fix: created custom error when env var for providers does not exist or unknown provider, moderator is attempted to be loaded

src/exchange/load_exchange_attribute_error.py

@@ -0,0 +1,13 @@
+from typing import List
+
+
+class LoadExchangeAttributeError(Exception):
+    def __init__(self, attribute_name: str, attribute_value: str, available_values: List[str]) -> None:
+        self.attribute_name = attribute_name
+        self.attribute_value = attribute_value
+        self.available_values = available_values
+        self.message = (
+            f"Unknown {attribute_name}: {attribute_value}."
+            + f"Available {attribute_name}s: {', '.join(available_values)}"
+        )
+        super().__init__(self.message)

src/exchange/moderators/__init__.py

@@ -1,6 +1,7 @@
 from functools import cache
 from typing import Type
 
+from exchange.load_exchange_attribute_error import LoadExchangeAttributeError
 from exchange.moderators.base import Moderator
 from exchange.utils import load_plugins
 from exchange.moderators.passive import PassiveModerator  # noqa
@@ -10,4 +11,7 @@
 
 @cache
 def get_moderator(name: str) -> Type[Moderator]:
-    return load_plugins(group="exchange.moderator")[name]
+    moderators = load_plugins(group="exchange.moderator")
+    if name not in moderators:
+        raise LoadExchangeAttributeError("moderator", name, moderators.keys())
+    return moderators[name]

src/exchange/providers/__init__.py

@@ -1,6 +1,7 @@
 from functools import cache
 from typing import Type
 
+from exchange.load_exchange_attribute_error import LoadExchangeAttributeError
 from exchange.providers.anthropic import AnthropicProvider  # noqa
 from exchange.providers.base import Provider, Usage  # noqa
 from exchange.providers.databricks import DatabricksProvider  # noqa
@@ -13,4 +14,7 @@
 
 @cache
 def get_provider(name: str) -> Type[Provider]:
-    return load_plugins(group="exchange.provider")[name]
+    providers = load_plugins(group="exchange.provider")
+    if name not in providers:
+        raise LoadExchangeAttributeError("provider", name, providers.keys())
+    return providers[name]

src/exchange/providers/anthropic.py

@@ -7,7 +7,7 @@
 from exchange.content import Text, ToolResult, ToolUse
 from exchange.providers.base import Provider, Usage
 from tenacity import retry, wait_fixed, stop_after_attempt
-from exchange.providers.utils import retry_if_status
+from exchange.providers.utils import get_provider_env_value, retry_if_status
 from exchange.providers.utils import raise_for_status
 
 ANTHROPIC_HOST = "https://api.anthropic.com/v1/messages"
@@ -27,10 +27,7 @@ def __init__(self, client: httpx.Client) -> None:
     @classmethod
     def from_env(cls: Type["AnthropicProvider"]) -> "AnthropicProvider":
         url = os.environ.get("ANTHROPIC_HOST", ANTHROPIC_HOST)
-        try:
-            key = os.environ["ANTHROPIC_API_KEY"]
-        except KeyError:
-            raise RuntimeError("Failed to get ANTHROPIC_API_KEY from the environment")
+        key = get_provider_env_value("ANTHROPIC_API_KEY", "anthropic")
         client = httpx.Client(
             base_url=url,
             headers={

src/exchange/providers/azure.py

@@ -1,9 +1,9 @@
-import os
 from typing import Type
 
 import httpx
 
 from exchange.providers import OpenAiProvider
+from exchange.providers.utils import get_provider_env_value
 
 
 class AzureProvider(OpenAiProvider):
@@ -14,25 +14,11 @@ def __init__(self, client: httpx.Client) -> None:
 
