fix: avoid orphan else in optional union JSON body transform

openapi_python_client/templates/property_templates/union_property.py.jinja

@@ -40,7 +40,7 @@ def _parse_{{ property.python_name }}(data: object) -> {{ property.get_type_stri
 {% endmacro %}
 
 {% macro transform(property, source, destination, declare_type=True, skip_unset=False) %}
-{% set ns = namespace(contains_properties_without_transform = false, contains_modified_properties = not property.required, has_if = false) %}
+{% set ns = namespace(contains_properties_without_transform = false, contains_modified_properties = not property.required and not skip_unset, has_if = false) %}
 {% if declare_type %}{{ destination }}: {{ property.get_type_string(json=True) | as_unembedded_code }}{% endif %}
 
 {% if not property.required and not skip_unset %}
@@ -59,18 +59,27 @@ if isinstance({{ source }}, Unset):
     {% if not ns.has_if %}
 if isinstance({{ source }}, {{ inner_property.get_instance_type_string() | as_unembedded_code }}):
         {% set ns.has_if = true %}
-    {% elif not loop.last or ns.contains_properties_without_transform %}
+    {% elif not loop.last or ns.contains_properties_without_transform or (not property.required and skip_unset) %}
 elif isinstance({{ source }}, {{ inner_property.get_instance_type_string() | as_unembedded_code }}):
     {% else %}
 else:
     {% endif %}
     {{ inner_template.transform(inner_property, source, destination, declare_type=False) | indent(4) }}
 {% endfor %}
 {% if ns.contains_properties_without_transform and ns.contains_modified_properties %}
+    {%- if not property.required and skip_unset %}
+elif not isinstance({{ source }}, Unset):
+    {%- else %}
 else:
+    {%- endif %}
     {{ destination }} = {{ source }}
 {%- elif ns.contains_properties_without_transform %}
+    {%- if not property.required and skip_unset %}
+if not isinstance({{ source }}, Unset):
+    {{ destination }} = {{ source }}
+    {%- else %}
 {{ destination }} = {{ source }}
+    {%- endif %}
 {%- endif %}
 {% endmacro %}
 

tests/test_templates/test_endpoint_macros.py

@@ -1,6 +1,22 @@
+import ast
 from types import SimpleNamespace
 
-from openapi_python_client.strings import PythonCode
+from jinja2 import Environment, PackageLoader
+
+from openapi_python_client import TEMPLATE_FILTERS
+from openapi_python_client.parser.properties import AnyProperty, DateTimeProperty, UnionProperty
+from openapi_python_client.strings import PythonCode, PythonIdentifier
+
+
+def _template_env() -> Environment:
+    env = Environment(
+        loader=PackageLoader("openapi_python_client"),
+        trim_blocks=True,
+        lstrip_blocks=True,
+        extensions=["jinja2.ext.loopcontrols"],
+    )
+    env.filters.update(TEMPLATE_FILTERS)
+    return env
 
 
 def _render_docstring(env, return_string, is_detailed: bool) -> str:
@@ -34,3 +50,68 @@ def test_endpoint_docstring_unwraps_python_code_return_string(env) -> None:
 
     assert "MyModel | None" in result
     assert "object at 0x" not in result
+
+
+def test_json_body_optional_union_without_transform_emits_valid_python() -> None:
+    """Optional union JSON body with only non-transformed members must not emit an orphan else."""
+    template = _template_env().get_template("endpoint_macros.py.jinja")
+    prop = UnionProperty(
+        name="body",
+        required=False,
+        default=None,
+        description=None,
+        example=None,
+        inner_properties=[
+            AnyProperty(
+                name="body_type_0",
+                required=True,
+                default=None,
+                description=None,
+                example=None,
+                python_name=PythonIdentifier(value="body_type_0", prefix="field_"),
+            )
+        ],
+        python_name=PythonIdentifier(value="body", prefix="field_"),
+    )
+    body = SimpleNamespace(prop=prop)
+
+    rendered = template.module.json_body(body).strip()
+    ast.parse(rendered)
+    assert rendered == 'if not isinstance(body, Unset):\n    _kwargs["json"] = body'
+
+
+def test_json_body_optional_union_with_mixed_transform_guards_unset() -> None:
+    """Optional union JSON body with transformed and non-transformed members must not fall into else for Unset."""
+    template = _template_env().get_template("endpoint_macros.py.jinja")
+    prop = UnionProperty(
+        name="body",
+        required=False,
+        default=None,
+        description=None,
+        example=None,
+        inner_properties=[
+            DateTimeProperty(
+                name="body_type_0",
+                required=True,
+                default=None,
+                description=None,
+                example=None,
+                python_name=PythonIdentifier(value="body_type_0", prefix="field_"),
+            ),
+            AnyProperty(
+                name="body_type_1",
+                required=True,
+                default=None,
+                description=None,
+                example=None,
+                python_name=PythonIdentifier(value="body_type_1", prefix="field_"),
+            ),
+        ],
+        python_name=PythonIdentifier(value="body", prefix="field_"),
+    )
+    body = SimpleNamespace(prop=prop)
+
+    rendered = template.module.json_body(body).strip()
+    ast.parse(rendered)
+    assert "elif not isinstance(body, Unset):" in rendered
+    assert "\nelse:" not in rendered