allow users to configure to skip missing keys

Author: nduitz

lib/jsonapi/view.ex

@@ -248,6 +248,7 @@ defmodule JSONAPI.View do
     {path, opts} = Keyword.pop(opts, :path)
     {paginator, opts} = Keyword.pop(opts, :paginator)
     {polymorphic_resource?, _opts} = Keyword.pop(opts, :polymorphic_resource?, false)
+    {skip_missing_keys, _opts} = Keyword.pop(opts, :skip_missing_keys, false)
 
     quote do
       alias JSONAPI.{Serializer, View}
@@ -259,6 +260,7 @@ defmodule JSONAPI.View do
       @path unquote(path)
       @paginator unquote(paginator)
       @polymorphic_resource? unquote(polymorphic_resource?)
+      @skip_missing_keys unquote(skip_missing_keys)
 
       @impl View
       def id(nil), do: nil
@@ -278,11 +280,21 @@ defmodule JSONAPI.View do
               function_exported?(__MODULE__, :get_field, 3) ->
                 apply(__MODULE__, :get_field, [field, data, conn])
 
+              Map.has_key?(data, field) ->
+                Map.get(data, field)
+
+              @skip_missing_keys ->
+                :skip
+
               true ->
                 Map.get(data, field)
             end
 
-          Map.put(intermediate_map, field, value)
+          if value == :skip do
+            intermediate_map
+          else
+            Map.put(intermediate_map, field, value)
+          end
         end)
       end
 

test/jsonapi_test.exs

@@ -11,9 +11,9 @@ defmodule JSONAPITest do
   }
 
   defmodule PostView do
-    use JSONAPI.View
+    use JSONAPI.View, skip_missing_keys: true
 
-    def fields, do: [:text, :body, :excerpt, :first_character]
+    def fields, do: [:text, :body, :excerpt, :first_character, :maybe_missing_key]
     def type, do: "mytype"
 
     def relationships do
@@ -156,6 +156,40 @@ defmodule JSONAPITest do
     assert Map.has_key?(json, "links")
   end
 
+  test "does not include keys that are missing in data" do
+    conn =
+      :get
+      |> conn("/posts")
+      |> Plug.Conn.assign(:data, [@default_data])
+      |> Plug.Conn.assign(:meta, %{total_pages: 1})
+      |> Plug.Conn.fetch_query_params()
+      |> MyPostPlug.call([])
+
+    json = Jason.decode!(conn.resp_body)
+
+    data_list = Map.get(json, "data")
+    [data | _] = data_list
+    refute Map.has_key?(data["attributes"], "maybe_missing_key")
+  end
+
+  test "does include 'maybe_missing_key' if not configured" do
+    data = Map.put(@default_data, :maybe_missing_key, "foo")
+
+    conn =
+      :get
+      |> conn("/posts")
+      |> Plug.Conn.assign(:data, [data])
+      |> Plug.Conn.assign(:meta, %{total_pages: 1})
+      |> Plug.Conn.fetch_query_params()
+      |> MyPostPlug.call([])
+
+    json = Jason.decode!(conn.resp_body)
+
+    data_list = Map.get(json, "data")
+    [data | _] = data_list
+    assert Map.has_key?(data["attributes"], "maybe_missing_key")
+  end
+
   test "handles includes properly" do
     conn =
       :get