fix(langchain): add test to verify version (#34644)

verify version in langchain to avoid accidental drift

libs/langchain_v1/langchain/__init__.py

@@ -1,3 +1,3 @@
 """Main entrypoint into LangChain."""
 
-__version__ = "1.2.0"
+__version__ = "1.2.2"

libs/langchain_v1/tests/unit_tests/test_version.py

@@ -0,0 +1,27 @@
+"""Test that package version is consistent across configuration files."""
+
+from pathlib import Path
+
+import toml
+
+import langchain
+
+
+def test_version_matches_pyproject() -> None:
+    """Verify that __version__ in __init__.py matches version in pyproject.toml."""
+    # Get the version from the package __init__.py
+    init_version = langchain.__version__
+
+    # Read the version from pyproject.toml
+    pyproject_path = Path(__file__).parent.parent.parent / "pyproject.toml"
+    with pyproject_path.open() as f:
+        pyproject_data = toml.load(f)
+
+    pyproject_version = pyproject_data["project"]["version"]
+
+    # Assert they match
+    assert init_version == pyproject_version, (
+        f"Version mismatch: __init__.py has '{init_version}' but "
+        f"pyproject.toml has '{pyproject_version}'. "
+        f"Please update langchain/__init__.py to match pyproject.toml."
+    )