fix: Raise an error when CrossValidationReport fails before at least one estimator is fitted

skore/src/skore/sklearn/_cross_validation/report.py

@@ -29,15 +29,18 @@ def _generate_estimator_report(
     y: Optional[ArrayLike],
     train_indices: ArrayLike,
     test_indices: ArrayLike,
-) -> EstimatorReport:
-    return EstimatorReport(
-        estimator,
-        fit=True,
-        X_train=_safe_indexing(X, train_indices),
-        y_train=_safe_indexing(y, train_indices),
-        X_test=_safe_indexing(X, test_indices),
-        y_test=_safe_indexing(y, test_indices),
-    )
+) -> Union[EstimatorReport, KeyboardInterrupt, Exception]:
+    try:
+        return EstimatorReport(
+            estimator,
+            fit=True,
+            X_train=_safe_indexing(X, train_indices),
+            y_train=_safe_indexing(y, train_indices),
+            X_test=_safe_indexing(X, test_indices),
+            y_test=_safe_indexing(y, test_indices),
+        )
+    except (KeyboardInterrupt, Exception) as e:
+        return e
 
 
 class CrossValidationReport(_BaseReport, DirNamesMixin):
@@ -198,31 +201,55 @@ def _fit_estimator_reports(self) -> list[EstimatorReport]:
         )
 
         estimator_reports = []
-        try:
-            for report in generator:
-                estimator_reports.append(report)
-                progress.update(task, advance=1, refresh=True)
-        except (Exception, KeyboardInterrupt) as e:
-            from skore import console  # avoid circular import
+        for report in generator:
+            estimator_reports.append(report)
+            progress.update(task, advance=1, refresh=True)
+
+        warn_msg = None
+        if not any (
+            isinstance(report, EstimatorReport)
+            for report in estimator_reports
+        ):
+            traceback_msg = "\n".join(str(exc) for exc in estimator_reports)
+            raise RuntimeError(
+                "Cross-validation failed: no estimators were successfully fitted. "
+                "Please check your data, estimator, or cross-validation setup.\n"
+                f"Traceback: \n{traceback_msg}"
+            )
+        elif any(isinstance(report, Exception) for report in estimator_reports):
+            msg_traceback = "\n".join(
+                str(exc) for exc in estimator_reports if isinstance(exc, Exception)
+            )
+            warn_msg = (
+                "Cross-validation process was interrupted by an error before "
+                "all estimators could be fitted; CrossValidationReport object "
+                "might not contain all the expected results.\n"
+                f"Traceback: \n{msg_traceback}"
+            )
+            estimator_reports = [
+                report
+                for report in estimator_reports
+                if not isinstance(report, Exception)
+            ]
+        elif any(isinstance(report, KeyboardInterrupt) for report in estimator_reports):
+            warn_msg = (
+                "Cross-validation process was interrupted manually before all "
+                "estimators could be fitted; CrossValidationReport object "
+                "might not contain all the expected results."
+            )
+            estimator_reports = [
+                report
+                for report in estimator_reports
+                if not isinstance(report, KeyboardInterrupt)
+            ]
 
-            if isinstance(e, KeyboardInterrupt):
-                message = (
-                    "Cross-validation process was interrupted manually before all "
-                    "estimators could be fitted; CrossValidationReport object "
-                    "might not contain all the expected results."
-                )
-            else:
-                message = (
-                    "Cross-validation process was interrupted by an error before "
-                    "all estimators could be fitted; CrossValidationReport object "
-                    "might not contain all the expected results. "
-                    f"Traceback: \n{e}"
-                )
+        if warn_msg is not None:
+            from skore import console  # avoid circular import
 
             console.print(
                 Panel(
                     title="Cross-validation interrupted",
-                    renderable=message,
+                    renderable=warn_msg,
                     style="orange1",
                     border_style="cyan",
                 )

