core[patch]: Raise AttributeError (instead of ModuleNotFoundError) in custom __getattr__ (#30905)

Follow up to https://github.com/langchain-ai/langchain/pull/30769,
fixing the regression reported
[here](https://github.com/langchain-ai/langchain/pull/30769#issuecomment-2807483610),
thanks @krassowski for the report!

Fix inspired by https://github.com/PrefectHQ/prefect/pull/16172/files

Other changes:
* Using tuples for `__all__`, except in `output_parsers` bc of a list
namespace conflict
* Using a helper function for imports due to repeated logic across
`__init__.py` files becoming hard to maintain.

Co-authored-by: Michał Krassowski < krassowski 5832902+krassowski@users.noreply.github.com>"

libs/core/langchain_core/_api/__init__.py

@@ -9,9 +9,10 @@ This module is only relevant for LangChain developers, not for users.
 
 """
 
-from importlib import import_module
 from typing import TYPE_CHECKING
 
+from langchain_core._import_utils import import_attr
+
 if TYPE_CHECKING:
     from .beta_decorator import (
         LangChainBetaWarning,
@@ -28,7 +29,7 @@ if TYPE_CHECKING:
     )
     from .path import as_import_path, get_relative_path
 
-__all__ = [
+__all__ = (
     "as_import_path",
     "beta",
     "deprecated",
@@ -40,7 +41,7 @@ __all__ = [
     "suppress_langchain_deprecation_warning",
     "surface_langchain_deprecation_warnings",
     "warn_deprecated",
-]
+)
 
 _dynamic_imports = {
     "LangChainBetaWarning": "beta_decorator",
@@ -59,12 +60,7 @@ _dynamic_imports = {
 
 def __getattr__(attr_name: str) -> object:
     module_name = _dynamic_imports.get(attr_name)
-    package = __spec__.parent
-    if module_name == "__module__" or module_name is None:
-        result = import_module(f".{attr_name}", package=package)
-    else:
-        module = import_module(f".{module_name}", package=package)
-        result = getattr(module, attr_name)
+    result = import_attr(attr_name, module_name, __spec__.parent)
     globals()[attr_name] = result
     return result
 

libs/core/langchain_core/_import_utils.py

@@ -0,0 +1,34 @@
+from importlib import import_module
+from typing import Union
+
+
+def import_attr(
+    attr_name: str,
+    module_name: Union[str, None],
+    package: Union[str, None],
+) -> object:
+    """Import an attribute from a module located in a package.
+
+    This utility function is used in custom __getattr__ methods within __init__.py
+    files to dynamically import attributes.
+
+    Args:
+        attr_name: The name of the attribute to import.
+        module_name: The name of the module to import from. If None, the attribute
+            is imported from the package itself.
+        package: The name of the package where the module is located.
+    """
+    if module_name == "__module__" or module_name is None:
+        try:
+            result = import_module(f".{attr_name}", package=package)
+        except ModuleNotFoundError:
+            msg = f"module '{package!r}' has no attribute {attr_name!r}"
+            raise AttributeError(msg) from None
+    else:
+        try:
+            module = import_module(f".{module_name}", package=package)
+        except ModuleNotFoundError:
+            msg = f"module '{package!r}.{module_name!r}' not found"
+            raise ImportError(msg) from None
+        result = getattr(module, attr_name)
+    return result

libs/core/langchain_core/callbacks/__init__.py

@@ -7,9 +7,10 @@
     BaseCallbackHandler --> <name>CallbackHandler  # Example: AimCallbackHandler
 """
 
-from importlib import import_module
 from typing import TYPE_CHECKING
 
+from langchain_core._import_utils import import_attr
+
 if TYPE_CHECKING:
     from langchain_core.callbacks.base import (
         AsyncCallbackHandler,
@@ -52,7 +53,7 @@ if TYPE_CHECKING:
         get_usage_metadata_callback,
     )
 
-__all__ = [
+__all__ = (
     "dispatch_custom_event",
     "adispatch_custom_event",
     "RetrieverManagerMixin",
@@ -87,7 +88,7 @@ __all__ = [
     "FileCallbackHandler",
     "UsageMetadataCallbackHandler",
     "get_usage_metadata_callback",
-]
+)
 
 _dynamic_imports = {
     "AsyncCallbackHandler": "base",
@@ -129,12 +130,7 @@ _dynamic_imports = {
 
 def __getattr__(attr_name: str) -> object:
     module_name = _dynamic_imports.get(attr_name)
-    package = __spec__.parent
-    if module_name == "__module__" or module_name is None:
-        result = import_module(f".{attr_name}", package=package)
-    else:
-        module = import_module(f".{module_name}", package=package)
-        result = getattr(module, attr_name)
+    result = import_attr(attr_name, module_name, __spec__.parent)
     globals()[attr_name] = result
     return result
 

libs/core/langchain_core/document_loaders/__init__.py

@@ -1,21 +1,22 @@
 """Document loaders."""
 
