Fix Python ETag preprocessing for nested operation groups

.chronus/changes/fix-required-etag-header-2026-09-14.md

@@ -0,0 +1,7 @@
+---
+changeKind: fix
+packages:
+  - "@typespec/http-client-python"
+---
+
+Generate complete ETag handling for operations in nested operation groups.

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

@@ -264,9 +264,6 @@ def _process_operation_etag_headers(
     if_match_candidates: list[dict[str, Any]] = []
     if_none_match_candidates: list[dict[str, Any]] = []
     for p in operation["parameters"]:
-        wire_name_lower = get_wire_name_lower(p)
-        if p["location"] == "header" and wire_name_lower == "client-request-id":
-            client["requestIdHeaderName"] = wire_name_lower
         if version_tolerant and p["location"] == "header":
             role = _get_etag_role(p)
             if role == "ifMatch":
@@ -275,7 +272,6 @@ def _process_operation_etag_headers(
                 if_none_match_candidates.append(p)
 
     property_if_match, property_if_none_match = _resolve_etag_pair(if_match_candidates, if_none_match_candidates)
-
     if property_if_match and property_if_none_match:
         etag_params = {id(property_if_match), id(property_if_none_match)}
         operation["parameters"] = [item for item in operation["parameters"] if id(item) not in etag_params] + [
@@ -286,6 +282,21 @@ def _process_operation_etag_headers(
         client["hasEtag"] = True
 
 
+def _process_operation_group_etag_headers(
+    operation_groups: list[dict[str, Any]],
+    client: dict[str, Any],
+    version_tolerant: bool,
+) -> None:
+    for operation_group in operation_groups:
+        for operation in operation_group.get("operations", []):
+            _process_operation_etag_headers(operation, client, version_tolerant)
+        _process_operation_group_etag_headers(
+            operation_group.get("operationGroups", []),
+            client,
+            version_tolerant,
+        )
+
+
 def headers_convert(yaml_data: dict[str, Any], replace_data: Any) -> None:
     if isinstance(replace_data, dict):
         for k, v in replace_data.items():
@@ -607,9 +618,16 @@ def update_client(self, yaml_data: dict[str, Any]) -> None:
         if prop_name.endswith("Client"):
             prop_name = prop_name[: len(prop_name) - len("Client")]
         yaml_data["builderPadName"] = to_snake_case(prop_name)
-        for og in yaml_data.get("operationGroups", []):
-            for o in og["operations"]:
-                _process_operation_etag_headers(o, yaml_data, self.version_tolerant)
+        for operation_group in yaml_data.get("operationGroups", []):
+            for operation in operation_group.get("operations", []):
+                for parameter in operation["parameters"]:
+                    if parameter["location"] == "header" and get_wire_name_lower(parameter) == "client-request-id":
+                        yaml_data["requestIdHeaderName"] = "client-request-id"
+        _process_operation_group_etag_headers(
+            yaml_data.get("operationGroups", []),
+            yaml_data,
+            self.version_tolerant,
+        )
 
         # add client signature cloud_setting for arm
         if self.azure_arm and yaml_data["parameters"]:

packages/http-client-python/tests/unit/test_preprocess_etag.py

@@ -20,12 +20,18 @@ def _plugin() -> PreProcessPlugin:
     )
 
 
-def _header_param(client_name: str, wire_name: str, etag_role: str | None) -> dict:
+def _header_param(
+    client_name: str,
+    wire_name: str,
+    etag_role: str | None,
+    *,
+    optional: bool = True,
+) -> dict:
     p: dict = {
         "clientName": client_name,
         "wireName": wire_name,
         "location": "header",
-        "optional": True,
+        "optional": optional,
         "implementation": "Method",
         "type": {"type": "string"},
     }
@@ -59,6 +65,49 @@ def _get_op(client: dict) -> dict:
     return client["operationGroups"][0]["operations"][0]
 
 
+def test_etag_headers_in_nested_operation_group_are_processed():
+    """Nested ETag operations get their partner parameter and enable client helpers."""
+    if_match = _header_param(
+        "if_match",
+        "If-Match",
+        "ifMatch",
+        optional=False,
+    )
+    operation = {
+        "name": "remove",
+        "parameters": [if_match],
+    }
+    client = _client_yaml([])
+    parent_group = {
+        "operations": [],
+        "operationGroups": [
+            {
+                "operations": [operation],
+            }
+        ],
+    }
+    client["operationGroups"] = [parent_group]
+
+    plugin = _plugin()
+    plugin.update_client(client)
+
+    assert client["hasEtag"] is True
+    assert "hasEtag" not in parent_group
+    assert operation["hasEtag"] is True
+    assert len(operation["parameters"]) == 2
+    assert operation["parameters"][0]["etagRole"] == "ifMatch"
+    assert operation["parameters"][1]["etagRole"] == "ifNoneMatch"
+    assert all(parameter["optional"] is False for parameter in operation["parameters"])
+    assert all("clientDefaultValue" not in parameter for parameter in operation["parameters"])
+
+    for parameter in operation["parameters"]:
+        plugin.update_parameter(parameter)
+    assert [parameter["clientName"] for parameter in operation["parameters"]] == [
+        "etag",
+        "match_condition",
+    ]
+
+
 def test_etag_role_preserved_when_only_standard_pair_present():
     """Standard If-Match/If-None-Match keep their etagRole."""
     if_match = _header_param("if_match", "If-Match", "ifMatch")