From 415b90caaf95da0f420f39db6071e04d22887ddf Mon Sep 17 00:00:00 2001
From: Pete West <peterjwest3@gmail.com>
Date: Tue, 14 Jul 2020 16:19:45 +0100
Subject: [PATCH] Add support for recursive models and unit test

---
 flask_restx/swagger.py |  2 ++
 tests/test_swagger.py  | 21 +++++++++++++++++++++
 2 files changed, 23 insertions(+)

diff --git a/flask_restx/swagger.py b/flask_restx/swagger.py
index 616e5a67..8d0f065c 100644
--- a/flask_restx/swagger.py
+++ b/flask_restx/swagger.py
@@ -657,6 +657,8 @@ def register_model(self, model):
         if name not in self.api.models:
             raise ValueError("Model {0} not registered".format(name))
         specs = self.api.models[name]
+        if name in self._registered_models:
+            return ref(model)
         self._registered_models[name] = specs
         if isinstance(specs, ModelBase):
             for parent in specs.__parents__:
diff --git a/tests/test_swagger.py b/tests/test_swagger.py
index be3c934f..f52748a9 100644
--- a/tests/test_swagger.py
+++ b/tests/test_swagger.py
@@ -2057,6 +2057,27 @@ def get(self):
 
         client.get_specs(status=500)
 
+    def test_recursive_model(self, api, client):
+        fields = api.model('Person', {
+            'name': restx.fields.String,
+            'age': restx.fields.Integer,
+            'birthdate': restx.fields.DateTime,
+        })
+
+        fields["children"] = restx.fields.List(
+            restx.fields.Nested(fields),
+            default=[],
+        )
+
+        @api.route('/recursive-model/')
+        @api.doc(get={'model': fields})
+        class ModelAsDict(restx.Resource):
+            @api.marshal_with(fields)
+            def get(self):
+                return {}
+
+        client.get_specs(status=200)
+
     def test_specs_no_duplicate_response_keys(self, api, client):
         """
         This tests that the swagger.json document will not be written with duplicate object keys