-from importlib import import_module
 from typing import TYPE_CHECKING
 
+from langchain_core._import_utils import import_attr
+
 if TYPE_CHECKING:
     from langchain_core.document_loaders.base import BaseBlobParser, BaseLoader
     from langchain_core.document_loaders.blob_loaders import Blob, BlobLoader, PathLike
     from langchain_core.document_loaders.langsmith import LangSmithLoader
 
-__all__ = [
+__all__ = (
     "BaseBlobParser",
     "BaseLoader",
     "Blob",
     "BlobLoader",
     "PathLike",
     "LangSmithLoader",
-]
+)
 
 _dynamic_imports = {
     "BaseBlobParser": "base",
@@ -29,12 +30,7 @@ _dynamic_imports = {
 
 def __getattr__(attr_name: str) -> object:
     module_name = _dynamic_imports.get(attr_name)
-    package = __spec__.parent
-    if module_name == "__module__" or module_name is None:
-        result = import_module(f".{attr_name}", package=package)
-    else:
-        module = import_module(f".{module_name}", package=package)
-        result = getattr(module, attr_name)
+    result = import_attr(attr_name, module_name, __spec__.parent)
     globals()[attr_name] = result
     return result
 

libs/core/langchain_core/documents/__init__.py

@@ -5,15 +5,16 @@ and their transformations.
 
 """
 
-from importlib import import_module
 from typing import TYPE_CHECKING
 
+from langchain_core._import_utils import import_attr
+
 if TYPE_CHECKING:
     from .base import Document
     from .compressor import BaseDocumentCompressor
     from .transformers import BaseDocumentTransformer
 
-__all__ = ["Document", "BaseDocumentTransformer", "BaseDocumentCompressor"]
+__all__ = ("Document", "BaseDocumentTransformer", "BaseDocumentCompressor")
 
 _dynamic_imports = {
     "Document": "base",
@@ -24,12 +25,7 @@ _dynamic_imports = {
 
 def __getattr__(attr_name: str) -> object:
     module_name = _dynamic_imports.get(attr_name)
-    package = __spec__.parent
-    if module_name == "__module__" or module_name is None:
-        result = import_module(f".{attr_name}", package=package)
-    else:
-        module = import_module(f".{module_name}", package=package)
-        result = getattr(module, attr_name)
+    result = import_attr(attr_name, module_name, __spec__.parent)
     globals()[attr_name] = result
     return result
 

libs/core/langchain_core/embeddings/__init__.py

@@ -1,8 +1,9 @@
 """Embeddings."""
 
-from importlib import import_module
 from typing import TYPE_CHECKING
 
+from langchain_core._import_utils import import_attr
+
 if TYPE_CHECKING:
     from langchain_core.embeddings.embeddings import Embeddings
     from langchain_core.embeddings.fake import (
@@ -10,7 +11,7 @@ if TYPE_CHECKING:
         FakeEmbeddings,
     )
 
-__all__ = ["DeterministicFakeEmbedding", "Embeddings", "FakeEmbeddings"]
+__all__ = ("DeterministicFakeEmbedding", "Embeddings", "FakeEmbeddings")
 
 _dynamic_imports = {
     "Embeddings": "embeddings",
@@ -21,12 +22,7 @@ _dynamic_imports = {
 
 def __getattr__(attr_name: str) -> object:
     module_name = _dynamic_imports.get(attr_name)
-    package = __spec__.parent
-    if module_name == "__module__" or module_name is None:
-        result = import_module(f".{attr_name}", package=package)
-    else:
-        module = import_module(f".{module_name}", package=package)
-        result = getattr(module, attr_name)
+    result = import_attr(attr_name, module_name, __spec__.parent)
     globals()[attr_name] = result
     return result
 

libs/core/langchain_core/example_selectors/__init__.py

@@ -4,9 +4,10 @@
 This allows us to select examples that are most relevant to the input.
 """
 
