fix: fix serialization of DocumentRecallEvaluator (#7662)

* fix serialization of DocumentRecallEvaluator

* add requested tests

Author: anakin87

Diff for: haystack/components/evaluators/document_recall.py

@@ -1,7 +1,7 @@
 from enum import Enum
 from typing import Any, Dict, List, Union
 
-from haystack.core.component import component
+from haystack import component, default_to_dict
 from haystack.dataclasses import Document
 
 
@@ -74,6 +74,7 @@ def __init__(self, mode: Union[str, RecallMode] = RecallMode.SINGLE_HIT):
 
         mode_functions = {RecallMode.SINGLE_HIT: self._recall_single_hit, RecallMode.MULTI_HIT: self._recall_multi_hit}
         self.mode_function = mode_functions[mode]
+        self.mode = mode
 
     def _recall_single_hit(self, ground_truth_documents: List[Document], retrieved_documents: List[Document]) -> float:
         unique_truths = {g.content for g in ground_truth_documents}
@@ -117,3 +118,12 @@ def run(
             scores.append(score)
 
         return {"score": sum(scores) / len(retrieved_documents), "individual_scores": scores}
+
+    def to_dict(self) -> Dict[str, Any]:
+        """
+        Serializes the component to a dictionary.
+
+        :returns:
+            Dictionary with serialized data.
+        """
+        return default_to_dict(self, mode=str(self.mode))

Diff for: releasenotes/notes/fix-serialization-docrecallevaluator-91ad772ffed119ed.yaml

@@ -0,0 +1,4 @@
+---
+fixes:
+  - |
+    Add `to_dict` method to `DocumentRecallEvaluator` to allow proper serialization of the component.

Diff for: test/components/evaluators/test_document_recall.py

@@ -2,6 +2,7 @@
 
 from haystack.components.evaluators.document_recall import DocumentRecallEvaluator, RecallMode
 from haystack.dataclasses import Document
+from haystack import default_from_dict
 
 
 def test_init_with_unknown_mode_string():
@@ -78,6 +79,21 @@ def test_run_with_different_lengths(self, evaluator):
                 retrieved_documents=[[Document(content="Berlin")]],
             )
 
+    def test_to_dict(self, evaluator):
+        data = evaluator.to_dict()
+        assert data == {
+            "type": "haystack.components.evaluators.document_recall.DocumentRecallEvaluator",
+            "init_parameters": {"mode": "single_hit"},
+        }
+
+    def test_from_dict(self):
+        data = {
+            "type": "haystack.components.evaluators.document_recall.DocumentRecallEvaluator",
+            "init_parameters": {"mode": "single_hit"},
+        }
+        new_evaluator = default_from_dict(DocumentRecallEvaluator, data)
+        assert new_evaluator.mode == RecallMode.SINGLE_HIT
+
 
 class TestDocumentRecallEvaluatorMultiHit:
     @pytest.fixture
@@ -152,3 +168,18 @@ def test_run_with_different_lengths(self, evaluator):
                 ground_truth_documents=[[Document(content="Berlin")], [Document(content="Paris")]],
                 retrieved_documents=[[Document(content="Berlin")]],
             )
+
+    def test_to_dict(self, evaluator):
+        data = evaluator.to_dict()
+        assert data == {
+            "type": "haystack.components.evaluators.document_recall.DocumentRecallEvaluator",
+            "init_parameters": {"mode": "multi_hit"},
+        }
+
+    def test_from_dict(self):
+        data = {
+            "type": "haystack.components.evaluators.document_recall.DocumentRecallEvaluator",
+            "init_parameters": {"mode": "multi_hit"},
+        }
+        new_evaluator = default_from_dict(DocumentRecallEvaluator, data)
+        assert new_evaluator.mode == RecallMode.MULTI_HIT