow21Q%40mail.gmail.com?utm_medium=email&utm_source=footer> >> . >> For more options, visit https://groups.google.com/d/optout. >> >> >> > -- > You received this message because you are subscribed to a topic in the > Google Groups "elixir-lang-core" group. > To unsubscribe from this topic, visit > https://groups.google.com/d/topic/elixir-lang-core/d9ZjViQaOY8/unsubscribe > . > To unsubscribe from this group and all its topics, send an email to > elixir-l...@googlegroups.com <javascript:>. > To view this discussion on the web visit > https://groups.google.com/d/msgid/elixir-lang-core/130d4573-9194-4d91-be5b-c2ed909f2001%40googlegroups.com > > <https://groups.google.com/d/msgid/elixir-lang-core/130d4573-9194-4d91-be5b-c2ed909f2001%40googlegroups.com?utm_medium=email&utm_source=footer> > . > For more options, visit https://groups.google.com/d/optout. > > > -- You received this message because you are subscribed to the Google Groups "elixir-lang-core" group. 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