-from importlib import import_module
 from typing import TYPE_CHECKING
 
+from langchain_core._import_utils import import_attr
+
 if TYPE_CHECKING:
     from langchain_core.example_selectors.base import BaseExampleSelector
     from langchain_core.example_selectors.length_based import (
@@ -18,13 +19,13 @@ if TYPE_CHECKING:
         sorted_values,
     )
 
-__all__ = [
+__all__ = (
     "BaseExampleSelector",
     "LengthBasedExampleSelector",
     "MaxMarginalRelevanceExampleSelector",
     "SemanticSimilarityExampleSelector",
     "sorted_values",
-]
+)
 
 _dynamic_imports = {
     "BaseExampleSelector": "base",
@@ -37,12 +38,7 @@ _dynamic_imports = {
 
 def __getattr__(attr_name: str) -> object:
     module_name = _dynamic_imports.get(attr_name)
-    package = __spec__.parent
-    if module_name == "__module__" or module_name is None:
-        result = import_module(f".{attr_name}", package=package)
-    else:
-        module = import_module(f".{module_name}", package=package)
-        result = getattr(module, attr_name)
+    result = import_attr(attr_name, module_name, __spec__.parent)
     globals()[attr_name] = result
     return result
 

libs/core/langchain_core/indexing/__init__.py

@@ -5,9 +5,10 @@ a vectorstore while avoiding duplicated content and over-writing content
 if it's unchanged.
 """
 
-from importlib import import_module
 from typing import TYPE_CHECKING
 
+from langchain_core._import_utils import import_attr
+
 if TYPE_CHECKING:
     from langchain_core.indexing.api import IndexingResult, aindex, index
     from langchain_core.indexing.base import (
@@ -18,7 +19,7 @@ if TYPE_CHECKING:
         UpsertResponse,
     )
 
-__all__ = [
+__all__ = (
     "aindex",
     "DeleteResponse",
     "DocumentIndex",
@@ -27,7 +28,7 @@ __all__ = [
     "InMemoryRecordManager",
     "RecordManager",
     "UpsertResponse",
-]
+)
 
 _dynamic_imports = {
     "aindex": "api",
@@ -43,12 +44,7 @@ _dynamic_imports = {
 
 def __getattr__(attr_name: str) -> object:
     module_name = _dynamic_imports.get(attr_name)
-    package = __spec__.parent
-    if module_name == "__module__" or module_name is None:
-        result = import_module(f".{attr_name}", package=package)
-    else:
-        module = import_module(f".{module_name}", package=package)
-        result = getattr(module, attr_name)
+    result = import_attr(attr_name, module_name, __spec__.parent)
     globals()[attr_name] = result
     return result
 

libs/core/langchain_core/language_models/__init__.py

@@ -41,9 +41,10 @@ https://python.langchain.com/docs/how_to/custom_llm/
 
 """  # noqa: E501
 
-from importlib import import_module
 from typing import TYPE_CHECKING
 
+from langchain_core._import_utils import import_attr
+
 if TYPE_CHECKING:
     from langchain_core.language_models.base import (
         BaseLanguageModel,
@@ -66,7 +67,7 @@ if TYPE_CHECKING:
     )
     from langchain_core.language_models.llms import LLM, BaseLLM
 
-__all__ = [
+__all__ = (
     "BaseLanguageModel",
     "BaseChatModel",
     "SimpleChatModel",
@@ -83,7 +84,7 @@ __all__ = [
     "FakeMessagesListChatModel",
     "GenericFakeChatModel",
     "ParrotFakeChatModel",
-]
+)
 
 _dynamic_imports = {
     "BaseLanguageModel": "base",
@@ -107,12 +108,7 @@ _dynamic_imports = {
 
 def __getattr__(attr_name: str) -> object:
     module_name = _dynamic_imports.get(attr_name)
-    package = __spec__.parent
-    if module_name == "__module__" or module_name is None:
-        result = import_module(f".{attr_name}", package=package)
-    else:
-        module = import_module(f".{module_name}", package=package)
-        result = getattr(module, attr_name)
+    result = import_attr(attr_name, module_name, __spec__.parent)
     globals()[attr_name] = result
     return result
 

libs/core/langchain_core/load/__init__.py

@@ -1,8 +1,9 @@
 """**Load** module helps with serialization and deserialization."""
 
