Add handling of no metrics response

simvue/client.py

@@ -1099,6 +1099,9 @@ def get_metric_values(
             max_points=max_points or -1,
         )
 
+        if not run_metrics:
+            return None
+
         if aggregate:
             return aggregated_metrics_to_dataframe(
                 run_metrics, xaxis=xaxis, parse_to=output_format
@@ -1156,6 +1159,12 @@ def plot_metrics(
             aggregate=False,
         )
 
+        if data is None:
+            raise RuntimeError(
+                f"Cannot plot metrics {metric_names}, "
+                f"no data found for runs {run_ids}."
+            )
+
         # Undo multi-indexing
         flattened_df = data.reset_index()
 

simvue/converters.py

@@ -120,6 +120,12 @@ def parse_run_set_metrics(
     ValueError
         if an unrecognised parse format is specified
     """
+    if not request_response_data:
+        if parse_to == "dataframe":
+            return pandas.DataFrame({})
+        else:
+            return {}
+
     _all_steps: list[float] = sorted(
         set(
             (