[python] backcompat tsp padding (#9017)

fix #9013

Related PR:
- [ ] Azure/azure-sdk-for-python#44084
- [x] #9019

---------

Co-authored-by: iscai-msft <isabellavcai@gmail.com>
Co-authored-by: Yuchao Yan <yuchaoyan@microsoft.com>

Author: 3 people

.chronus/changes/python-backcompatTspPadding-2025-10-18-17-23-22.md

@@ -0,0 +1,7 @@
+---
+changeKind: fix
+packages:
+  - "@typespec/http-client-python"
+---
+
+Keep original client name for backcompat reasons when the name is only padded for tsp generations

packages/http-client-python/generator/pygen/codegen/models/code_model.py

@@ -491,6 +491,14 @@ def _get_relative_generation_dir(self, root_dir: Path, namespace: str) -> Path:
     def has_operation_named_list(self) -> bool:
         return any(o.name.lower() == "list" for c in self.clients for og in c.operation_groups for o in og.operations)
 
+    @property
+    def has_padded_model_property(self) -> bool:
+        for model_type in self.model_types:
+            for prop in model_type.properties:
+                if prop.original_tsp_name:
+                    return True
+        return False
+
     @property
     def external_types(self) -> list[ExternalType]:
         """All of the external types"""

packages/http-client-python/generator/pygen/codegen/models/property.py

@@ -39,6 +39,7 @@ def __init__(
         self.flattened_names: list[str] = yaml_data.get("flattenedNames", [])
         self.is_multipart_file_input: bool = yaml_data.get("isMultipartFileInput", False)
         self.flatten = self.yaml_data.get("flatten", False) and not getattr(self.type, "flattened_property", False)
+        self.original_tsp_name: Optional[str] = self.yaml_data.get("originalTspName")
 
     def pylint_disable(self) -> str:
         retval: str = ""

packages/http-client-python/generator/pygen/codegen/serializers/model_serializer.py

@@ -333,6 +333,9 @@ def declare_property(self, prop: Property) -> str:
         if prop.xml_metadata:
             args.append(f"xml={prop.xml_metadata}")
 
+        if prop.original_tsp_name:
+            args.append(f'original_tsp_name="{prop.original_tsp_name}"')
+
         field = "rest_discriminator" if prop.is_discriminator else "rest_field"
         type_ignore = (
             "  # type: ignore"

packages/http-client-python/generator/pygen/codegen/templates/model_base.py.jinja2

@@ -662,6 +662,12 @@ class Model(_MyMutableMapping):
                 if not rf._rest_name_input:
                     rf._rest_name_input = attr
             cls._attr_to_rest_field: dict[str, _RestField] = dict(attr_to_rest_field.items())
+            {% if code_model.has_padded_model_property %}
+            cls._backcompat_attr_to_rest_field: dict[str, _RestField] = {
+                Model._get_backcompat_attribute_name(cls._attr_to_rest_field, attr): rf for attr, rf in cls
+                ._attr_to_rest_field.items()
+            }
+            {% endif %}
             cls._calculated.add(f"{cls.__module__}.{cls.__qualname__}")
 
         return super().__new__(cls)
@@ -671,6 +677,18 @@ class Model(_MyMutableMapping):
             if hasattr(base, "__mapping__"):
                 base.__mapping__[discriminator or cls.__name__] = cls  # type: ignore
 
+    {% if code_model.has_padded_model_property %}
+    @classmethod
+    def _get_backcompat_attribute_name(cls, attr_to_rest_field: dict[str, "_RestField"], attr_name: str) -> str:
+        rest_field_obj = attr_to_rest_field.get(attr_name)  # pylint: disable=protected-access
+        if rest_field_obj is None:
+            return attr_name
+        original_tsp_name = getattr(rest_field_obj, "_original_tsp_name", None)  # pylint: disable=protected-access
+        if original_tsp_name:
+            return original_tsp_name
+        return attr_name
+    {% endif %}
+
     @classmethod
     def _get_discriminator(cls, exist_discriminators) -> typing.Optional["_RestField"]:
         for v in cls.__dict__.values():
@@ -997,6 +1015,9 @@ def _failsafe_deserialize_xml(
       return None
 
