fix some metadata routing

molpipeline/pipeline/_skl_pipeline.py

@@ -2,6 +2,7 @@
 
 from __future__ import annotations
 
+from copy import deepcopy
 from typing import Any, Iterable, List, Literal, Optional, Tuple, TypeVar, Union
 
 try:
@@ -18,10 +19,13 @@
 from sklearn.pipeline import Pipeline as _Pipeline
 from sklearn.pipeline import _final_estimator_has, _fit_transform_one
 from sklearn.utils import Bunch
+from sklearn.utils._tags import get_tags, Tags  # pylint: disable=protected-access
 from sklearn.utils.metadata_routing import (
     _routing_enabled,  # pylint: disable=protected-access
 )
 from sklearn.utils.metadata_routing import (
+    MetadataRouter,
+    MethodMapping,
     process_routing,
 )
 from sklearn.utils.metaestimators import available_if
@@ -482,7 +486,9 @@ def fit(self, X: Any, y: Any = None, **fit_params: Any) -> Self:
                         "All input rows were filtered out! Model is not fitted!"
                     )
                 else:
-                    fit_params_last_step = routed_params[self.steps[-1][0]]
+                    fit_params_last_step = routed_params[
+                        self._non_post_processing_steps()[-1][0]
+                    ]
                     self._final_estimator.fit(Xt, yt, **fit_params_last_step["fit"])
 
         return self
@@ -552,7 +558,9 @@ def fit_transform(self, X: Any, y: Any = None, **params: Any) -> Any:
             elif is_empty(iter_input):
                 logger.warning("All input rows were filtered out! Model is not fitted!")
             else:
-                last_step_params = routed_params[self.steps[-1][0]]
+                last_step_params = routed_params[
+                    self._non_post_processing_steps()[-1][0]
+                ]
                 if hasattr(last_step, "fit_transform"):
                     iter_input = last_step.fit_transform(
                         iter_input, iter_label, **last_step_params["fit_transform"]
@@ -615,7 +623,8 @@ def predict(self, X: Any, **params: Any) -> Any:
         elif hasattr(self._final_estimator, "predict"):
             if _routing_enabled():
                 iter_input = self._final_estimator.predict(
-                    iter_input, **routed_params[self._final_estimator].predict
+                    iter_input,
+                    **routed_params[self._non_post_processing_steps()[-1][0]].predict,
                 )
             else:
                 iter_input = self._final_estimator.predict(iter_input, **params)
@@ -665,7 +674,7 @@ def fit_predict(self, X: Any, y: Any = None, **params: Any) -> Any:
             X, y, routed_params
         )  # pylint: disable=invalid-name
 
