fix: handle Union types in serialization

Author: zachdaniel

lib/ash_json_api/serializer.ex

@@ -1211,10 +1211,40 @@ defmodule AshJsonApi.Serializer do
     Decimal.to_string(value)
   end
 
+  def serialize_value(
+        %Ash.Union{type: name, value: inner_value},
+        Ash.Type.Union,
+        constraints,
+        domain,
+        opts
+      ) do
+    case constraints[:types][name] do
+      nil ->
+        inner_value
+
+      config ->
+        serialize_value(
+          inner_value,
+          Ash.Type.get_type(config[:type]),
+          config[:constraints] || [],
+          domain,
+          opts
+        )
+    end
+  end
+
   def serialize_value(value, type, constraints, domain, opts) do
     {type, constraints} = flatten_new_type(type, constraints || [])
     opts = [skip_only_primary_key?: false, top_level?: false] |> Keyword.merge(opts)
 
+    if type == Ash.Type.Union and match?(%Ash.Union{}, value) do
+      serialize_value(value, Ash.Type.Union, constraints, domain, opts)
+    else
+      do_serialize_value(value, type, constraints, domain, opts)
+    end
+  end
+
+  defp do_serialize_value(value, type, constraints, domain, opts) do
     with Ash.Type.Struct <- type,
          instance_of when not is_nil(instance_of) <- constraints[:instance_of],
          true <- Ash.Resource.Info.resource?(instance_of) do

test/acceptance/union_test.exs

@@ -0,0 +1,165 @@
+# SPDX-FileCopyrightText: 2019 ash_json_api contributors <https://github.com/ash-project/ash_json_api/graphs/contributors>
+#
+# SPDX-License-Identifier: MIT
+
+defmodule Test.Acceptance.UnionTest do
+  use ExUnit.Case, async: true
+
+  defmodule HeartRate do
+    use Ash.Resource,
+      domain: nil,
+      data_layer: :embedded
+
+    attributes do
+      attribute(:bpm, :integer, public?: true, allow_nil?: false)
+    end
+
+    actions do
+      defaults([:read, :destroy, create: :*, update: :*])
+    end
+  end
+
+  defmodule BloodPressure do
+    use Ash.Resource,
+      domain: nil,
+      data_layer: :embedded
+
+    attributes do
+      attribute(:systolic, :integer, public?: true, allow_nil?: false)
+      attribute(:diastolic, :integer, public?: true, allow_nil?: false)
+    end
+
+    actions do
+      defaults([:read, :destroy, create: :*, update: :*])
+    end
+  end
+
+  defmodule MeasurementValue do
+    use Ash.Type.NewType,
+      subtype_of: :union,
+      constraints: [
+        types: [
+          heart_rate: [
+            type: HeartRate,
+            tag: :type,
+            tag_value: "heart_rate"
+          ],
+          blood_pressure: [
+            type: BloodPressure,
+            tag: :type,
+            tag_value: "blood_pressure"
+          ],
+          note: [
+            type: :string
+          ]
+        ]
+      ]
+  end
+
+  defmodule Measurement do
+    use Ash.Resource,
+      domain: Test.Acceptance.UnionTest.Domain,
+      data_layer: Ash.DataLayer.Ets,
+      extensions: [AshJsonApi.Resource]
+
+    ets do
+      private?(true)
+    end
+
+    json_api do
+      type "measurement"
+
+      routes do
+        base "/measurements"
+        get :read
+        index :read
+      end
+    end
+
+    attributes do
+      uuid_primary_key(:id)
+      attribute(:value, MeasurementValue, public?: true, allow_nil?: false)
+      attribute(:values, {:array, MeasurementValue}, public?: true, default: [])
+    end
+
+    actions do
+      default_accept([:value, :values])
+      defaults([:read, :destroy, create: :*, update: :*])
+    end
+  end
+
+  defmodule Domain do
+    use Ash.Domain,
+      otp_app: :ash_json_api,
+      extensions: [AshJsonApi.Domain]
+
+    json_api do
+      authorize? false
+      log_errors? false
+    end
+
+    resources do
+      resource Measurement
+    end
+  end
+
+  defmodule Router do
+    use AshJsonApi.Router, domain: Domain
+  end
+
+  import AshJsonApi.Test
+
+  setup do
+    Application.put_env(:ash_json_api, Domain, json_api: [test_router: Router])
+    :ok
+  end
+
+  test "renders an embedded resource inside a union without needing Jason.Encoder" do
+    m =
+      Measurement
+      |> Ash.Changeset.for_create(:create, %{
+        value: %{type: "heart_rate", bpm: 72}
+      })
+      |> Ash.create!()
+
+    response = Domain |> get("/measurements/#{m.id}", status: 200)
+    attrs = response.resp_body["data"]["attributes"]
+
+    assert attrs["value"] == %{"bpm" => 72}
+  end
+
+  test "renders a primitive value inside a union" do
+    m =
+      Measurement
+      |> Ash.Changeset.for_create(:create, %{
+        value: "feeling fine"
+      })
+      |> Ash.create!()
+
+    response = Domain |> get("/measurements/#{m.id}", status: 200)
+    attrs = response.resp_body["data"]["attributes"]
+
+    assert attrs["value"] == "feeling fine"
+  end
+
+  test "renders an array of unions" do
+    m =
+      Measurement
+      |> Ash.Changeset.for_create(:create, %{
+        value: %{type: "heart_rate", bpm: 60},
+        values: [
+          %{type: "heart_rate", bpm: 80},
+          %{type: "blood_pressure", systolic: 120, diastolic: 80}
+        ]
+      })
+      |> Ash.create!()
+
+    response = Domain |> get("/measurements/#{m.id}", status: 200)
+    attrs = response.resp_body["data"]["attributes"]
+
+    assert attrs["values"] == [
+             %{"bpm" => 80},
+             %{"systolic" => 120, "diastolic" => 80}
+           ]
+  end
+end

test/spec_compliance/fetching_data/pagination/keyset_test.exs

@@ -552,7 +552,7 @@ defmodule AshJsonApiTest.FetchingData.Pagination.Keyset do
 
       assert %{"meta" => meta} = conn.resp_body
 
-      assert meta == %{"page" => %{"total" => 15, "limit" => 5, "more?" => true}}
+      assert meta == %{"page" => %{"total" => 15, "limit" => 5}}
     end
 
     test "collection total is not present when count is false" do