informative import error messages (#25)

DEVELOPMENT.md

@@ -95,3 +95,16 @@ Automated releases are handled by the [release workflow][release-workflow] which
 Testing, type checking, and formatting/linting is [checked in CI][ci].
 
 [ci]: .github/workflows/ci.yml
+
+## Style guide
+
+### Adding integrations with external libraries
+
+When adding integrations with external libraries, always use a lazy import. The external dependency should not be required to use the `cleanlab-codex` library. Wrap the lazy import in a `try`/`except` block to catch the `ImportError` and raise a `MissingDependencyError` with a helpful message. See [codex_tool.py](src/cleanlab_codex/codex_tool.py) file for examples one of which is shown below:
+
+```python
+try:
+    from cleanlab_codex.utils.smolagents import CodexTool as SmolagentsCodexTool
+except ImportError as e:
+    raise MissingDependencyError("smolagents", "https://github.com/huggingface/smolagents") from e
+```

pyproject.toml

@@ -101,4 +101,4 @@ html = "coverage html"
 xml = "coverage xml"
 
 [tool.ruff.lint]
-ignore = ["FA100", "UP007", "UP006"]
+ignore = ["FA100", "UP007", "UP006", "EM101"]

src/cleanlab_codex/codex_tool.py

@@ -7,7 +7,11 @@
 from typing_extensions import Annotated
 
 from cleanlab_codex.project import Project
-from cleanlab_codex.utils.function import pydantic_model_from_function, required_properties_from_model
+from cleanlab_codex.utils.errors import MissingDependencyError
+from cleanlab_codex.utils.function import (
+    pydantic_model_from_function,
+    required_properties_from_model,
+)
 
 
 class CodexTool:
@@ -119,7 +123,10 @@ def to_smolagents_tool(self) -> Any:
 
         Note: You must have the [`smolagents` library installed](https://github.com/huggingface/smolagents) to use this method.
         """
-        from cleanlab_codex.utils.smolagents import CodexTool as SmolagentsCodexTool
+        try:
+            from cleanlab_codex.utils.smolagents import CodexTool as SmolagentsCodexTool
+        except ImportError as e:
+            raise MissingDependencyError("smolagents", "https://github.com/huggingface/smolagents") from e
 
         return SmolagentsCodexTool(
             query=self.query,
@@ -133,7 +140,14 @@ def to_llamaindex_tool(self) -> Any:
 
         Note: You must have the [`llama-index` library installed](https://docs.llamaindex.ai/en/stable/getting_started/installation/) to use this method.
         """
-        from llama_index.core.tools import FunctionTool
+        try:
+            from llama_index.core.tools import FunctionTool
+
+        except ImportError as e:
+            raise MissingDependencyError(
+                "llama-index-core",
+                "https://docs.llamaindex.ai/en/stable/getting_started/installation/",
+            ) from e
 
         return FunctionTool.from_defaults(
             fn=self.query,
@@ -147,7 +161,11 @@ def to_langchain_tool(self) -> Any:
 
         Note: You must have the [`langchain` library installed](https://python.langchain.com/docs/concepts/architecture/) to use this method.
         """
-        from langchain_core.tools.structured import StructuredTool
+        try:
+            from langchain_core.tools.structured import StructuredTool
+
+        except ImportError as e:
+            raise MissingDependencyError("langchain", "https://pypi.org/project/langchain/") from e
 
         return StructuredTool.from_function(
             func=self.query,

src/cleanlab_codex/utils/errors.py

@@ -0,0 +1,15 @@
+from __future__ import annotations
+
+
+class MissingDependencyError(Exception):
+    """Raised when a lazy import is missing."""
+
+    def __init__(self, import_name: str, package_url: str | None = None) -> None:
+        self.import_name = import_name
+        self.package_url = package_url
+
+    def __str__(self) -> str:
+        message = f"Failed to import {self.import_name}. Please install the package using `pip install {self.import_name}` and try again."
+        if self.package_url:
+            message += f" For more information, see {self.package_url}."
+        return message