Fix custom type spec

lib/typespec.ex

@@ -138,30 +138,30 @@ defmodule Strukt.Typespec do
   defp type_to_type_name(:date),
     do: compose_call(Date, :t, [])
 
-  defp type_to_type_name({:__aliases__, _, parts} = ast) do
-    case Module.concat(parts) do
+  defp type_to_type_name(mod) when is_atom(mod) and not is_nil(mod) do
+    case mod do
       Ecto.Enum ->
         primitive(:atom)
 
       Ecto.UUID ->
-        primitive(:string)
+        compose_call(Ecto.UUID, :t, [])
 
       mod ->
-        with {:module, _} <- Code.ensure_compiled(mod) do
-          try do
-            if Kernel.Typespec.defines_type?(mod, {:t, 0}) do
-              compose_call(ast, :t, [])
-            else
-              # No t/0 type defined, so fallback to any/0
-              primitive(:any)
-            end
-          rescue
-            ArgumentError ->
-              # We shouldn't hit this branch, but if Elixir can't find module metadata
-              # during defines_type?, it raises ArgumentError, so we handle this like the
-              # other pessimistic cases
-              primitive(:any)
-          end
+        with {:module, _} <- Code.ensure_compiled(mod),
+             {:ok, mod_types} <- Code.Typespec.fetch_types(mod),
+             t0 when not is_nil(t0) <-
+               Enum.find(
+                 mod_types,
+                 &match?(
+                   {kind, {:t, _, args}} when kind in [:type, :opaque] and length(args) == 0,
+                   &1
+                 )
+               ) do
+          compose_call(
+            {:__aliases__, [alias: false], Enum.map(Module.split(mod), &String.to_atom/1)},
+            :t,
+            []
+          )
         else
           _ ->
             # Module is unable to be loaded, either due to compiler deadlock, or because

test/strukt_test.exs

@@ -545,6 +545,26 @@ defmodule Strukt.Test do
              Fixtures.EmbedsOneTypeSpec.expected_type_spec_ast_str()
   end
 
+  test "custom ecto type" do
+    require Fixtures.CustomEctoTypeTypeSepc
+
+    assert inspect(
+             Strukt.Typespec.generate(%Strukt.Typespec{
+               caller: Strukt.Test.Fixtures.CustomEctoTypeTypeSepc,
+               fields: [:uri],
+               info: %{
+                 uri: %{
+                   type: :field,
+                   value_type: Custom.EctoType,
+                   required: true
+                 }
+               },
+               embeds: []
+             })
+           ) ==
+             Fixtures.CustomEctoTypeTypeSepc.expected_type_spec_ast_str()
+  end
+
   defp changeset_errors(%Ecto.Changeset{} = cs) do
     cs
     |> Ecto.Changeset.traverse_errors(fn {msg, opts} ->

test/support/defstruct_fixtures.ex

@@ -9,6 +9,31 @@ defmodule Aux do
   end
 end
 
+defmodule Custom.EctoType do
+  @moduledoc "Custom Ecto Type for test"
+  @type t() :: URI.t()
+
+  use Ecto.Type
+  def type, do: :map
+
+  def cast(uri) when is_binary(uri), do: {:ok, URI.parse(uri)}
+  def cast(%URI{} = uri), do: {:ok, uri}
+
+  def cast(_), do: :error
+
+  def load(data) when is_map(data) do
+    data =
+      for {key, val} <- data do
+        {String.to_existing_atom(key), val}
+      end
+
+    {:ok, struct!(URI, data)}
+  end
+
+  def dump(%URI{} = uri), do: {:ok, Map.from_struct(uri)}
+  def dump(_), do: :error
+end
+
 defmodule Strukt.Test.Fixtures do
   use Strukt
 
@@ -72,6 +97,25 @@ defmodule Strukt.Test.Fixtures do
     end
   end
 
+  defmodule CustomEctoTypeTypeSepc do
+    use Strukt
+
+    @primary_key false
+    defstruct do
+      field(:uri, Custom.EctoType)
+      field(:foobar, :string)
+    end
+
+    defmacro expected_type_spec_ast_str do
+      quote context: __MODULE__ do
+        @type t :: %__MODULE__{
+                uri: Custom.EctoType.t()
+              }
+      end
+      |> inspect()
+    end
+  end
+
   defmodule CustomFields do
     @moduledoc "This module represents the params keys are not snake case"
 
@@ -327,7 +371,9 @@ defmodule Strukt.Test.Fixtures do
   defstruct ValidateSets do
     @moduledoc "This module exercises validations based on set membership"
 
-    field(:one_of, :string, one_of: [values: ["a", "b", "c"], message: "must be one of [a, b, c]"])
+    field(:one_of, :string,
+      one_of: [values: ["a", "b", "c"], message: "must be one of [a, b, c]"]
+    )
 
     field(:none_of, :string,
       none_of: [values: ["a", "b", "c"], message: "cannot be one of [a, b, c]"]