Process nested schema reference

lib/open_api/processor/type.ex

@@ -90,8 +90,15 @@ defmodule OpenAPI.Processor.Type do
   # Schema references
   #
   def from_schema(state, {:ref, full_path}) do
-    schema_spec = Map.fetch!(state.schema_specs_by_path, full_path)
-    from_schema(state, schema_spec)
+    with {_absolute_file, ["components", "schemas", schema_name]} <- full_path,
+         %State{spec: %Spec{components: %Spec.Components{schemas: schemas}}} = state,
+         {:ref, _} = schema_ref <- Map.get(schemas, schema_name) do
+      from_schema(state, schema_ref)
+    else
+      _ ->
+        schema_spec = Map.fetch!(state.schema_specs_by_path, full_path)
+        from_schema(state, schema_spec)
+    end
   end
 
   # Primitives

test/fixture/schema-reference.yaml

@@ -0,0 +1,29 @@
+openapi: "3.1.0"
+info:
+  title: Schema Reference Spec
+  version: 1
+paths:
+  "/example_reference":
+    get:
+      description: "Example reference endpoint"
+      operationId: example_reference
+      summary: "Example reference endpoint"
+      responses:
+        "200":
+          description: "Success"
+          content:
+            "application/json":
+              schema:
+                "$ref": "#/components/schemas/user_reference"
+components:
+  schemas:
+    user:
+      type: object
+      properties:
+        id:
+          type: integer
+      required:
+        - id
+        - team
+    user_reference:
+      "$ref": "#/components/schemas/user"