feat: Update the interface for custom code execution metric while maintaining remote_custom_function support for backward compatibility

tests/unit/vertexai/genai/replays/test_custom_code_execution_metric.py

@@ -18,22 +18,32 @@
 from vertexai._genai import types
 from google.genai import types as genai_types
 import pandas as pd
+import pytest
 
 
-def test_custom_code_execution(client):
-    """Tests that custom code execution metric produces a correctly structured EvaluationResult."""
-
-    code_snippet = """
+CODE_SNIPPET = """
 def evaluate(instance):
     if instance['response'] == instance['reference']:
         return 1.0
     return 0.0
 """
 
-    custom_metric = types.Metric(
-        name="my_custom_code_metric",
-        remote_custom_function=code_snippet,
-    )
+
+@pytest.mark.parametrize(
+    "custom_metric",
+    [
+        types.CodeExecutionMetric(
+            name="my_custom_code_metric",
+            custom_function=CODE_SNIPPET,
+        ),
+        types.Metric(
+            name="my_custom_code_metric",
+            remote_custom_function=CODE_SNIPPET,
+        ),
+    ],
+)
+def test_custom_code_execution(client, custom_metric):
+    """Tests that custom code execution metric produces a correctly structured EvaluationResult."""
 
     prompts_df = pd.DataFrame(
         {
@@ -69,21 +79,22 @@ def evaluate(instance):
         assert case_result.response_candidate_results is not None
 
 
-def test_custom_code_execution_batch_evaluate(client):
+@pytest.mark.parametrize(
+    "custom_metric",
+    [
+        types.CodeExecutionMetric(
+            name="my_custom_code_metric",
+            custom_function=CODE_SNIPPET,
+        ),
+        types.Metric(
+            name="my_custom_code_metric",
+            remote_custom_function=CODE_SNIPPET,
+        ),
+    ],
+)
+def test_custom_code_execution_batch_evaluate(client, custom_metric):
     """Tests that batch_evaluate() works with custom code execution metric."""
 
-    code_snippet = """
-def evaluate(instance):
-    if instance['response'] == instance['reference']:
-        return 1.0
-    return 0.0
-"""
-
-    custom_metric = types.Metric(
-        name="my_custom_code_metric",
-        remote_custom_function=code_snippet,
-    )
-
     eval_dataset = types.EvaluationDataset(
         gcs_source=genai_types.GcsSource(
             uris=["gs://genai-eval-sdk-replay-test/test_data/inference_results.jsonl"]

vertexai/_genai/_evals_metric_handlers.py

@@ -845,7 +845,7 @@ def get_metric_result(
         score = None
         explanation = None
         try:
-            if self.metric.custom_function:
+            if self.metric.custom_function and callable(self.metric.custom_function):
                 custom_function_result = self.metric.custom_function(
                     instance_for_custom_fn
                 )
@@ -1058,10 +1058,10 @@ def metric_name(self) -> str:
     def __init__(self, module: "evals.Evals", metric: types.Metric):
         super().__init__(module=module, metric=metric)
 
-        if not self.metric.remote_custom_function:
+        if not self.metric.remote_custom_function and not self.metric.custom_function:
             raise ValueError(
                 f"CustomCodeExecutionMetricHandler for '{self.metric.name}' needs "
-                " Metric.remote_custom_function to be set."
+                " custom function to be set."
             )
 
     def _build_request_payload(
@@ -1310,7 +1310,17 @@ def aggregate(
 
 _METRIC_HANDLER_MAPPING = [
     (
-        lambda m: hasattr(m, "remote_custom_function") and m.remote_custom_function,
+        lambda m: (
+            # Recognize the user-facing class
+            isinstance(m, types.CodeExecutionMetric)
+            and (hasattr(m, "custom_function") and m.custom_function)
+        )
+        or (hasattr(m, "remote_custom_function") and m.remote_custom_function)
+        # Recognize base Metric objects that have been coerced by Pydantic
+        or (
+            isinstance(m, types.Metric)
+            and isinstance(getattr(m, "custom_function", None), str)
+        ),
         CustomCodeExecutionMetricHandler,
     ),
     (

vertexai/_genai/_evals_metric_loaders.py

@@ -370,3 +370,12 @@ def GECKO_TEXT2VIDEO(self) -> LazyLoadedPrebuiltMetric:
 