-from importlib import import_module
 from typing import TYPE_CHECKING
 
+from langchain_core._import_utils import import_attr
+
 if TYPE_CHECKING:
     from langchain_core.load.dump import dumpd, dumps
     from langchain_core.load.load import loads
@@ -14,7 +15,7 @@ if TYPE_CHECKING:
 # the `from langchain_core.load.load import load` absolute import should also work.
 from langchain_core.load.load import load
 
-__all__ = ["dumpd", "dumps", "load", "loads", "Serializable"]
+__all__ = ("dumpd", "dumps", "load", "loads", "Serializable")
 
 _dynamic_imports = {
     "dumpd": "dump",
@@ -26,12 +27,7 @@ _dynamic_imports = {
 
 def __getattr__(attr_name: str) -> object:
     module_name = _dynamic_imports.get(attr_name)
-    package = __spec__.parent
-    if module_name == "__module__" or module_name is None:
-        result = import_module(f".{attr_name}", package=package)
-    else:
-        module = import_module(f".{module_name}", package=package)
-        result = getattr(module, attr_name)
+    result = import_attr(attr_name, module_name, __spec__.parent)
     globals()[attr_name] = result
     return result
 

libs/core/langchain_core/messages/__init__.py

@@ -15,9 +15,10 @@
 
 """  # noqa: E501
 
-from importlib import import_module
 from typing import TYPE_CHECKING
 
+from langchain_core._import_utils import import_attr
+
 if TYPE_CHECKING:
     from langchain_core.messages.ai import (
         AIMessage,
@@ -60,7 +61,7 @@ if TYPE_CHECKING:
         trim_messages,
     )
 
-__all__ = [
+__all__ = (
     "AIMessage",
     "AIMessageChunk",
     "AnyMessage",
@@ -95,7 +96,7 @@ __all__ = [
     "merge_message_runs",
     "trim_messages",
     "convert_to_openai_messages",
-]
+)
 
 _dynamic_imports = {
     "AIMessage": "ai",
@@ -137,12 +138,7 @@ _dynamic_imports = {
 
 def __getattr__(attr_name: str) -> object:
     module_name = _dynamic_imports.get(attr_name)
-    package = __spec__.parent
-    if module_name == "__module__" or module_name is None:
-        result = import_module(f".{attr_name}", package=package)
-    else:
-        module = import_module(f".{module_name}", package=package)
-        result = getattr(module, attr_name)
+    result = import_attr(attr_name, module_name, __spec__.parent)
     globals()[attr_name] = result
     return result
 

libs/core/langchain_core/output_parsers/__init__.py

@@ -13,9 +13,10 @@
     Serializable, Generation, PromptValue
 """  # noqa: E501
 
-from importlib import import_module
 from typing import TYPE_CHECKING
 
+from langchain_core._import_utils import import_attr
+
 if TYPE_CHECKING:
     from langchain_core.output_parsers.base import (
         BaseGenerationOutputParser,
@@ -88,12 +89,7 @@ _dynamic_imports = {
 
 def __getattr__(attr_name: str) -> object:
     module_name = _dynamic_imports.get(attr_name)
-    package = __spec__.parent
-    if module_name == "__module__" or module_name is None:
-        result = import_module(f".{attr_name}", package=package)
-    else:
-        module = import_module(f".{module_name}", package=package)
-        result = getattr(module, attr_name)
+    result = import_attr(attr_name, module_name, __spec__.parent)
     globals()[attr_name] = result
     return result
 

libs/core/langchain_core/outputs/__init__.py

@@ -21,9 +21,10 @@ in the AIMessage object, it is recommended to access it from there rather than
 from the `LLMResult` object.
 """
 
-from importlib import import_module
 from typing import TYPE_CHECKING
 
+from langchain_core._import_utils import import_attr
+
 if TYPE_CHECKING:
     from langchain_core.outputs.chat_generation import (
         ChatGeneration,
@@ -34,7 +35,7 @@ if TYPE_CHECKING:
     from langchain_core.outputs.llm_result import LLMResult
     from langchain_core.outputs.run_info import RunInfo
 
-__all__ = [
+__all__ = (
     "ChatGeneration",
     "ChatGenerationChunk",
     "ChatResult",
@@ -42,7 +43,7 @@ __all__ = [
     "GenerationChunk",
     "LLMResult",
     "RunInfo",
-]
+)
 
 _dynamic_imports = {
     "ChatGeneration": "chat_generation",
@@ -57,12 +58,7 @@ _dynamic_imports = {
 
 def __getattr__(attr_name: str) -> object:
     module_name = _dynamic_imports.get(attr_name)
-    package = __spec__.parent
-    if module_name == "__module__" or module_name is None:
-        result = import_module(f".{attr_name}", package=package)
-    else:
-        module = import_module(f".{module_name}", package=package)
-        result = getattr(module, attr_name)
+    result = import_attr(attr_name, module_name, __spec__.parent)
     globals()[attr_name] = result
     return result
 

libs/core/langchain_core/prompts/__init__.py

@@ -25,9 +25,10 @@ from multiple components and prompt values. Prompt classes and functions make co
 