 
+{% if code_model.has_padded_model_property %}
+# pylint: disable=too-many-instance-attributes
+{% endif %}
 class _RestField:
     def __init__(
         self,
@@ -1009,6 +1030,9 @@ class _RestField:
         format: typing.Optional[str] = None,
         is_multipart_file_input: bool = False,
         xml: typing.Optional[dict[str, typing.Any]] = None,
+        {% if code_model.has_padded_model_property %}
+        original_tsp_name: typing.Optional[str] = None,
+        {% endif %}
     ):
         self._type = type
         self._rest_name_input = name
@@ -1020,6 +1044,9 @@ class _RestField:
         self._format = format
         self._is_multipart_file_input = is_multipart_file_input
         self._xml = xml if xml is not None else {}
+        {% if code_model.has_padded_model_property %}
+        self._original_tsp_name = original_tsp_name
+        {% endif %}
 
     @property
     def _class_type(self) -> typing.Any:
@@ -1075,6 +1102,9 @@ def rest_field(
     format: typing.Optional[str] = None,
     is_multipart_file_input: bool = False,
     xml: typing.Optional[dict[str, typing.Any]] = None,
+    {% if code_model.has_padded_model_property %}
+    original_tsp_name: typing.Optional[str] = None,
+    {% endif %}
 ) -> typing.Any:
     return _RestField(
         name=name,
@@ -1084,6 +1114,9 @@ def rest_field(
         format=format,
         is_multipart_file_input=is_multipart_file_input,
         xml=xml,
+        {% if code_model.has_padded_model_property %}
+        original_tsp_name=original_tsp_name,
+        {% endif %}
     )
 
 

packages/http-client-python/generator/pygen/preprocess/__init__.py

@@ -236,7 +236,7 @@ def add_body_param_type(
                     body_parameter["type"]["types"].insert(1, any_obj_list_or_dict)
             code_model["types"].append(body_parameter["type"])
 
-    def pad_reserved_words(self, name: str, pad_type: PadType):
+    def pad_reserved_words(self, name: str, pad_type: PadType, yaml_type: dict[str, Any]) -> str:
         # we want to pad hidden variables as well
         if not name:
             # we'll pass in empty operation groups sometime etc.
@@ -250,26 +250,32 @@ def pad_reserved_words(self, name: str, pad_type: PadType):
         name_prefix = "_" if name[0] == "_" else ""
         name = name[1:] if name[0] == "_" else name
         if name.lower() in reserved_words[pad_type]:
+            if self.is_tsp and name.lower() in TSP_RESERVED_WORDS.get(pad_type, []):
+                # to maintain backcompat for cases where we pad in tsp but not in autorest,
+                # if we have a tsp reserved word, we also want to keep track of the original name for backcompat
+                yaml_type["originalTspName"] = name_prefix + name
             return name_prefix + name + pad_type
         return name_prefix + name
 
