improvement: helpful error message when mixing entity inline/block syntax

Author: joshprice

lib/spark/dsl/extension.ex

@@ -1252,6 +1252,25 @@ defmodule Spark.Dsl.Extension do
           end
 
           @moduledoc false
+
+          # Generate mixed syntax macro only for entities without optional args
+          if not Enum.any?(entity.args, fn
+               {:optional, _, _} -> true
+               {:optional, _} -> true
+               _ -> false
+             end) do
+            defmacro unquote(entity.name)(unquote_splicing(args), extra_opts, [do: _] = _block) do
+              entity_name = unquote(entity.name)
+
+              raise Spark.Error.DslError,
+                module: __CALLER__.module,
+                message:
+                  "Cannot use both inline syntax and block syntax for entity `#{entity_name}`. " <>
+                    "Use block syntax `#{entity_name} args... do ... end`",
+                path: unquote(section_path ++ nested_entity_path)
+            end
+          end
+
           defmacro unquote(entity.name)(unquote_splicing(args), opts \\ nil) do
             section_path = unquote(Macro.escape(section_path))
             entity_schema = unquote(Macro.escape(entity.schema))

test/dsl_test.exs

@@ -396,7 +396,7 @@ defmodule Spark.DslTest do
     end
   end
 
-  describe "DSL section syntax validation" do
+  describe "DSL section and entity syntax validation" do
     test "mixed inline/block syntax should provide helpful error" do
       assert_raise Spark.Error.DslError,
                    ~r/Cannot use both inline syntax and block syntax.*personal_details/,
@@ -424,6 +424,23 @@ defmodule Spark.DslTest do
                      end
                    end
     end
+
+    test "mixed inline/block syntax for entity should provide helpful error" do
+      assert_raise Spark.Error.DslError,
+                   ~r/Cannot use both inline syntax and block syntax.*preset/,
+                   fn ->
+                     defmodule EntityMixedSyntax do
+                       @moduledoc false
+                       use Spark.Test.Contact
+
+                       presets do
+                         preset :einstein, default_message: "E=mc²" do
+                           contacter(fn x -> x end)
+                         end
+                       end
+                     end
+                   end
+    end
   end
 
   describe "optional entity arguments" do