 """  # noqa: E501
 
-from importlib import import_module
 from typing import TYPE_CHECKING
 
+from langchain_core._import_utils import import_attr
+
 if TYPE_CHECKING:
     from langchain_core.prompts.base import (
         BasePromptTemplate,
@@ -61,7 +62,7 @@ if TYPE_CHECKING:
         validate_jinja2,
     )
 
-__all__ = [
+__all__ = (
     "AIMessagePromptTemplate",
     "BaseChatPromptTemplate",
     "BasePromptTemplate",
@@ -83,7 +84,7 @@ __all__ = [
     "get_template_variables",
     "jinja2_formatter",
     "validate_jinja2",
-]
+)
 
 _dynamic_imports = {
     "BasePromptTemplate": "base",
@@ -112,12 +113,7 @@ _dynamic_imports = {
 
 def __getattr__(attr_name: str) -> object:
     module_name = _dynamic_imports.get(attr_name)
-    package = __spec__.parent
-    if module_name == "__module__" or module_name is None:
-        result = import_module(f".{attr_name}", package=package)
-    else:
-        module = import_module(f".{module_name}", package=package)
-        result = getattr(module, attr_name)
+    result = import_attr(attr_name, module_name, __spec__.parent)
     globals()[attr_name] = result
     return result
 

libs/core/langchain_core/runnables/__init__.py

@@ -17,9 +17,10 @@ creating more responsive UX.
 This module contains schema and implementation of LangChain Runnables primitives.
 """
 
-from importlib import import_module
 from typing import TYPE_CHECKING
 
+from langchain_core._import_utils import import_attr
+
 if TYPE_CHECKING:
     from langchain_core.runnables.base import (
         Runnable,
@@ -58,7 +59,7 @@ if TYPE_CHECKING:
         add,
     )
 
-__all__ = [
+__all__ = (
     "chain",
     "AddableDict",
     "ConfigurableField",
@@ -88,7 +89,7 @@ __all__ = [
     "get_config_list",
     "aadd",
     "add",
-]
+)
 
 _dynamic_imports = {
     "chain": "base",
@@ -125,12 +126,7 @@ _dynamic_imports = {
 
 def __getattr__(attr_name: str) -> object:
     module_name = _dynamic_imports.get(attr_name)
-    package = __spec__.parent
-    if module_name == "__module__" or module_name is None:
-        result = import_module(f".{attr_name}", package=package)
-    else:
-        module = import_module(f".{module_name}", package=package)
-        result = getattr(module, attr_name)
+    result = import_attr(attr_name, module_name, __spec__.parent)
     globals()[attr_name] = result
     return result
 

libs/core/langchain_core/tools/__init__.py

@@ -19,9 +19,10 @@ tool for the job.
 
 from __future__ import annotations
 
-from importlib import import_module
 from typing import TYPE_CHECKING
 
+from langchain_core._import_utils import import_attr
+
 if TYPE_CHECKING:
     from langchain_core.tools.base import (
         FILTERED_ARGS,
@@ -51,7 +52,7 @@ if TYPE_CHECKING:
     from langchain_core.tools.simple import Tool
     from langchain_core.tools.structured import StructuredTool
 
-__all__ = [
+__all__ = (
     "ArgsSchema",
     "BaseTool",
     "BaseToolkit",
@@ -71,7 +72,7 @@ __all__ = [
     "create_retriever_tool",
     "Tool",
     "StructuredTool",
-]
+)
 
 _dynamic_imports = {
     "FILTERED_ARGS": "base",
@@ -98,12 +99,7 @@ _dynamic_imports = {
 
 def __getattr__(attr_name: str) -> object:
     module_name = _dynamic_imports.get(attr_name)
-    package = __spec__.parent
-    if module_name == "__module__" or module_name is None:
-        result = import_module(f".{attr_name}", package=package)
-    else:
-        module = import_module(f".{module_name}", package=package)
-        result = getattr(module, attr_name)
+    result = import_attr(attr_name, module_name, __spec__.parent)
     globals()[attr_name] = result
     return result
 

libs/core/langchain_core/tracers/__init__.py

@@ -8,9 +8,10 @@
                                        --> <name>  # Examples: LogStreamCallbackHandler
 """  # noqa: E501
 