     @classmethod
     def from_env(cls: Type["AzureProvider"]) -> "AzureProvider":
-        try:
-            url = os.environ["AZURE_CHAT_COMPLETIONS_HOST_NAME"]
-        except KeyError:
-            raise RuntimeError("Failed to get AZURE_CHAT_COMPLETIONS_HOST_NAME from the environment.")
-
-        try:
-            deployment_name = os.environ["AZURE_CHAT_COMPLETIONS_DEPLOYMENT_NAME"]
-        except KeyError:
-            raise RuntimeError("Failed to get AZURE_CHAT_COMPLETIONS_DEPLOYMENT_NAME from the environment.")
-
-        try:
-            api_version = os.environ["AZURE_CHAT_COMPLETIONS_DEPLOYMENT_API_VERSION"]
-        except KeyError:
-            raise RuntimeError("Failed to get AZURE_CHAT_COMPLETIONS_DEPLOYMENT_API_VERSION from the environment.")
-
-        try:
-            key = os.environ["AZURE_CHAT_COMPLETIONS_KEY"]
-        except KeyError:
-            raise RuntimeError("Failed to get AZURE_CHAT_COMPLETIONS_KEY from the environment.")
+        url = cls._get_env_variable("AZURE_CHAT_COMPLETIONS_HOST_NAME")
+        deployment_name = cls._get_env_variable("AZURE_CHAT_COMPLETIONS_DEPLOYMENT_NAME")
+
+        api_version = cls._get_env_variable("AZURE_CHAT_COMPLETIONS_DEPLOYMENT_API_VERSION")
+        key = cls._get_env_variable("AZURE_CHAT_COMPLETIONS_KEY")
 
         # format the url host/"openai/deployments/" + deployment_name + "/?api-version=" + api_version
         url = f"{url}/openai/deployments/{deployment_name}/"
@@ -43,3 +29,7 @@ def from_env(cls: Type["AzureProvider"]) -> "AzureProvider":
             timeout=httpx.Timeout(60 * 10),
         )
         return cls(client)
+
+    @classmethod
+    def _get_env_variable(cls: Type["AzureProvider"], key: str) -> str:
+        return get_provider_env_value(key, "azure")

src/exchange/providers/base.py

@@ -1,6 +1,6 @@
 from abc import ABC, abstractmethod
 from attrs import define, field
-from typing import List, Tuple, Type
+from typing import List, Optional, Tuple, Type
 
 from exchange.message import Message
 from exchange.tool import Tool
@@ -28,3 +28,14 @@ def complete(
     ) -> Tuple[Message, Usage]:
         """Generate the next message using the specified model"""
         pass
+
+
+class MissingProviderEnvVariableError(Exception):
+    def __init__(self, env_variable: str, provider: str, instructions: Optional[str] = None) -> None:
+        self.env_variable = env_variable
+        self.provider = provider
+        self.instructions = instructions
+        self.message = f"Missing environment variable: {env_variable} for provider {provider}"
+        if instructions:
+            self.message += f". {instructions}"
+        super().__init__(self.message)

src/exchange/providers/bedrock.py

@@ -13,7 +13,7 @@
 from exchange.message import Message
 from exchange.providers import Provider, Usage
 from tenacity import retry, wait_fixed, stop_after_attempt
-from exchange.providers.utils import retry_if_status
+from exchange.providers.utils import get_provider_env_value, retry_if_status
 from exchange.providers.utils import raise_for_status
 from exchange.tool import Tool
 
@@ -154,12 +154,9 @@ def __init__(self, client: AwsClient) -> None:
     @classmethod
     def from_env(cls: Type["BedrockProvider"]) -> "BedrockProvider":
         aws_region = os.environ.get("AWS_REGION", "us-east-1")
-        try:
-            aws_access_key = os.environ["AWS_ACCESS_KEY_ID"]
-            aws_secret_key = os.environ["AWS_SECRET_ACCESS_KEY"]
-            aws_session_token = os.environ.get("AWS_SESSION_TOKEN")
-        except KeyError:
-            raise RuntimeError("Failed to get AWS_ACCESS_KEY_ID or AWS_SECRET_ACCESS_KEY from the environment")
+        aws_access_key = cls._get_env_variable("AWS_ACCESS_KEY_ID")
+        aws_secret_key = cls._get_env_variable("AWS_SECRET_ACCESS_KEY")
+        aws_session_token = cls._get_env_variable("AWS_SESSION_TOKEN")
 
         client = AwsClient(
             aws_region=aws_region,
@@ -326,3 +323,7 @@ def tools_to_bedrock_spec(tools: Tuple[Tool]) -> Optional[dict]:
             tools_added.add(tool.name)
         tool_config = {"tools": tool_config_list}
         return tool_config
+
+    @classmethod
+    def _get_env_variable(cls: Type["BedrockProvider"], key: str) -> str:
+        return get_provider_env_value(key, "bedrock")

src/exchange/providers/databricks.py

@@ -1,12 +1,11 @@
-import os
 from typing import Any, Dict, List, Tuple, Type
 
 import httpx
 
 from exchange.message import Message
 from exchange.providers.base import Provider, Usage
 from tenacity import retry, wait_fixed, stop_after_attempt
-from exchange.providers.utils import raise_for_status, retry_if_status
+from exchange.providers.utils import get_provider_env_value, raise_for_status, retry_if_status
 from exchange.providers.utils import (
     messages_to_openai_spec,
     openai_response_to_message,
@@ -37,18 +36,8 @@ def __init__(self, client: httpx.Client) -> None:
 