-        params_last_step = routed_params[self.steps[-1][0]]
+        params_last_step = routed_params[self._non_post_processing_steps()[-1][0]]
         with print_elapsed_time("Pipeline", self._log_message(len(self.steps) - 1)):
             if self._final_estimator == "passthrough":
                 y_pred = iter_input
@@ -724,7 +733,10 @@ def predict_proba(self, X: Any, **params: Any) -> Any:
         elif hasattr(self._final_estimator, "predict_proba"):
             if _routing_enabled():
                 iter_input = self._final_estimator.predict_proba(
-                    iter_input, **routed_params[self.steps[-1][0]].predict_proba
+                    iter_input,
+                    **routed_params[
+                        self._non_post_processing_steps()[-1][0]
+                    ].predict_proba,
                 )
             else:
                 iter_input = self._final_estimator.predict_proba(iter_input, **params)
@@ -854,3 +866,123 @@ def classes_(self) -> list[Any] | npt.NDArray[Any]:
         if hasattr(last_step, "classes_"):
             return last_step.classes_
         raise ValueError("Last step has no classes_ attribute.")
+
+    def __sklearn_tags__(self) -> Tags:
+        """Return the sklearn tags."""
+        tags = super().__sklearn_tags__()
+
+        if not self.steps:
+            return tags
+
+        try:
+            if self.steps[0][1] is not None and self.steps[0][1] != "passthrough":
+                tags.input_tags.pairwise = get_tags(
+                    self.steps[0][1]
+                ).input_tags.pairwise
+            # WARNING: the sparse tag can be incorrect.
+            # Some Pipelines accepting sparse data are wrongly tagged sparse=False.
+            # For example Pipeline([PCA(), estimator]) accepts sparse data
+            # even if the estimator doesn't as PCA outputs a dense array.
+            tags.input_tags.sparse = all(
+                get_tags(step).input_tags.sparse
+                for name, step in self.steps
+                if step != "passthrough"
+            )
+        except (ValueError, AttributeError, TypeError):
+            # This happens when the `steps` is not a list of (name, estimator)
+            # tuples and `fit` is not called yet to validate the steps.
+            pass
+
+        try:
+            # Only the _final_estimator is changed from the original implementation
+            if (
+                self._final_estimator is not None
+                and self._final_estimator != "passthrough"
+            ):
+                last_step_tags = get_tags(self._final_estimator)
+                tags.estimator_type = last_step_tags.estimator_type
+                tags.target_tags.multi_output = last_step_tags.target_tags.multi_output
+                tags.classifier_tags = deepcopy(last_step_tags.classifier_tags)
+                tags.regressor_tags = deepcopy(last_step_tags.regressor_tags)
+                tags.transformer_tags = deepcopy(last_step_tags.transformer_tags)
+        except (ValueError, AttributeError, TypeError):
+            # This happens when the `steps` is not a list of (name, estimator)
+            # tuples and `fit` is not called yet to validate the steps.
+            pass
+
+        return tags
+
+    def get_metadata_routing(self) -> MetadataRouter:
+        """Get metadata routing of this object.
+
+        Please check :ref:`User Guide <metadata_routing>` on how the routing
+        mechanism works.
+
+        Returns
+        -------
+        MetadataRouter
+            A :class:`~sklearn.utils.metadata_routing.MetadataRouter` encapsulating
+            routing information.
+        """
+        router = MetadataRouter(owner=self.__class__.__name__)
+
+        # first we add all steps except the last one
+        for _, name, trans in self._iter(with_final=False, filter_passthrough=True):
+            method_mapping = MethodMapping()
+            # fit, fit_predict, and fit_transform call fit_transform if it
+            # exists, or else fit and transform
+            if hasattr(trans, "fit_transform"):
+                (
+                    method_mapping.add(caller="fit", callee="fit_transform")
+                    .add(caller="fit_transform", callee="fit_transform")
+                    .add(caller="fit_predict", callee="fit_transform")
+                )
+            else:
+                (
+                    method_mapping.add(caller="fit", callee="fit")
+                    .add(caller="fit", callee="transform")
+                    .add(caller="fit_transform", callee="fit")
+                    .add(caller="fit_transform", callee="transform")
+                    .add(caller="fit_predict", callee="fit")
+                    .add(caller="fit_predict", callee="transform")
+                )
+
+            (
+                method_mapping.add(caller="predict", callee="transform")
+                .add(caller="predict", callee="transform")
+                .add(caller="predict_proba", callee="transform")
+                .add(caller="decision_function", callee="transform")
+                .add(caller="predict_log_proba", callee="transform")
+                .add(caller="transform", callee="transform")
+                .add(caller="inverse_transform", callee="inverse_transform")
+                .add(caller="score", callee="transform")
+            )
+
+            router.add(method_mapping=method_mapping, **{name: trans})
+
+        final_name, final_est = self._non_post_processing_steps()[-1]
+        if final_est is None or final_est == "passthrough":
+            return router
+
+        # then we add the last step
+        method_mapping = MethodMapping()
+        if hasattr(final_est, "fit_transform"):
+            method_mapping.add(caller="fit_transform", callee="fit_transform")
+        else:
+            method_mapping.add(caller="fit", callee="fit").add(
+                caller="fit", callee="transform"
+            )
+        (
+            method_mapping.add(caller="fit", callee="fit")
+            .add(caller="predict", callee="predict")
+            .add(caller="fit_predict", callee="fit_predict")
+            .add(caller="predict_proba", callee="predict_proba")
+            .add(caller="decision_function", callee="decision_function")
+            .add(caller="predict_log_proba", callee="predict_log_proba")
+            .add(caller="transform", callee="transform")
+            .add(caller="inverse_transform", callee="inverse_transform")
+            .add(caller="score", callee="score")
+        )
+
+        router.add(method_mapping=method_mapping, **{final_name: final_est})
+        return router