     def update_types(self, yaml_data: list[dict[str, Any]]) -> None:
         for type in yaml_data:
             for property in type.get("properties", []):
                 property["description"] = update_description(property.get("description", ""))
-                property["clientName"] = self.pad_reserved_words(property["clientName"].lower(), PadType.PROPERTY)
+                property["clientName"] = self.pad_reserved_words(
+                    property["clientName"].lower(), PadType.PROPERTY, property
+                )
                 add_redefined_builtin_info(property["clientName"], property)
             if type.get("name"):
                 pad_type = PadType.MODEL if type["type"] == "model" else PadType.ENUM_CLASS
-                name = self.pad_reserved_words(type["name"], pad_type)
+                name = self.pad_reserved_words(type["name"], pad_type, type)
                 type["name"] = name[0].upper() + name[1:]
                 type["description"] = update_description(type.get("description", ""), type["name"])
                 type["snakeCaseName"] = to_snake_case(type["name"])
             if type.get("values"):
                 # we're enums
                 values_to_add = []
                 for value in type["values"]:
-                    padded_name = self.pad_reserved_words(value["name"].lower(), PadType.ENUM_VALUE).upper()
+                    padded_name = self.pad_reserved_words(value["name"].lower(), PadType.ENUM_VALUE, value).upper()
                     if self.version_tolerant:
                         if padded_name[0] in "0123456789":
                             padded_name = "ENUM_" + padded_name
@@ -364,12 +370,14 @@ def get_operation_updater(self, yaml_data: dict[str, Any]) -> Callable[[dict[str
     def update_parameter(self, yaml_data: dict[str, Any]) -> None:
         yaml_data["description"] = update_description(yaml_data.get("description", ""))
         if not (yaml_data["location"] == "header" and yaml_data["clientName"] in ("content_type", "accept")):
-            yaml_data["clientName"] = self.pad_reserved_words(yaml_data["clientName"].lower(), PadType.PARAMETER)
+            yaml_data["clientName"] = self.pad_reserved_words(
+                yaml_data["clientName"].lower(), PadType.PARAMETER, yaml_data
+            )
         if yaml_data.get("propertyToParameterName"):
             # need to create a new one with padded keys and values
             yaml_data["propertyToParameterName"] = {
-                self.pad_reserved_words(prop, PadType.PROPERTY): self.pad_reserved_words(
-                    param_name, PadType.PARAMETER
+                self.pad_reserved_words(prop, PadType.PROPERTY, yaml_data): self.pad_reserved_words(
+                    param_name, PadType.PARAMETER, yaml_data
                 ).lower()
                 for prop, param_name in yaml_data["propertyToParameterName"].items()
             }
@@ -390,15 +398,17 @@ def update_operation(
         *,
         is_overload: bool = False,
     ) -> None:
-        yaml_data["groupName"] = self.pad_reserved_words(yaml_data["groupName"], PadType.OPERATION_GROUP)
+        yaml_data["groupName"] = self.pad_reserved_words(yaml_data["groupName"], PadType.OPERATION_GROUP, yaml_data)
         yaml_data["groupName"] = to_snake_case(yaml_data["groupName"])
         yaml_data["name"] = yaml_data["name"].lower()
         if yaml_data.get("isLroInitialOperation") is True:
             yaml_data["name"] = (
-                "_" + self.pad_reserved_words(extract_original_name(yaml_data["name"]), PadType.METHOD) + "_initial"
+                "_"
+                + self.pad_reserved_words(extract_original_name(yaml_data["name"]), PadType.METHOD, yaml_data)
+                + "_initial"
             )
         else:
-            yaml_data["name"] = self.pad_reserved_words(yaml_data["name"], PadType.METHOD)
+            yaml_data["name"] = self.pad_reserved_words(yaml_data["name"], PadType.METHOD, yaml_data)
         yaml_data["description"] = update_description(yaml_data["description"], yaml_data["name"])
         yaml_data["summary"] = update_description(yaml_data.get("summary", ""))
         body_parameter = yaml_data.get("bodyParameter")
@@ -485,7 +495,7 @@ def update_paging_operation(
         item_type = item_type or yaml_data["itemType"]["elementType"]
         if yaml_data.get("nextOperation"):
             yaml_data["nextOperation"]["groupName"] = self.pad_reserved_words(
-                yaml_data["nextOperation"]["groupName"], PadType.OPERATION_GROUP
+                yaml_data["nextOperation"]["groupName"], PadType.OPERATION_GROUP, yaml_data["nextOperation"]
             )
             yaml_data["nextOperation"]["groupName"] = to_snake_case(yaml_data["nextOperation"]["groupName"])
             for response in yaml_data["nextOperation"].get("responses", []):
@@ -503,10 +513,11 @@ def update_operation_groups(self, code_model: dict[str, Any], client: dict[str,
             operation_group["identifyName"] = self.pad_reserved_words(
                 operation_group.get("name", operation_group["propertyName"]),
                 PadType.OPERATION_GROUP,
+                operation_group,
             )
             operation_group["identifyName"] = to_snake_case(operation_group["identifyName"])
             operation_group["propertyName"] = self.pad_reserved_words(
-                operation_group["propertyName"], PadType.OPERATION_GROUP
+                operation_group["propertyName"], PadType.OPERATION_GROUP, operation_group
             )
             operation_group["propertyName"] = to_snake_case(operation_group["propertyName"])
             operation_group["className"] = update_operation_group_class_name(

packages/http-client-python/generator/test/unittests/test_name_converter.py

@@ -8,7 +8,7 @@
 
 
 def pad_reserved_words(name: str, pad_type: PadType) -> str:
-    return PreProcessPlugin(output_folder="").pad_reserved_words(name, pad_type)
+    return PreProcessPlugin(output_folder="").pad_reserved_words(name, pad_type, {})
 
 
 def test_escaped_reserved_words():