lazy-load api version upon first call rather than instantiation

pynautobot/core/api.py

@@ -13,7 +13,7 @@
 # limitations under the License.
 #
 # This file has been modified by NetworktoCode, LLC.
-
+from functools import cached_property
 from packaging import version
 import requests
 from requests.adapters import HTTPAdapter
@@ -110,15 +110,13 @@ def __init__(
         self.users = App(self, "users")
         self.plugins = PluginsApp(self)
         self.graphql = GraphQLQuery(self)
-        self._validate_version()
 
-    def _validate_version(self):
+    def _validate_version(self, api_version: str) -> None:
         """Validate API version if eq or ge than 2.0 raise an error."""
-        api_version = self.version
         if api_version.replace(".", "").isnumeric() and version.parse(api_version) < version.parse("2.0"):
             raise ValueError("Nautobot version 1 detected, please downgrade pynautobot to version 1.x")
 
-    @property
+    @cached_property
     def version(self):
         """Retrieves the version of the Nautobot REST API that the connected instance is using.
 
@@ -142,12 +140,15 @@ def version(self):
             '1.0'
         """
 
-        return Request(
+        v = Request(
             base=self.base_url,
             http_session=self.http_session,
             api_version=self.api_version,
             token=self.token,
         ).get_version()
+        self._validate_version(v)
+
+        return v
 
     def openapi(self):
         """Retrieves the OpenAPI specification (OAS) document for the connected Nautobot instance.

tests/test_api.py

@@ -69,7 +69,7 @@ class ResponseHeadersWithVersion:
     )
     def test_api_version(self, *_):
         with self.assertRaises(ValueError) as error:
-            pynautobot.api(host)
+            pynautobot.api(host).version
         self.assertEqual(
             str(error.exception), "Nautobot version 1 detected, please downgrade pynautobot to version 1.x"
         )
@@ -124,6 +124,31 @@ def test_api_status(self, *_):
         self.assertEqual(api.status()["nautobot-version"], "1.3.2")
 
 
+class ApiLazyLoadVersionTestCase(unittest.TestCase):
+    """
+    Tests that version is lazy loaded on the first API call, rather than on instantiation
+    """
+
+    @patch("urllib3.connectionpool.HTTPConnectionPool._get_conn")
+    def test_lazy_load_version(self, getconn_mock):
+        getconn_mock.return_value.getresponse.side_effect = [
+            Mock(status=200, msg=HTTPMessage()),
+        ]
+
+        api = pynautobot.api(
+            "http://any.url/",
+            retries=2,
+        )
+
+        assert getconn_mock.return_value.request.mock_calls == []
+
+        api.version
+
+        assert getconn_mock.return_value.request.mock_calls == [
+            call("GET", "/api/", body=None, headers=ANY),
+        ]
+
+
 class ApiRetryTestCase(unittest.TestCase):
     class ResponseWithStatus:
         ok = False
@@ -137,12 +162,10 @@ def test_api_retry(self, getconn_mock):
             Mock(status=200, msg=HTTPMessage()),
         ]
 
-        api = pynautobot.api(
+        pynautobot.api(
             "http://any.url/",
             retries=2,
-        )
-        with patch("pynautobot.api.version", "2.0"):
-            api.version
+        ).version
 
         assert getconn_mock.return_value.request.mock_calls == [
             call("GET", "/api/", body=None, headers=ANY),