-from importlib import import_module
 from typing import TYPE_CHECKING
 
+from langchain_core._import_utils import import_attr
+
 if TYPE_CHECKING:
     from langchain_core.tracers.base import BaseTracer
     from langchain_core.tracers.evaluation import EvaluatorCallbackHandler
@@ -23,7 +24,7 @@ if TYPE_CHECKING:
     from langchain_core.tracers.schemas import Run
     from langchain_core.tracers.stdout import ConsoleCallbackHandler
 
-__all__ = [
+__all__ = (
     "BaseTracer",
     "EvaluatorCallbackHandler",
     "LangChainTracer",
@@ -32,7 +33,7 @@ __all__ = [
     "RunLog",
     "RunLogPatch",
     "LogStreamCallbackHandler",
-]
+)
 
 _dynamic_imports = {
     "BaseTracer": "base",
@@ -48,12 +49,7 @@ _dynamic_imports = {
 
 def __getattr__(attr_name: str) -> object:
     module_name = _dynamic_imports.get(attr_name)
-    package = __spec__.parent
-    if module_name == "__module__" or module_name is None:
-        result = import_module(f".{attr_name}", package=package)
-    else:
-        module = import_module(f".{module_name}", package=package)
-        result = getattr(module, attr_name)
+    result = import_attr(attr_name, module_name, __spec__.parent)
     globals()[attr_name] = result
     return result
 

libs/core/langchain_core/utils/__init__.py

@@ -3,9 +3,10 @@
 These functions do not depend on any other LangChain module.
 """
 
-from importlib import import_module
 from typing import TYPE_CHECKING
 
+from langchain_core._import_utils import import_attr
+
 if TYPE_CHECKING:
     # for type checking and IDE support, we include the imports here
     # but we don't want to eagerly import them at runtime
@@ -36,7 +37,7 @@ if TYPE_CHECKING:
         xor_args,
     )
 
-__all__ = [
+__all__ = (
     "build_extra_kwargs",
     "StrictFormatter",
     "check_package_version",
@@ -63,7 +64,7 @@ __all__ = [
     "abatch_iterate",
     "from_env",
     "secret_from_env",
-]
+)
 
 _dynamic_imports = {
     "image": "__module__",
@@ -97,12 +98,7 @@ _dynamic_imports = {
 
 def __getattr__(attr_name: str) -> object:
     module_name = _dynamic_imports.get(attr_name)
-    package = __spec__.parent
-    if module_name == "__module__" or module_name is None:
-        result = import_module(f".{attr_name}", package=package)
-    else:
-        module = import_module(f".{module_name}", package=package)
-        result = getattr(module, attr_name)
+    result = import_attr(attr_name, module_name, __spec__.parent)
     globals()[attr_name] = result
     return result
 

libs/core/langchain_core/vectorstores/__init__.py

@@ -1,11 +1,34 @@
 """Vector stores."""
 
-from langchain_core.vectorstores.base import VST, VectorStore, VectorStoreRetriever
-from langchain_core.vectorstores.in_memory import InMemoryVectorStore
+from typing import TYPE_CHECKING
 
-__all__ = [
+from langchain_core._import_utils import import_attr
+
+if TYPE_CHECKING:
+    from langchain_core.vectorstores.base import VST, VectorStore, VectorStoreRetriever
+    from langchain_core.vectorstores.in_memory import InMemoryVectorStore
+
+__all__ = (
     "VectorStore",
     "VST",
     "VectorStoreRetriever",
     "InMemoryVectorStore",
-]
+)
+
+_dynamic_imports = {
+    "VectorStore": "base",
+    "VST": "base",
+    "VectorStoreRetriever": "base",
+    "InMemoryVectorStore": "in_memory",
+}
+
+
+def __getattr__(attr_name: str) -> object:
+    module_name = _dynamic_imports.get(attr_name)
+    result = import_attr(attr_name, module_name, __spec__.parent)
+    globals()[attr_name] = result
+    return result
+
+
+def __dir__() -> list[str]:
+    return list(__all__)

libs/core/tests/unit_tests/indexing/test_public_api.py

@@ -3,7 +3,7 @@ from langchain_core.indexing import __all__
 
 def test_all() -> None:
     """Use to catch obvious breaking changes."""
-    assert __all__ == sorted(__all__, key=str.lower)
+    assert list(__all__) == sorted(__all__, key=str.lower)
     assert set(__all__) == {
         "aindex",
         "DeleteResponse",