Fix client instances sharing same kwarg values (#50)

src/declarativex/models.py

@@ -228,16 +228,16 @@ def merge(self, other: "ClientConfiguration") -> "ClientConfiguration":
         take precedence over the values of this configuration.
         """
         return ClientConfiguration(
-            base_url=self.base_url if self.base_url else other.base_url,
-            auth=self.auth if self.auth else other.auth,
+            base_url=other.base_url if other.base_url else self.base_url,
+            auth=other.auth if other.auth else self.auth,
             default_query_params={
-                **other.default_query_params,
                 **self.default_query_params,
+                **other.default_query_params,
             },
-            default_headers={**other.default_headers, **self.default_headers},
-            middlewares=[*other.middlewares, *self.middlewares],
+            default_headers={**self.default_headers, **other.default_headers},
+            middlewares=other.middlewares,
             error_mappings={**other.error_mappings, **self.error_mappings},
-            proxies=merge_proxies(other.proxies, self.proxies),
+            proxies=merge_proxies(self.proxies, other.proxies),
         )
 
     @classmethod

tests/test_sync_clients.py

@@ -356,3 +356,36 @@ def get_users(files: Annotated[dict, Files]) -> dict:
         in send_mock.send.call_args_list[0].args[0].headers["content-type"]
     )
     assert file_content in send_mock.send.call_args_list[0].args[0].read()
+
+
+def test_multiple_instances():
+    PMAN_URL = "https://postman-echo.com"
+    INVALID_URL = "https://invalid.com"
+
+    class EchoClient(BaseClient):
+        @http("get", "/get")
+        def sample_get(self) -> dict:
+            ...
+
+    auth1 = httpx.BasicAuth("client1", "secret1")
+    client1 = EchoClient(
+        base_url=PMAN_URL,
+        default_headers={"x-request-origin": "client1"},
+        default_query_params={"x-my-param": "client1-param"},
+        auth=auth1,
+    )
+
+    result1 = client1.sample_get()
+    assert result1["headers"]["x-request-origin"] == "client1"
+    assert result1["args"]["x-my-param"] == "client1-param"
+
+    auth2 = httpx.BasicAuth("client2", "secret2")
+    client2 = EchoClient(
+        base_url=INVALID_URL,
+        default_headers={"x-request-origin": "client2"},
+        default_query_params={"x-my-param": "client2-param"},
+        auth=auth2,
+    )
+
+    with pytest.raises(httpx.RequestError):
+        client2.sample_get()