skore/src/skore/utils/_testing.py

@@ -1,6 +1,9 @@
 import contextlib
 import copy
 
+import numpy as np
+from sklearn.base import BaseEstimator, ClassifierMixin
+
 
 @contextlib.contextmanager
 def check_cache_changed(value):
@@ -16,3 +19,23 @@ def check_cache_unchanged(value):
     initial_value = copy.copy(value)
     yield
     assert value == initial_value
+
+
+class MockEstimator(ClassifierMixin, BaseEstimator):
+    def __init__(self, *, error, n_call=0, fail_after_n_clone=3):
+        self.error = error
+        self.n_call = n_call
+        self.fail_after_n_clone = fail_after_n_clone
+
+    def fit(self, X, y):
+        if self.n_call > self.fail_after_n_clone:
+            raise self.error
+        self.classes_ = np.unique(y)
+        return self
+
+    def __sklearn_clone__(self):
+        self.n_call += 1
+        return self
+
+    def predict(self, X):
+        return np.ones(X.shape[0])

skore/tests/unit/sklearn/cross_validation/test_cross_validation.py

@@ -4,7 +4,7 @@
 import numpy as np
 import pandas as pd
 import pytest
-from sklearn.base import BaseEstimator, ClassifierMixin, clone
+from sklearn.base import clone
 from sklearn.datasets import make_classification, make_regression
 from sklearn.ensemble import RandomForestClassifier
 from sklearn.exceptions import NotFittedError
@@ -26,6 +26,7 @@
 )
 from skore.sklearn._estimator import EstimatorReport
 from skore.sklearn._plot import RocCurveDisplay
+from skore.utils._testing import MockEstimator
 
 
 @pytest.fixture
@@ -895,38 +896,16 @@ def test_cross_validation_report_custom_metric(binary_classification_data):
         (KeyboardInterrupt(), "Cross-validation interrupted manually"),
     ],
 )
+@pytest.mark.parametrize("n_jobs", [None, 1, 2])
 def test_cross_validation_report_interrupted(
-    binary_classification_data, capsys, error, error_message
+    binary_classification_data, capsys, error, error_message, n_jobs
 ):
     """Check that we can interrupt cross-validation without losing all
     data."""
-
-    class MockEstimator(ClassifierMixin, BaseEstimator):
-        def __init__(self, n_call=0, fail_after_n_clone=3):
-            self.n_call = n_call
-            self.fail_after_n_clone = fail_after_n_clone
-
-        def fit(self, X, y):
-            if self.n_call > self.fail_after_n_clone:
-                raise error
-            self.classes_ = np.unique(y)
-            return self
-
-        def __sklearn_clone__(self):
-            """Do not clone the estimator
-
-            Instead, we increment a counter each time that
-            `sklearn.clone` is called.
-            """
-            self.n_call += 1
-            return self
-
-        def predict(self, X):
-            return np.ones(X.shape[0])
-
     _, X, y = binary_classification_data
 
-    report = CrossValidationReport(MockEstimator(), X, y, cv_splitter=10)
+    estimator = MockEstimator(error=error, n_call=0, fail_after_n_clone=8)
+    report = CrossValidationReport(estimator, X, y, cv_splitter=10, n_jobs=n_jobs)
 
     captured = capsys.readouterr()
     assert all(word in captured.out for word in error_message.split(" "))
@@ -990,6 +969,20 @@ def test_cross_validation_timings(
     assert timings.columns.tolist() == expected_columns
 
 
+@pytest.mark.parametrize("n_jobs", [None, 1, 2])
+def test_cross_validation_report_failure_all_splits(n_jobs):
+    """Check that we raise an error when no estimators were successfully fitted.
+    during the cross-validation process."""
+    X, y = make_classification(n_samples=100, n_features=10, random_state=42)
+    estimator = MockEstimator(
+        error=ValueError("Intentional failure for testing"), fail_after_n_clone=0
+    )
+
+    err_msg = "Cross-validation failed: no estimators were successfully fitted"
+    with pytest.raises(RuntimeError, match=err_msg):
+        CrossValidationReport(estimator, X, y, n_jobs=n_jobs)
+
+
 def test_cross_validation_timings_flat_index(binary_classification_data):
     """Check the behaviour of the `timings` method display formatting."""
     estimator, X, y = binary_classification_data