improvement: respect returning nested properties in python (#4236)

generators/python/core_utilities/sdk/http_client.py

@@ -140,7 +140,8 @@ def get_request_body(
         # If both data and json are None, we send json data in the event extra properties are specified
         json_body = maybe_filter_request_body(json, request_options, omit)
 
-    return json_body, data_body
+    # If you have an empty JSON body, you should just send None
+    return (json_body if json_body != {} else None), data_body if data_body != {} else None
 
 
 class HttpClient:

generators/python/sdk/CHANGELOG.md

@@ -5,6 +5,30 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [3.6.0] - 2024-08-08
+- Feat: The generator now respects returning nested properties, these can be specified via:
+
+  In OpenAPI below, we'd like to only return the property `jobId` from the `Job` object we get back from our server to our SDK users:
+  ```yaml
+  my/endpoint:
+    get:
+      x-fern-sdk-return-value: jobId
+      response: Job
+  ```
+  For a similar situation using the Fern definition:
+  ```yaml
+  endpoints:
+    getJob:
+      method: GET
+      path: my/endpoint
+      response:
+        type: Job
+        property: jobId
+  ```
+
+
+- Fix: The underlying content no longer sends empty JSON bodies, instead it'll pass a `None` value to httpx
+
 ## [3.5.1] - 2024-08-05
 
 - Fix: The root type for unions with visitors now has it's parent typed correctly. This allows auto-complete to work once again on the union when it's nested within other pydantic models.

generators/python/sdk/VERSION

@@ -1 +1 @@
-3.5.1
+3.6.0

generators/python/src/fern_python/generators/sdk/client_generator/endpoint_function_generator.py

@@ -2,7 +2,6 @@
 from typing import Dict, List, Optional, Set, Tuple, Union
 
 import fern.ir.resources as ir_types
-from typing_extensions import Never
 
 from fern_python.codegen import AST
 from fern_python.codegen.ast.ast_node.node_writer import NodeWriter
@@ -1020,9 +1019,25 @@ def _get_json_response_body_type(
             response=lambda response: self._context.pydantic_generator_context.get_type_hint_for_type_reference(
                 response.response_body_type,
             ),
-            nested_property_as_response=lambda _: raise_json_nested_property_as_response_unsupported(),
+            # TODO: What is the case where you have a nested property as response, but no response property configured?
+            nested_property_as_response=lambda response: self._get_nested_json_response_type(response),
         )
 
+    def _get_nested_json_response_type(self, response: ir_types.JsonResponseBodyWithProperty) -> AST.TypeHint:
+        response_type = self._context.pydantic_generator_context.get_type_hint_for_type_reference(
+            response.response_body_type
+        )
+        property_type = self._context.pydantic_generator_context.get_type_hint_for_type_reference(
+            response.response_property.value_type
+            if response.response_property is not None
+            else response.response_body_type
+        )
+
+        if response_type.is_optional and not property_type.is_optional:
+            return AST.TypeHint.optional(property_type)
+
+        return property_type
+
     def _get_streaming_response_body_type(
         self, *, stream_response: ir_types.StreamingResponse, is_async: bool
     ) -> AST.TypeHint:
@@ -1661,7 +1676,3 @@ def unwrap_optional_type(type_reference: ir_types.TypeReference) -> ir_types.Typ
         if container_as_union.type == "optional":
             return unwrap_optional_type(container_as_union.optional)
     return type_reference
-
-
-def raise_json_nested_property_as_response_unsupported() -> Never:
-    raise RuntimeError("nested property json response is unsupported")

generators/python/src/fern_python/generators/sdk/client_generator/endpoint_response_code_writer.py

@@ -1,7 +1,7 @@
 from typing import Callable, Optional
+from urllib import response
 
