feat(api_core): add request-id auto-population logic to gapic_v1 public helpers (#17738)

Introduces `requests` module containing `setup_request_id` helper.
Exposes the module as public in `gapic_v1`.

The unit tests in
[test_method_helpers.py](https://github.com/googleapis/google-cloud-python/blob/feat/gapic-centralization-api-core-request-id/packages/google-api-core/tests/unit/gapic/test_method_helpers.py#L20-L119)
are now identical to the generator's original test template
[test_service.py.j2](https://github.com/googleapis/google-cloud-python/blob/main/packages/gapic-generator/gapic/templates/tests/unit/gapic/%25name_%25version/%25sub/test_%25service.py.j2#L437-L514)
(with the exception of our added None request test case).

Author: hebaalazzeh

packages/google-api-core/google/api_core/gapic_v1/__init__.py

@@ -25,9 +25,10 @@
 # Older Python versions safely ignore this variable.
 __lazy_modules__: Set[str] = {
     "google.api_core.gapic_v1.client_info",
+    "google.api_core.gapic_v1.requests",
     "google.api_core.gapic_v1.routing_header",
 }
-__all__ = ["client_info", "routing_header"]
+__all__ = ["client_info", "requests", "routing_header"]
 
 if _has_grpc:
     __lazy_modules__.update(
@@ -41,6 +42,7 @@
 
 from google.api_core.gapic_v1 import (  # noqa: E402
     client_info,
+    requests,
     routing_header,
 )
 

packages/google-api-core/google/api_core/gapic_v1/requests.py

@@ -0,0 +1,72 @@
+# -*- coding: utf-8 -*-
+# Copyright 2026 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+"""Helpers for preparing and structuring API requests.
+
+This module provides utilities to preprocess request parameters and objects
+before invoking API methods, such as automatically generating request IDs
+if they are not already set.
+"""
+
+from typing import Union
+import uuid
+
+import google.protobuf.message
+
+
+def setup_request_id(
+    request: Union[google.protobuf.message.Message, dict, None],
+    field_name: str,
+    is_proto3_optional: bool,
+) -> None:
+    """Populate a UUID4 field in the request if it is not already set.
+
+    This helper is used to ensure request idempotency by automatically
+    generating a unique identifier (such as `request_id`) for requests
+    that support it. If a request is retried, the same identifier can be
+    sent on subsequent retries, allowing the server to recognize the retried
+    request and prevent duplicate processing (e.g., creating duplicate
+    resources).
+
+    Args:
+        request (Union[google.protobuf.message.Message, dict]): The
+            request object.
+        field_name (str): The name of the field to populate.
+        is_proto3_optional (bool): Whether the field is proto3 optional.
+    """
+    if request is None:
+        return
+
+    if isinstance(request, dict):
+        if is_proto3_optional:
+            if field_name not in request or request[field_name] is None:
+                request[field_name] = str(uuid.uuid4())
+        elif not request.get(field_name):
+            request[field_name] = str(uuid.uuid4())
+        return
+
+    if is_proto3_optional:
+        try:
+            # Pure protobuf messages
+            if not request.HasField(field_name):
+                setattr(request, field_name, str(uuid.uuid4()))
+        except (AttributeError, ValueError):
+            # Proto-plus messages or other objects
+            if not getattr(request, field_name, None):
+                setattr(request, field_name, str(uuid.uuid4()))
+    else:
+        if not getattr(request, field_name, None):
+            setattr(request, field_name, str(uuid.uuid4()))

packages/google-api-core/tests/unit/gapic/test_requests.py

@@ -0,0 +1,116 @@
+# -*- coding: utf-8 -*-
+# Copyright 2026 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import re
+
+import pytest
+
+from google.api_core.gapic_v1.requests import setup_request_id
+
+
+# --- Mock Request Helper Classes ---
+
+
+class MockRequest:
+    def __init__(self, **kwargs):
+        for k, v in kwargs.items():
+            setattr(self, k, v)
+
+    def __contains__(self, key):
+        return hasattr(self, key)
+
+
+class MockProtoRequest:
+    def __init__(self, **kwargs):
+        for k, v in kwargs.items():
+            setattr(self, k, v)
+
+    def HasField(self, key):
+        return hasattr(self, key)
+
+
+class MockValueErrorRequest:
+    def HasField(self, key):
+        raise ValueError("Mismatched field")
+
+    def __contains__(self, key):
+        return hasattr(self, key)
+
+
+# --- Parameterized Test ---
+
+UUID_REGEX = r"[0-9a-f]{8}-[0-9a-f]{4}-4[0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}"
+
+
+@pytest.mark.parametrize(
+    "request_obj, is_proto3_optional, expected",
+    [
+        # MockRequest cases
+        (MockRequest(), True, "uuid"),
+        (MockRequest(request_id="already_set"), True, "already_set"),
+        (MockRequest(request_id=""), False, "uuid"),
+        (MockRequest(request_id="already_set"), False, "already_set"),
+        # MockProtoRequest cases
+        (MockProtoRequest(), True, "uuid"),
+        (MockProtoRequest(request_id="already_set"), True, "already_set"),
+        # ValueError case
+        (MockValueErrorRequest(), True, "uuid"),
+        # Dict cases
+        ({}, True, "uuid"),
+        ({"request_id": None}, True, "uuid"),
+        ({"request_id": "already_set"}, True, "already_set"),
+        ({"request_id": ""}, False, "uuid"),
+        ({"request_id": None}, False, "uuid"),
+        ({"request_id": "already_set"}, False, "already_set"),
+        # None case
+        (None, True, "none"),
+    ],
+    ids=[
+        "proto3_optional_not_in_request",
+        "proto3_optional_already_in_request",
+        "non_proto3_optional_empty",
+        "non_proto3_optional_already_set",
+        "proto3_optional_not_in_request_proto",
+        "proto3_optional_already_in_request_proto",
+        "value_error_fallback",
+        "dict_proto3_optional_not_in_request",
+        "dict_proto3_optional_value_none",
+        "dict_proto3_optional_already_in_request",
+        "dict_non_proto3_optional_empty",
+        "dict_non_proto3_optional_value_none",
+        "dict_non_proto3_optional_already_set",
+        "none_request",
+    ],
+)
+def test_setup_request_id(request_obj, is_proto3_optional, expected):
+    # Act
+    setup_request_id(request_obj, "request_id", is_proto3_optional)
+
+    # Assert
+    if expected == "none":
+        assert request_obj is None
+        return
+
+    # Extract the resulting value depending on container type
+    value = (
+        request_obj["request_id"]
+        if isinstance(request_obj, dict)
+        else request_obj.request_id
+    )
+
+    if expected == "uuid":
+        assert re.match(UUID_REGEX, value)
+    else:
+        assert value == expected