     @classmethod
     def from_env(cls: Type["DatabricksProvider"]) -> "DatabricksProvider":
-        try:
-            url = os.environ["DATABRICKS_HOST"]
-        except KeyError:
-            raise RuntimeError(
-                "Failed to get DATABRICKS_HOST from the environment. See https://docs.databricks.com/en/dev-tools/auth/index.html#general-host-token-and-account-id-environment-variables-and-fields"
-            )
-        try:
-            key = os.environ["DATABRICKS_TOKEN"]
-        except KeyError:
-            raise RuntimeError(
-                "Failed to get DATABRICKS_TOKEN from the environment. See https://docs.databricks.com/en/dev-tools/auth/index.html#general-host-token-and-account-id-environment-variables-and-fields"
-            )
+        url = cls._get_env_variable("DATABRICKS_HOST")
+        key = cls._get_env_variable("DATABRICKS_TOKEN")
         client = httpx.Client(
             base_url=url,
             auth=("token", key),
@@ -100,3 +89,8 @@ def _post(self, model: str, payload: dict) -> httpx.Response:
             json=payload,
         )
         return raise_for_status(response).json()
+
+    @classmethod
+    def _get_env_variable(cls: Type["DatabricksProvider"], key: str) -> str:
+        instruction = "https://docs.databricks.com/en/dev-tools/auth/index.html#general-host-token-and-account-id-environment-variables-and-fields"
+        return get_provider_env_value(key, "databricks", instruction)

src/exchange/providers/openai.py

@@ -6,6 +6,7 @@
 from exchange.message import Message
 from exchange.providers.base import Provider, Usage
 from exchange.providers.utils import (
+    get_provider_env_value,
     messages_to_openai_spec,
     openai_response_to_message,
     openai_single_message_context_length_exceeded,
@@ -36,12 +37,8 @@ def __init__(self, client: httpx.Client) -> None:
     @classmethod
     def from_env(cls: Type["OpenAiProvider"]) -> "OpenAiProvider":
         url = os.environ.get("OPENAI_HOST", OPENAI_HOST)
-        try:
-            key = os.environ["OPENAI_API_KEY"]
-        except KeyError:
-            raise RuntimeError(
-                "Failed to get OPENAI_API_KEY from the environment, see https://platform.openai.com/docs/api-reference/api-keys"
-            )
+        api_key_instructions = "see https://platform.openai.com/docs/api-reference/api-keys"
+        key = get_provider_env_value("OPENAI_API_KEY", "openai", api_key_instructions)
         client = httpx.Client(
             base_url=url + "v1/",
             auth=("Bearer", key),

src/exchange/providers/utils.py

@@ -1,11 +1,13 @@
 import base64
 import json
+import os
 import re
 from typing import Any, Callable, Dict, List, Optional, Tuple
 
 import httpx
 from exchange.content import Text, ToolResult, ToolUse
 from exchange.message import Message
+from exchange.providers.base import MissingProviderEnvVariableError
 from exchange.tool import Tool
 from tenacity import retry_if_exception
 
@@ -179,6 +181,13 @@ def openai_single_message_context_length_exceeded(error_dict: dict) -> None:
         raise InitialMessageTooLargeError(f"Input message too long. Message: {error_dict.get('message')}")
 
 
+def get_provider_env_value(env_variable: str, provider: str, instructions: Optional[str] = None) -> str:
+    try:
+        return os.environ[env_variable]
+    except KeyError:
+        raise MissingProviderEnvVariableError(env_variable, provider, instructions)
+
+
 class InitialMessageTooLargeError(Exception):
     """Custom error raised when the first input message in an exchange is too large."""
 

