feat: Populate AppDetails to each Invocation

AppDetails require two pieces of information:
1) Instructions
2) Tools

Both these pieces of information are gathered using the llm_request that was passed to the model. This approach, slightly invasive, ensures that we capture the "exact" instructions and tools that were given to the model.

PiperOrigin-RevId: 811180648

tests/unittests/evaluation/test_request_intercepter_plugin.py

@@ -0,0 +1,73 @@
+# Copyright 2025 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.
+
+from __future__ import annotations
+
+from unittest import mock
+
+from google.adk.agents.callback_context import CallbackContext
+from google.adk.evaluation.request_intercepter_plugin import _LLM_REQUEST_ID_KEY
+from google.adk.evaluation.request_intercepter_plugin import _RequestIntercepterPlugin
+from google.adk.models.llm_request import LlmRequest
+from google.adk.models.llm_response import LlmResponse
+from google.genai import types
+
+
+class TestRequestIntercepterPlugin:
+
+  async def test_intercept_request_and_response(self):
+    plugin = _RequestIntercepterPlugin(name="test_plugin")
+    llm_request = LlmRequest(
+        model="test_model",
+        contents=[
+            types.Content(
+                role="user",
+                parts=[types.Part(text="hello")],
+            )
+        ],
+    )
+    mock_invocation_context = mock.MagicMock()
+    mock_invocation_context.session.state = {}
+    callback_context = CallbackContext(mock_invocation_context)
+    llm_response = LlmResponse()
+
+    # Test before_model_callback
+    await plugin.before_model_callback(
+        callback_context=callback_context, llm_request=llm_request
+    )
+    assert _LLM_REQUEST_ID_KEY in callback_context.state
+    request_id = callback_context.state[_LLM_REQUEST_ID_KEY]
+    assert isinstance(request_id, str)
+
+    # Test after_model_callback
+    await plugin.after_model_callback(
+        callback_context=callback_context, llm_response=llm_response
+    )
+    assert llm_response.custom_metadata is not None
+    assert _LLM_REQUEST_ID_KEY in llm_response.custom_metadata
+    assert llm_response.custom_metadata[_LLM_REQUEST_ID_KEY] == request_id
+
+    # Test get_model_request
+    retrieved_request = plugin.get_model_request(llm_response)
+    assert retrieved_request == llm_request
+
+  def test_get_model_request_not_found(self):
+    plugin = _RequestIntercepterPlugin(name="test_plugin")
+    llm_response = LlmResponse()
+    assert plugin.get_model_request(llm_response) is None
+
+    llm_response_with_metadata = LlmResponse(
+        custom_metadata={_LLM_REQUEST_ID_KEY: "non_existent_id"}
+    )
+    assert plugin.get_model_request(llm_response_with_metadata) is None