 PrebuiltMetric = PrebuiltMetricLoader()
 RubricMetric = PrebuiltMetric
+
+
+def CodeExecutionMetric(
+    name: str, custom_function: str, **kwargs: Any
+) -> "types.Metric":
+    """Instantiates a code execution metric."""
+    from . import types
+
+    return types.Metric(name=name, remote_custom_function=custom_function, **kwargs)

vertexai/_genai/_transformers.py

@@ -73,6 +73,16 @@ def t_metrics(
             metric_payload_item["custom_code_execution_spec"] = {
                 "evaluation_function": metric.remote_custom_function
             }
+        elif (
+            isinstance(metric, types.CodeExecutionMetric)
+            or (
+                isinstance(metric, types.Metric)
+                and isinstance(getattr(metric, "custom_function", None), str)
+            )
+        ) and getattr(metric, "custom_function", None):
+            metric_payload_item["custom_code_execution_spec"] = {
+                "evaluation_function": metric.custom_function
+            }
         # LLM-based metrics
         elif hasattr(metric, "prompt_template") and metric.prompt_template:
             llm_based_spec: dict[str, Any] = {
@@ -196,6 +206,16 @@ def t_metric_for_registry(
         metric_payload_item["custom_code_execution_spec"] = {
             "evaluation_function": metric.remote_custom_function
         }
+    elif (
+        isinstance(metric, types.CodeExecutionMetric)
+        or (
+            isinstance(metric, types.Metric)
+            and isinstance(getattr(metric, "custom_function", None), str)
+        )
+    ) and getattr(metric, "custom_function", None):
+        metric_payload_item["custom_code_execution_spec"] = {
+            "evaluation_function": metric.custom_function
+        }
 
     # Map LLM-based metrics to the new llm_based_metric_spec
     elif (hasattr(metric, "prompt_template") and metric.prompt_template) or (

vertexai/_genai/types/__init__.py

@@ -207,6 +207,7 @@
 from .common import Chunk
 from .common import ChunkDict
 from .common import ChunkOrDict
+from .common import CodeExecutionMetric
 from .common import CometResult
 from .common import CometResultDict
 from .common import CometResultOrDict
@@ -2153,6 +2154,7 @@
     "PromptDataDict",
     "PromptDataOrDict",
     "LLMMetric",
+    "CodeExecutionMetric",
     "MetricPromptBuilder",
     "RubricContentProperty",
     "RubricContentPropertyDict",

vertexai/_genai/types/common.py

@@ -1576,7 +1576,7 @@ class Metric(_common.BaseModel):
     """The metric used for evaluation."""
 
     name: Optional[str] = Field(default=None, description="""The name of the metric.""")
-    custom_function: Optional[Callable[..., Any]] = Field(
+    custom_function: Optional[Union[str, Callable[..., Any]]] = Field(
         default=None,
         description="""The custom function that defines the end-to-end logic for metric computation.""",
     )
@@ -1682,6 +1682,26 @@ def to_yaml_file(self, file_path: str, version: Optional[str] = None) -> None:
             yaml.dump(data_to_dump, f, sort_keys=False, allow_unicode=True)
 
 
+class CodeExecutionMetric(Metric):
+    """A metric that executes custom Python code for evaluation."""
+
+    # You can use standard Pydantic Field syntax here because this is raw Python code
+    custom_function: Optional[str] = Field(
+        default=None,
+        description="""The Python function code to be executed on the server side.""",
+    )
+
+    # You can also add hand-written validators or methods here
+    @field_validator("custom_function")
+    @classmethod
+    def validate_code(cls, value: Optional[str]) -> Optional[str]:
+        if value and "def evaluate" not in value:
+            raise ValueError(
+                "custom_function must contain a 'def evaluate(instance):' signature."
+            )
+        return value
+
+
 class LLMMetric(Metric):
     """A metric that uses LLM-as-a-judge for evaluation."""
 
@@ -1792,7 +1812,7 @@ class MetricDict(TypedDict, total=False):
     name: Optional[str]
     """The name of the metric."""
 
-    custom_function: Optional[Callable[..., Any]]
+    custom_function: Optional[Union[str, Callable[..., Any]]]
     """The custom function that defines the end-to-end logic for metric computation."""
 
     prompt_template: Optional[str]