Ash Elixir•3y ago

Reading private attributes stopped working

I recently started not getting back private attributes in my update action. Record looks good via Resource.read, but attribute is nil. Perhaps due to a recent regression or change in semantics?

24 Replies

ZachDaniel•3y ago

🤔 interesting. So on an update the result doesn't contain private attributes, but when you read it back they are there? Are the attribute values nil on the way in?

\ ឵឵឵OP•3y ago

I've just noticed this, and the action I was working on is a manual, getting the attributes with Changeset.get_attribute. I'm on ash trunk and just updated. Not nil in Resource.read, looks good in Postgres.

ZachDaniel•3y ago

🤔 oh, so you're talking about before the update happens i.e

change fn changeset, _ -> 
  Ash.Changeset.get_attribute(changeset, :attr) #<- this is nil?
end

change fn changeset, _ -> 
  Ash.Changeset.get_attribute(changeset, :attr) #<- this is nil?
end

\ ឵឵឵OP•3y ago

Yep

ZachDaniel•3y ago

So generally speaking, that is caused by you passing in records to an update action that don't have all of the attributes selected I'd like to add an elegant "reselection" process to update actions that allow you to express the data that you need and have it be reselected before the action but until then, you'll have to make sure you've selected everything on a record before providing it for an update, or do the reselection yourself TO confirm that its nil because it hasn't been selected:

change fn changeset, _ -> 
  Ash.Resource.selected?(changeset.data, :attr) #<- will tell you if the attr was selected
  Ash.Changeset.get_attribute(changeset, :attr) 
end

change fn changeset, _ -> 
  Ash.Resource.selected?(changeset.data, :attr) #<- will tell you if the attr was selected
  Ash.Changeset.get_attribute(changeset, :attr) 
end

\ ឵឵឵OP•3y ago

Ok, right on. Something along the lines of:

actions do
  update do
    reselecting :attr
    # ...
  end
end

actions do
  update do
    reselecting :attr
    # ...
  end
end

ZachDaniel•3y ago

You could write a generic tool for this:

defmodule Reselect do
  use Ash.Resource.Change
  
  def change(changeset, opts, _) do
    changeset
    |> Ash.Changeset.before_action(fn changeset -> 
      if Enum.all?(opts[:attrs], &Ash.Resource.selected?(changeset.data, &1)) do
        changeset
      else
        %{changeset | data: changeset.api.reload!(changeset.data)}
      end
    end)
  end
end

change {Reselect, attrs: [:foo, :bar, :baz]}

defmodule Reselect do
  use Ash.Resource.Change
  
  def change(changeset, opts, _) do
    changeset
    |> Ash.Changeset.before_action(fn changeset -> 
      if Enum.all?(opts[:attrs], &Ash.Resource.selected?(changeset.data, &1)) do
        changeset
      else
        %{changeset | data: changeset.api.reload!(changeset.data)}
      end
    end)
  end
end

change {Reselect, attrs: [:foo, :bar, :baz]}

\ ឵឵឵OP•3y ago

Great! Thanks a bunch. Hmm, it doesn't seem to be working for the action in question. (still getting nil)

ZachDaniel•3y ago

Can you confirm if this: Ash.Resource.selected?(changeset.data, :attr) #<- will tell you if the attr was selected is returning true/false where you expect it to? or show me where you are doing get_attribute for example

\ ឵឵឵OP•3y ago

Ash.Resource.selected?(cs.data, :attr) == true Weirdly

ZachDaniel•3y ago

And what does changeset.attributes have in it? Does it contain %{attr: nil}?

\ ឵឵឵OP•3y ago

Nope, it is %{}

ZachDaniel•3y ago

:thinkies: what is cs.data.attr

\ ឵឵឵OP•3y ago

It is KeyError 😁

ZachDaniel•3y ago

what? is :attr not an attribute of your resource? To be clear, when I say :attr I mean whatever attribute you're checking with

\ ឵឵឵OP•3y ago

In that case, it is nil.

ZachDaniel•3y ago

So the passed in record has a nil value for the attribute, and it was selected, meaning that it should be nil Why should it not be nil?

\ ឵឵឵OP•3y ago

Righto, the passed in record does have it as nil, I was thinking we were trying to indicate that it should be reselected. (the DB record is not nil)

ZachDaniel•3y ago

gotcha. Well you could remove that if Enum.all check on your reselect change or add an option in there to force reselect some of them

\ ឵឵឵OP•3y ago

Right on, then it would simply indicate to reload the entire record, which is just fine 🙂

ZachDaniel•3y ago

You could also use changeset context for that

if changeset.context[:reload?] do

if changeset.context[:reload?] do

and then

Ash.Changeset.set_context(changeset, %{reload?: true})

Ash.Changeset.set_context(changeset, %{reload?: true})

where you call the action if you want to make it opt-in

\ ឵឵឵OP•3y ago

I think it's probably acceptable to have it, but it seems more idiomatic to ensure that the callers are threading it through rather than pushing this into the actions themselves. Actually, a change to do a reload if the indicated attributes are nil would probably be a fine middleground.

defmodule Reselecting do
  use Ash.Resource.Change

  def change(changeset, opts, _) do
    changeset
    |> Ash.Changeset.before_action(fn changeset ->
      if Enum.all?(opts[:attrs], &(changeset.data.[&1] != nil)) do
        changeset
      else
        %{changeset | data: changeset.api.reload!(changeset.data)}
      end
    end)
  end
end

defmodule Reselecting do
  use Ash.Resource.Change

  def change(changeset, opts, _) do
    changeset
    |> Ash.Changeset.before_action(fn changeset ->
      if Enum.all?(opts[:attrs], &(changeset.data.[&1] != nil)) do
        changeset
      else
        %{changeset | data: changeset.api.reload!(changeset.data)}
      end
    end)
  end
end

ZachDaniel•3y ago

I think you'll want Map.get there but yeah

\ ឵឵឵OP•3y ago

Yep, works great, thanks very much mate! 🙂

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