 import fern.ir.resources as ir_types
-from typing_extensions import Never
 
 from fern_python.codegen import AST
 from fern_python.external_dependencies.httpx_sse import HttpxSSE
@@ -158,6 +158,50 @@ def _handle_success_json(
                 else f"{EndpointResponseCodeWriter.RESPONSE_VARIABLE}.json()"
             ),
         )
+
+        # Validation rules limit the type of the response object to be either
+        # an object or optional object
+        property_access_expression: Optional[AST.Expression] = None
+        response_union = json_response.get_as_union()
+        if response_union.type == "nestedPropertyAsResponse":
+            response_body: ir_types.TypeReference = response_union.response_body_type
+            response_body_union = response_body.get_as_union()
+            response_property = (
+                response_union.response_property.name.name.snake_case.safe_name
+                if response_union.response_property is not None
+                else None
+            )
+            if response_body_union.type == "container":
+                response_container = response_body_union.container.get_as_union()
+                if response_container.type == "optional" and response_property is not None:
+                    property_access_expression = AST.Expression(
+                        f"{EndpointResponseCodeWriter.PARSED_RESPONSE_VARIABLE}.{response_property} if {EndpointResponseCodeWriter.PARSED_RESPONSE_VARIABLE} is not None else {EndpointResponseCodeWriter.PARSED_RESPONSE_VARIABLE}"
+                    )
+            elif response_body_union.type == "named":
+                response_named = self._context.pydantic_generator_context.get_declaration_for_type_id(
+                    response_body_union.type_id
+                )
+                property_access_expression = response_named.shape.visit(
+                    object=lambda _: AST.Expression(
+                        f"{EndpointResponseCodeWriter.PARSED_RESPONSE_VARIABLE}.{response_property}"
+                    ),
+                    alias=lambda _: None,
+                    enum=lambda _: None,
+                    union=lambda _: None,
+                    undiscriminated_union=lambda _: None,
+                )
+
+            if property_access_expression is not None:
+                # If you are indeed accessing a property, set the parsed response to an intermediate variable
+                writer.write_node(
+                    AST.VariableDeclaration(
+                        name=EndpointResponseCodeWriter.PARSED_RESPONSE_VARIABLE, initializer=pydantic_parse_expression
+                    )
+                )
+
+                # Then use the property accessed expression moving forward
+                pydantic_parse_expression = property_access_expression
+
         if self._pagination is not None:
             paginator = self._pagination.visit(
                 cursor=lambda cursor: CursorPagination(
@@ -404,7 +448,10 @@ def _get_json_response_body_type(
             response=lambda response: self._context.pydantic_generator_context.get_type_hint_for_type_reference(
                 response.response_body_type
             ),
-            nested_property_as_response=lambda _: raise_json_nested_property_as_response_unsupported(),
+            # TODO: What is the case where you have a nested property as response, but no response property configured?
+            nested_property_as_response=lambda response: self._context.pydantic_generator_context.get_type_hint_for_type_reference(
+                response.response_body_type
+            ),
         )
 
     def _get_streaming_response_data_type(self, streaming_response: ir_types.StreamingResponse) -> AST.TypeHint:
@@ -416,7 +463,3 @@ def _get_streaming_response_data_type(self, streaming_response: ir_types.Streami
         if union.type == "text":
             return AST.TypeHint.str_()
         raise RuntimeError(f"{union.type} streaming response is unsupported")
-
-
-def raise_json_nested_property_as_response_unsupported() -> Never:
-    raise RuntimeError("nested property json response is unsupported")

generators/python/src/fern_python/snippet/snippet_test_factory.py

@@ -462,6 +462,15 @@ def _generate_service_test(self, service: ir_types.HttpService, snippet_writer:
                         or endpoint.request_body.get_as_union().type == "bytes"
                     )
                 )
+                # TODO(FER-2852): support test generation for nested property responses
+                or (
+                    endpoint.response is not None
+                    and endpoint.response.body
+                    and (
+                        endpoint.response.body.get_as_union().type == "json"
+                        and endpoint.response.body.get_as_union().value.get_as_union().type == "nestedPropertyAsResponse"  # type: ignore
+                    )
+                )
             ):
                 continue
             endpoint_name = endpoint.name.snake_case.safe_name

generators/python/tests/utils/test_http_client.py

@@ -63,3 +63,24 @@ def test_get_none_request_body() -> None:
 
     assert json_body_extras == {"see you": "later"}
     assert data_body_extras is None
+
+def test_get_empty_json_request_body() -> None:
+    unrelated_request_options: RequestOptions = {"max_retries": 3}
+    json_body, data_body = get_request_body(
+        json=None,
+        data=None,
+        request_options=unrelated_request_options,
+        omit=None
+    )
+    assert json_body is None
+    assert data_body is None
+
+    json_body_extras, data_body_extras = get_request_body(
+        json={},
+        data=None,
+        request_options=unrelated_request_options,
+        omit=None
+    )
+
+    assert json_body_extras is None
+    assert data_body_extras is None