Fix string serialization error raising (#1062)

* fix string serialization

* rescue Protocol.UndefinedError

* test name tweak

Co-authored-by: Vince Foley <[email protected]>

Author: emeryotopalik

lib/absinthe/phase/document/result.ex

@@ -54,15 +54,18 @@ defmodule Absinthe.Phase.Document.Result do
           try do
             Type.Scalar.serialize(schema_node, value)
           rescue
-            Absinthe.SerializationError ->
-              raise(Absinthe.SerializationError, """
-              Could not serialize term #{inspect(value)} as type #{schema_node.name}
-
-              When serializing the field:
-              #{emitter.parent_type.name}.#{emitter.schema_node.name} (#{
-                emitter.schema_node.__reference__.location.file
-              }:#{emitter.schema_node.__reference__.location.line})
-              """)
+            _e in [Absinthe.SerializationError, Protocol.UndefinedError] ->
+              raise(
+                Absinthe.SerializationError,
+                """
+                Could not serialize term #{inspect(value)} as type #{schema_node.name}
+
+                When serializing the field:
+                #{emitter.parent_type.name}.#{emitter.schema_node.name} (#{
+                  emitter.schema_node.__reference__.location.file
+                }:#{emitter.schema_node.__reference__.location.line})
+                """
+              )
           end
 
         %Type.Enum{} = schema_node ->

test/absinthe/integration/execution/serialization_test.exs

@@ -16,6 +16,10 @@ defmodule Absinthe.Integration.Execution.SerializationTest do
       field :bad_boolean, :boolean do
         resolve fn _, _, _ -> {:ok, "true"} end
       end
+
+      field :bad_string, :string do
+        resolve fn _, _, _ -> {:ok, %{}} end
+      end
     end
   end
 
@@ -45,4 +49,13 @@ defmodule Absinthe.Integration.Execution.SerializationTest do
       Absinthe.run(@query, Schema)
     end)
   end
+
+  @query """
+  query { badString }
+  """
+  test "returning a type that can't `to_string` for a string raises" do
+    assert_raise(Absinthe.SerializationError, fn ->
+      Absinthe.run(@query, Schema)
+    end)
+  end
 end