community: If load() has been overridden, use it in default lazy_load() (#18690)

libs/core/langchain_core/document_loaders/base.py

@@ -63,6 +63,8 @@ class BaseLoader(ABC):
     #            implemented in all the existing subclasses.
     def lazy_load(self) -> Iterator[Document]:
         """A lazy loader for Documents."""
+        if type(self).load != BaseLoader.load:
+            return iter(self.load())
         raise NotImplementedError(
             f"{self.__class__.__name__} does not implement lazy_load()"
         )

libs/core/tests/unit_tests/document_loaders/test_base.py

@@ -1,11 +1,12 @@
 """Test Base Schema of documents."""
-from typing import Iterator
+from typing import Iterator, List
 
+import pytest
+
+from langchain_core.document_loaders.base import BaseBlobParser, BaseLoader
+from langchain_core.document_loaders.blob_loaders import Blob
 from langchain_core.documents import Document
 
-from langchain_community.document_loaders.base import BaseBlobParser, BaseLoader
-from langchain_community.document_loaders.blob_loaders import Blob
-
 
 def test_base_blob_parser() -> None:
     """Verify that the eager method is hooked up to the lazy method by default."""
@@ -29,6 +30,28 @@ def test_base_blob_parser() -> None:
     assert docs[0].page_content == "foo"
 
 
+def test_default_lazy_load() -> None:
+    class FakeLoader(BaseLoader):
+        def load(self) -> List[Document]:
+            return [
+                Document(page_content="foo"),
+                Document(page_content="bar"),
+            ]
+
+    loader = FakeLoader()
+    docs = list(loader.lazy_load())
+    assert docs == [Document(page_content="foo"), Document(page_content="bar")]
+
+
+def test_lazy_load_not_implemented() -> None:
+    class FakeLoader(BaseLoader):
+        pass
+
+    loader = FakeLoader()
+    with pytest.raises(NotImplementedError):
+        loader.lazy_load()
+
+
 async def test_default_aload() -> None:
     class FakeLoader(BaseLoader):
         def lazy_load(self) -> Iterator[Document]: