Ash Framework•2mo ago

Managing Relationships - Cascading deletes for has_one relationships.

I'm trying to work through setting up relationships the Ash-way and here's roughly the structure I have: * A Campaign Has One Ship Has One Stash ** Has Many Crew Members I have set up my campaign resource like this:

def MyApp.Campaigns.Campaign do
  #...
  postgres do
    #...
    references do
      reference :stash, on_delete: :delete
      reference :ship, on_delete: :delete
    end
  end

  actions do
    create :create do
      #...
      change manage_relationship(:stash, type: :direct_control)
      change manage_relationship(:ship, type: :direct_control)
    end
    # ... other actions
    destroy :destroy do
      accept [:id]

      change cascade_destroy(:stash, action: :destroy)
      change cascade_destroy(:ship, action: :destroy)
    end
  end

  relationships do
    # ... other relationships
    has_one :stash, FiveApps.Campaigns.Stash
    has_one :ship, FiveApps.Campaigns.Ship
  end
end

def MyApp.Campaigns.Campaign do
  #...
  postgres do
    #...
    references do
      reference :stash, on_delete: :delete
      reference :ship, on_delete: :delete
    end
  end

  actions do
    create :create do
      #...
      change manage_relationship(:stash, type: :direct_control)
      change manage_relationship(:ship, type: :direct_control)
    end
    # ... other actions
    destroy :destroy do
      accept [:id]

      change cascade_destroy(:stash, action: :destroy)
      change cascade_destroy(:ship, action: :destroy)
    end
  end

  relationships do
    # ... other relationships
    has_one :stash, FiveApps.Campaigns.Stash
    has_one :ship, FiveApps.Campaigns.Ship
  end
end

3 Replies

AngryBadgerOP•2mo ago

I created a test to make sure I knew what I was doing (obvs I don't):

    # Wrote a test confirming that I can create a campaign with a stash (and a previous one that 
    # an empty ship is created if not provided... This passes.
    test "creates a campaign with a stash" do
      actor = generate(user())

      {:ok, campaign} =
        Campaigns.create_campaign(
          %{
            name: "Test Campaign",
            stash: %{notes: "test notes", credits: 1, patrons: 1, rivals: 1}
          },
          actor: actor,
          load: [:stash]
        )

      assert campaign.stash.id != nil
      assert campaign.stash.notes == "test notes"
      assert campaign.stash.credits == 1
      assert campaign.stash.patrons == 1
      assert campaign.stash.rivals == 1
    end

    # Then I wrote the delete test. Which fails.
    test "deletes the campaign" do
      campaign = generate(campaign())

      assert {:ok, _} = Campaigns.delete_campaign(campaign.id)
      assert Campaigns.get_campaign(campaign.id) == nil
    end

    # Wrote a test confirming that I can create a campaign with a stash (and a previous one that 
    # an empty ship is created if not provided... This passes.
    test "creates a campaign with a stash" do
      actor = generate(user())

      {:ok, campaign} =
        Campaigns.create_campaign(
          %{
            name: "Test Campaign",
            stash: %{notes: "test notes", credits: 1, patrons: 1, rivals: 1}
          },
          actor: actor,
          load: [:stash]
        )

      assert campaign.stash.id != nil
      assert campaign.stash.notes == "test notes"
      assert campaign.stash.credits == 1
      assert campaign.stash.patrons == 1
      assert campaign.stash.rivals == 1
    end

    # Then I wrote the delete test. Which fails.
    test "deletes the campaign" do
      campaign = generate(campaign())

      assert {:ok, _} = Campaigns.delete_campaign(campaign.id)
      assert Campaigns.get_campaign(campaign.id) == nil
    end

The error appears to be that when I delete the campaign it's not cascading the deletes to the has_one relationships. I followed the instructions on the documentation about deletion order and then on Ash.Resource.Change.CascadeDestroy but I am still getting this test failure:

     code:  assert {:ok, _} = Campaigns.delete_campaign(campaign.id)
     left:  {:ok, _}
     right: {
              :error,
              %Ash.Error.Invalid{errors: [%Ash.Error.Changes.InvalidAttribute{field: :id, message: "would leave records behind", private_vars: [constraint: "stashes_campaign_id_fkey", constraint_type: :foreign_key, detail: "Key (id)=(3b1fddf2-e317-49d1-9985-2f56c16f480b) is still referenced from table \"stashes\"."], value: nil, has_value?: false, splode: Ash.Error, bread_crumbs: [], vars: [], path: [], stacktrace: #Splode.Stacktrace<>, class: :invalid}]}
            }

     code:  assert {:ok, _} = Campaigns.delete_campaign(campaign.id)
     left:  {:ok, _}
     right: {
              :error,
              %Ash.Error.Invalid{errors: [%Ash.Error.Changes.InvalidAttribute{field: :id, message: "would leave records behind", private_vars: [constraint: "stashes_campaign_id_fkey", constraint_type: :foreign_key, detail: "Key (id)=(3b1fddf2-e317-49d1-9985-2f56c16f480b) is still referenced from table \"stashes\"."], value: nil, has_value?: false, splode: Ash.Error, bread_crumbs: [], vars: [], path: [], stacktrace: #Splode.Stacktrace<>, class: :invalid}]}
            }

I feel like I missed something super obvious in the documentation.

ZachDaniel•2mo ago

IIRC there are options to cascade_destroy that may help you there you may need the before_action option for example

AngryBadgerOP•2mo ago

Thanks @ZachDaniel , both suggestions resulted in the solution: add the option after_action?: false.

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Managing Relationships - Cascading deletes for has_one relationships.

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