fix: preserve omitted and null JSON request bodies

An optional nullable primitive request body rendered an orphan `else:` in
the generated endpoint, so the client did not compile. The JSON body macro
now uses the normal property transform, drops the `json` kwarg when the
serialised value is UNSET, and sends explicit None as raw `content=b"null"`
because HTTPX treats `json=None` as no body. Signature requiredness, nested
serialisation and declared Content-Type are unchanged.

Add generated-client regressions for OpenAPI 3.0 and 3.1 nullable bodies
that assert request bytes through HTTPX for omitted, UNSET, None and
concrete values, and regenerate the affected endpoint golden records.

Fixes #1425

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

Author: CodingCossack

end_to_end_tests/functional_tests/generated_code_execution/test_nullable_request_bodies.py

@@ -21,6 +21,10 @@ def _get_kwargs(
     }
 
     _kwargs["json"] = body.to_dict()
+    if _kwargs["json"] is None:
+        # HTTPX treats json=None as no body; send JSON null explicitly.
+        _kwargs["content"] = b"null"
+        del _kwargs["json"]
 
     headers["Content-Type"] = "application/json"
 

end_to_end_tests/golden-records/escapes-client/escapes_client/api/default/misc_metadata_escapes.py

@@ -21,6 +21,10 @@ def _get_kwargs(
     }
 
     _kwargs["json"] = body.to_dict()
+    if _kwargs["json"] is None:
+        # HTTPX treats json=None as no body; send JSON null explicitly.
+        _kwargs["content"] = b"null"
+        del _kwargs["json"]
 
     headers["Content-Type"] = "application/json"
 

end_to_end_tests/golden-records/escapes-client/escapes_client/api/default/non_string_example.py

@@ -21,6 +21,10 @@ def _get_kwargs(
     }
 
     _kwargs["json"] = body.to_dict()
+    if _kwargs["json"] is None:
+        # HTTPX treats json=None as no body; send JSON null explicitly.
+        _kwargs["content"] = b"null"
+        del _kwargs["json"]
 
     headers["Content-Type"] = "application/json"
 

end_to_end_tests/golden-records/escapes-client/escapes_client/api/default/property_escapes.py

@@ -33,6 +33,10 @@ def _get_kwargs(
     }
 
     _kwargs["json"] = body.to_dict()
+    if _kwargs["json"] is None:
+        # HTTPX treats json=None as no body; send JSON null explicitly.
+        _kwargs["content"] = b"null"
+        del _kwargs["json"]
 
     headers["Content-Type"] = 'application/json; profile="https://example.com/escape" + print("uh oh") + "'
 

end_to_end_tests/golden-records/escapes-client/escapes_client/api/printtag_escape/with_braces_path.py

@@ -20,8 +20,15 @@ def _get_kwargs(
         "url": "/bodies/json-like",
     }
 
+    _kwargs["json"] = UNSET
     if not isinstance(body, Unset):
         _kwargs["json"] = body.to_dict()
+    if isinstance(_kwargs["json"], Unset):
+        del _kwargs["json"]
+    elif _kwargs["json"] is None:
+        # HTTPX treats json=None as no body; send JSON null explicitly.
+        _kwargs["content"] = b"null"
+        del _kwargs["json"]
 
     headers["Content-Type"] = "application/vnd+json"
 

end_to_end_tests/golden-records/my-test-api-client/my_test_api_client/api/bodies/json_like.py

@@ -20,8 +20,15 @@ def _get_kwargs(
         "url": "/bodies/optional",
     }
 
+    _kwargs["json"] = UNSET
     if not isinstance(body, Unset):
         _kwargs["json"] = body.to_dict()
+    if isinstance(_kwargs["json"], Unset):
+        del _kwargs["json"]
+    elif _kwargs["json"] is None:
+        # HTTPX treats json=None as no body; send JSON null explicitly.
+        _kwargs["content"] = b"null"
+        del _kwargs["json"]
 
     headers["Content-Type"] = "application/json"
 

end_to_end_tests/golden-records/my-test-api-client/my_test_api_client/api/bodies/optional_body.py

@@ -23,8 +23,15 @@ def _get_kwargs(
     }
 
     if isinstance(body, PostBodiesMultipleJsonBody):
+        _kwargs["json"] = UNSET
         if not isinstance(body, Unset):
             _kwargs["json"] = body.to_dict()
+        if isinstance(_kwargs["json"], Unset):
+            del _kwargs["json"]
+        elif _kwargs["json"] is None:
+            # HTTPX treats json=None as no body; send JSON null explicitly.
+            _kwargs["content"] = b"null"
+            del _kwargs["json"]
 
         headers["Content-Type"] = "application/json"
     if isinstance(body, File):

end_to_end_tests/golden-records/my-test-api-client/my_test_api_client/api/bodies/post_bodies_multiple.py

@@ -20,8 +20,15 @@ def _get_kwargs(
         "url": "/bodies/refs",
     }
 
+    _kwargs["json"] = UNSET
     if not isinstance(body, Unset):
         _kwargs["json"] = body.to_dict()
+    if isinstance(_kwargs["json"], Unset):
+        del _kwargs["json"]
+    elif _kwargs["json"] is None:
+        # HTTPX treats json=None as no body; send JSON null explicitly.
+        _kwargs["content"] = b"null"
+        del _kwargs["json"]
 
     headers["Content-Type"] = "application/json"
 

end_to_end_tests/golden-records/my-test-api-client/my_test_api_client/api/bodies/refs.py

@@ -19,8 +19,13 @@ def _get_kwargs(
         "url": "/config/content-type-override",
     }
 
-    if not isinstance(body, Unset):
-        _kwargs["json"] = body
+    _kwargs["json"] = body
+    if isinstance(_kwargs["json"], Unset):
+        del _kwargs["json"]
+    elif _kwargs["json"] is None:
+        # HTTPX treats json=None as no body; send JSON null explicitly.
+        _kwargs["content"] = b"null"
+        del _kwargs["json"]
 
     headers["Content-Type"] = "openapi/python/client"