feat(langchain): validate peer dependency (#308)

examples/extensions/langchain/__init__.py

@@ -6,4 +6,12 @@
 
     To use the following extension, first install it by running
     :bash:`pip install 'ibm-generative-ai[langchain]'`.
+
+
+.. admonition:: LangChain versions
+    :class: attention
+
+    Our LangChain extension depends on `langchain-core` library.
+    In case you are also using `langchain` library, please do ensure you are using version >= 0.1.0
+    to prevent possible bugs.
 """

src/genai/extensions/langchain/__init__.py

@@ -1,4 +1,9 @@
 """Extension for LangChain library"""
+import warnings
+from importlib.metadata import PackageNotFoundError
+from importlib.metadata import version as get_package_version
+
+from packaging.version import parse as parse_version
 
 from genai.extensions.langchain.chat_llm import LangChainChatInterface
 from genai.extensions.langchain.embeddings import LangChainEmbeddingsInterface
@@ -8,6 +13,27 @@
     to_langchain_template,
 )
 
+
+def _verify_langchain_version():
+    try:
+        langchain_version = get_package_version("langchain")
+        minimal_valid_version = parse_version("0.1.0")
+        current_version = parse_version(langchain_version)
+
+        if current_version < minimal_valid_version:
+            warnings.warn(
+                category=RuntimeWarning,
+                stacklevel=4,
+                message=f"You are using 'langchain' package version {current_version}. "
+                f"Please do upgrade now to version >= {minimal_valid_version}.",
+            )
+
+    except PackageNotFoundError:
+        pass
+
+
+_verify_langchain_version()
+
 __all__ = [
     "LangChainInterface",
     "LangChainChatInterface",