tests/providers/test_anthropic.py

@@ -6,6 +6,7 @@
 from exchange import Message, Text
 from exchange.content import ToolResult, ToolUse
 from exchange.providers.anthropic import AnthropicProvider
+from exchange.providers.base import MissingProviderEnvVariableError
 from exchange.tool import Tool
 
 
@@ -25,6 +26,15 @@ def anthropic_provider():
     return AnthropicProvider.from_env()
 
 
+def test_from_env_throw_error_when_missing_api_key():
+    with patch.dict(os.environ, {}, clear=True):
+        with pytest.raises(MissingProviderEnvVariableError) as context:
+            AnthropicProvider.from_env()
+        assert context.value.provider == "anthropic"
+        assert context.value.env_variable == "ANTHROPIC_API_KEY"
+        assert context.value.message == "Missing environment variable: ANTHROPIC_API_KEY for provider anthropic"
+
+
 def test_anthropic_response_to_text_message() -> None:
     response = {
         "content": [{"type": "text", "text": "Hello from Claude!"}],

tests/providers/test_azure.py

@@ -1,14 +1,44 @@
 import os
+from unittest.mock import patch
 
 import pytest
 
 from exchange import Text, ToolUse
 from exchange.providers.azure import AzureProvider
+from exchange.providers.base import MissingProviderEnvVariableError
 from .conftest import complete, tools
 
 AZURE_MODEL = os.getenv("AZURE_MODEL", "gpt-4o-mini")
 
 
+@pytest.mark.parametrize(
+    "env_var_name",
+    [
+        ("AZURE_CHAT_COMPLETIONS_HOST_NAME"),
+        ("AZURE_CHAT_COMPLETIONS_DEPLOYMENT_NAME"),
+        ("AZURE_CHAT_COMPLETIONS_DEPLOYMENT_API_VERSION"),
+        ("AZURE_CHAT_COMPLETIONS_KEY"),
+    ],
+)
+def test_from_env_throw_error_when_missing_env_var(env_var_name):
+    with patch.dict(
+        os.environ,
+        {
+            "AZURE_CHAT_COMPLETIONS_HOST_NAME": "test_host_name",
+            "AZURE_CHAT_COMPLETIONS_DEPLOYMENT_NAME": "test_deployment_name",
+            "AZURE_CHAT_COMPLETIONS_DEPLOYMENT_API_VERSION": "test_api_version",
+            "AZURE_CHAT_COMPLETIONS_KEY": "test_api_key",
+        },
+        clear=True,
+    ):
+        os.environ.pop(env_var_name)
+        with pytest.raises(MissingProviderEnvVariableError) as context:
+            AzureProvider.from_env()
+        assert context.value.provider == "azure"
+        assert context.value.env_variable == env_var_name
+        assert context.value.message == f"Missing environment variable: {env_var_name} for provider azure"
+
+
 @pytest.mark.vcr()
 def test_azure_complete(default_azure_env):
     reply_message, reply_usage = complete(AzureProvider, AZURE_MODEL)

tests/providers/test_bedrock.py

@@ -5,12 +5,39 @@
 import pytest
 from exchange.content import Text, ToolResult, ToolUse
 from exchange.message import Message
+from exchange.providers.base import MissingProviderEnvVariableError
 from exchange.providers.bedrock import BedrockProvider
 from exchange.tool import Tool
 
 logger = logging.getLogger(__name__)
 
 
+@pytest.mark.parametrize(
+    "env_var_name",
+    [
+        ("AWS_ACCESS_KEY_ID"),
+        ("AWS_SECRET_ACCESS_KEY"),
+        ("AWS_SESSION_TOKEN"),
+    ],
+)
+def test_from_env_throw_error_when_missing_env_var(env_var_name):
+    with patch.dict(
+        os.environ,
+        {
+            "AWS_ACCESS_KEY_ID": "test_access_key_id",
+            "AWS_SECRET_ACCESS_KEY": "test_secret_access_key",
+            "AWS_SESSION_TOKEN": "test_session_token",
+        },
+        clear=True,
+    ):
+        os.environ.pop(env_var_name)
+        with pytest.raises(MissingProviderEnvVariableError) as context:
+            BedrockProvider.from_env()
+        assert context.value.provider == "bedrock"
+        assert context.value.env_variable == env_var_name
+        assert context.value.message == f"Missing environment variable: {env_var_name} for provider bedrock"
+
+
 @pytest.fixture
 @patch.dict(
     os.environ,