Langchain has an __init__.py with the following content

# ruff: noqa: E402
import pytest

# Rewrite assert statements for test suite so that implementations can
# see the full error message from failed asserts.
# https://docs.pytest.org/en/7.1.x/how-to/writing_plugins.html#assertion-rewriting
modules = [
    "chat_models",
    "embeddings",
    "tools",
]

for module in modules:
    pytest.register_assert_rewrite(f"langchain_tests.unit_tests.{module}")

from .chat_models import ChatModelUnitTests
from .embeddings import EmbeddingsUnitTests
from .tools import ToolsUnitTests

__all__ = ["ChatModelUnitTests", "EmbeddingsUnitTests", "ToolsUnitTests"]

ty fails to resolve the relative imports chat_models, embeddings and .tools even though those files clearly exist. Pyright seems fine with the import.

The issue seems to be that file_to_module fails because the relative path to the search root (which is the project root) libs/standard-tests/langchain_tests/unit_tests/teswt.py can't be turned into a valid module name because of the standard-tests.

A solution here is to add standard-tests to the search path but having to do this is at least confusing in an LSP setup (where ty should just work out of the box)

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