> We need to document that once an attribute has been registered to accumulate or persist, it can't be done undone unless the attribute is deleted.
How is it undone today? Allen Madsen http://www.allenmadsen.com On Tue, Jul 2, 2019 at 1:24 AM José Valim <[email protected]> wrote: > Thanks for the proposal. > > I like has_attribute?. I prefer it over attribute_registered? because what > would happen if you set an attribute without registered it? Should it > return false for attribute_registetered? So has_attribute? is less > ambiguous, although I would only support has_attribute?/2 for now. > > Notice in order to implement this, you will have to change > register_attribute to store something when called without the :persist or > :accumulate. But it should be a matter of adding an else here: > https://github.com/elixir-lang/elixir/blob/master/lib/elixir/lib/module.ex#L1308-L1311 > > Something like: > > else > :ets.insert_new(set, {attribute, nil, nil}) > end > > We need to document that once an attribute has been registered to > accumulate or persist, it can't be done undone unless the attribute is > deleted. > > *José Valim* > www.plataformatec.com.br > Skype: jv.ptec > Founder and Director of R&D > > > On Tue, Jul 2, 2019 at 5:42 AM Allen Madsen <[email protected]> wrote: > >> In working with the ExUnit code, there are at least two places where I >> think being able to introspect on module attributes would be useful. >> >> One is here >> <https://github.com/elixir-lang/elixir/blob/master/lib/ex_unit/lib/ex_unit/case.ex#L227-L233>. >> In this code it would be useful to know if a module attribute has been set >> already. This code checks to see if it has a value. However, if a user set >> the value to `nil`, this code wouldn't be able to tell. >> >> Another situation it would be useful, is in this PR: >> https://github.com/elixir-lang/elixir/pull/9181. Specifically, this check >> <https://github.com/elixir-lang/elixir/blob/e24a18338ef908aba8bf83e315d6e3938dbefce7/lib/ex_unit/lib/ex_unit/case.ex#L427-L431>, >> where it would also be useful to know if the attribute is registered with >> accumulate or not. >> >> So, the proposal is an API something like this: >> >> defmodule X do >> Module.register_attribute(__MODULE__, :foo, accumulate: true) >> @bar true >> >> Module.attribute_registered?(__MODULE__, :foo) #=> true >> Module.attribute_registered?(__MODULE__, :foo, accumulate: true) #=> >> true >> Module.attribute_registered?(__MODULE__, :foo, persist: true) #=> false >> >> Module.attribute_registered?(__MODULE__, :bar) #=> true >> Module.attribute_registered?(__MODULE__, :bar, accumulate: true) #=> >> false >> >> Module.attribute_registered?(__MODULE__, :baz) #=> false >> end >> >> The third argument would be a subset match of the options. >> >> Thoughts? >> >> -- >> 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 [email protected]. >> To view this discussion on the web visit >> https://groups.google.com/d/msgid/elixir-lang-core/39c87e02-8ed2-49ed-9754-d0e8f0bafd7e%40googlegroups.com >> <https://groups.google.com/d/msgid/elixir-lang-core/39c87e02-8ed2-49ed-9754-d0e8f0bafd7e%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. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To view this discussion on the web visit > https://groups.google.com/d/msgid/elixir-lang-core/CAGnRm4%2Bb4afMwPpQP6Jv%3D_bCWJvRskNd%3DJJA_OHArJMH7621kg%40mail.gmail.com > <https://groups.google.com/d/msgid/elixir-lang-core/CAGnRm4%2Bb4afMwPpQP6Jv%3D_bCWJvRskNd%3DJJA_OHArJMH7621kg%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 the Google Groups "elixir-lang-core" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/elixir-lang-core/CAK-y3CvpoHqHuGk0CGq%3DBvam4zab-B1bcTS1KBOOdNPvkHHhXw%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
