Include exception message in ErrorAnalysisCard subtitle

ax/analysis/analysis.py

@@ -206,10 +206,18 @@ def error_card_from_analysis_e(
     analysis_name = analysis_e.analysis.__class__.__name__
     exception_name = analysis_e.exception.__class__.__name__
 
+    # Include the exception message in the subtitle if available, so users can
+    # see the reasoning in the error card.
+    subtitle = (
+        f"{exception_name}: {exception_message}"
+        if (exception_message := str(analysis_e.exception))
+        else f"{exception_name} encountered while computing {analysis_name}."
+    )
+
     return ErrorAnalysisCard(
         name=analysis_name,
         title=f"{analysis_name} Error",
-        subtitle=f"{exception_name} encountered while computing {analysis_name}.",
+        subtitle=subtitle,
         df=pd.DataFrame(),
         blob=analysis_e.tb_str() or "",
     )

ax/analysis/tests/test_analysis.py

@@ -0,0 +1,37 @@
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+#
+# This source code is licensed under the MIT license found in the
+# LICENSE file in the root directory of this source tree.
+
+# pyre-strict
+
+from ax.analysis.analysis import AnalysisE, error_card_from_analysis_e
+from ax.analysis.plotly.parallel_coordinates import ParallelCoordinatesPlot
+from ax.utils.common.testutils import TestCase
+
+
+class AnalysisTest(TestCase):
+    def test_error_card_from_analysis_e(self) -> None:
+        for exception, expected_subtitle in (
+            (
+                ValueError("something went wrong"),
+                "ValueError: something went wrong",
+            ),
+            (
+                ValueError(),
+                "ValueError encountered while computing ParallelCoordinatesPlot.",
+            ),
+        ):
+            with self.subTest(exception=exception):
+                analysis_e = AnalysisE(
+                    message="test",
+                    exception=exception,
+                    analysis=ParallelCoordinatesPlot(),
+                )
+
+                card = error_card_from_analysis_e(analysis_e)
+
+                self.assertEqual(card.name, "ParallelCoordinatesPlot")
+                self.assertEqual(card.title, "ParallelCoordinatesPlot Error")
+                self.assertEqual(card.subtitle, expected_subtitle)
+                self.assertIn("ValueError", card.blob)

ax/api/tests/test_client.py

@@ -23,7 +23,6 @@
 from ax.api.protocols.metric import IMetric
 from ax.api.protocols.runner import IRunner
 from ax.api.types import TParameterization
-from ax.core.analysis_card import AnalysisCard
 from ax.core.data import Data
 from ax.core.experiment import Experiment
 from ax.core.map_metric import MapMetric
@@ -1280,12 +1279,7 @@ def test_compute_analyses(self) -> None:
         self.assertEqual(cards[0].title, "ParallelCoordinatesPlot Error")
         self.assertEqual(
             cards[0].subtitle,
-            "AnalysisNotApplicableStateError encountered while computing "
-            "ParallelCoordinatesPlot.",
-        )
-        self.assertIn(
-            "Experiment has no trials",
-            assert_is_instance(cards[0], AnalysisCard).blob,
+            "AnalysisNotApplicableStateError: Experiment has no trials.",
         )
 
         for trial_index, _ in client.get_next_trials(max_trials=1).items():