refactor: introduce StreamingNotSupportedError exception

Replace InvalidRailsConfigurationError with a new, more specific
StreamingNotSupportedError for cases where streaming is requested but
not
supported by the configuration. Update all relevant imports, usages, and
tests to use the new exception. This improves error clarity and guidance
for users encountering streaming configuration issues.

Author: Pouyanpi

nemoguardrails/cli/chat.py

@@ -28,7 +28,7 @@
 from nemoguardrails.colang.v2_x.runtime.eval import eval_expression
 from nemoguardrails.colang.v2_x.runtime.flows import State
 from nemoguardrails.colang.v2_x.runtime.runtime import RuntimeV2_x
-from nemoguardrails.exceptions import InvalidRailsConfigurationError
+from nemoguardrails.exceptions import StreamingNotSupportedError
 from nemoguardrails.logging import verbose
 from nemoguardrails.logging.verbose import console
 from nemoguardrails.rails.llm.options import (
@@ -93,22 +93,19 @@ async def _run_chat_v1_0(
 
                     bot_message_text = "".join(bot_message_list)
                     bot_message = {"role": "assistant", "content": bot_message_text}
-                except InvalidRailsConfigurationError as e:
-                    error_msg = str(e)
-                    if "stream_async()" in error_msg and "output rails" in error_msg:
-                        raise InvalidRailsConfigurationError(
-                            f"Cannot use --streaming with config `{config_path}` because output rails "
-                            "are configured but streaming is not enabled for them.\n\n"
-                            "To fix this, either:\n"
-                            "  1. Enable streaming for output rails by adding to your config.yml:\n"
-                            "     rails:\n"
-                            "       output:\n"
-                            "         streaming:\n"
-                            "           enabled: True\n\n"
-                            "  2. Or run without the --streaming flag:\n"
-                            f"     nemoguardrails chat {config_path}"
-                        ) from e
-                    raise
+                except StreamingNotSupportedError as e:
+                    raise StreamingNotSupportedError(
+                        f"Cannot use --streaming with config `{config_path}` because output rails "
+                        "are configured but streaming is not enabled for them.\n\n"
+                        "To fix this, either:\n"
+                        "  1. Enable streaming for output rails by adding to your config.yml:\n"
+                        "     rails:\n"
+                        "       output:\n"
+                        "         streaming:\n"
+                        "           enabled: True\n\n"
+                        "  2. Or run without the --streaming flag:\n"
+                        f"     nemoguardrails chat {config_path}"
+                    ) from e
 
             else:
                 if rails_app is None:

nemoguardrails/exceptions.py

@@ -19,6 +19,7 @@
     "InvalidModelConfigurationError",
     "InvalidRailsConfigurationError",
     "LLMCallException",
+    "StreamingNotSupportedError",
 ]
 
 
@@ -49,6 +50,12 @@ class InvalidRailsConfigurationError(ConfigurationError):
     pass
 
 
+class StreamingNotSupportedError(InvalidRailsConfigurationError):
+    """Raised when streaming is requested but not supported by the configuration."""
+
+    pass
+
+
 class LLMCallException(Exception):
     """A wrapper around the LLM call invocation exception.
 

nemoguardrails/rails/llm/llmrails.py

@@ -73,6 +73,7 @@
 from nemoguardrails.exceptions import (
     InvalidModelConfigurationError,
     InvalidRailsConfigurationError,
+    StreamingNotSupportedError,
 )
 from nemoguardrails.kb.kb import KnowledgeBase
 from nemoguardrails.llm.cache import CacheInterface, LFUCache
@@ -1167,7 +1168,7 @@ def _validate_streaming_with_output_rails(self) -> None:
         if len(self.config.rails.output.flows) > 0 and (
             not self.config.rails.output.streaming or not self.config.rails.output.streaming.enabled
         ):
-            raise InvalidRailsConfigurationError(
+            raise StreamingNotSupportedError(
                 "stream_async() cannot be used when output rails are configured but "
                 "rails.output.streaming.enabled is False. Either set "
                 "rails.output.streaming.enabled to True in your configuration, or use "

tests/test_parallel_streaming_output_rails.py

@@ -24,7 +24,7 @@
 
 from nemoguardrails import RailsConfig
 from nemoguardrails.actions import action
-from nemoguardrails.exceptions import InvalidRailsConfigurationError
+from nemoguardrails.exceptions import StreamingNotSupportedError
 from tests.utils import TestChat
 
 
@@ -586,7 +586,7 @@ async def test_parallel_streaming_output_rails_default_config_behavior(
 
     llmrails = LLMRails(parallel_output_rails_default_config)
 
-    with pytest.raises(InvalidRailsConfigurationError) as exc_info:
+    with pytest.raises(StreamingNotSupportedError) as exc_info:
         async for _ in llmrails.stream_async(messages=[{"role": "user", "content": "Hi!"}]):
             pass
 

tests/test_streaming.py

@@ -21,7 +21,7 @@
 
 from nemoguardrails import RailsConfig
 from nemoguardrails.actions import action
-from nemoguardrails.exceptions import InvalidRailsConfigurationError
+from nemoguardrails.exceptions import StreamingNotSupportedError
 from nemoguardrails.streaming import StreamingHandler
 from tests.utils import TestChat
 
@@ -494,7 +494,7 @@ async def test_streaming_with_output_rails_disabled_raises_error():
         streaming=True,
     )
 
-    with pytest.raises(InvalidRailsConfigurationError) as exc_info:
+    with pytest.raises(StreamingNotSupportedError) as exc_info:
         async for chunk in chat.app.stream_async(
             messages=[{"role": "user", "content": "Hi!"}],
         ):
@@ -536,7 +536,7 @@ async def test_streaming_with_output_rails_no_streaming_config_raises_error():
         streaming=True,
     )
 
-    with pytest.raises(InvalidRailsConfigurationError) as exc_info:
+    with pytest.raises(StreamingNotSupportedError) as exc_info:
         async for chunk in chat.app.stream_async(
             messages=[{"role": "user", "content": "Hi!"}],
         ):

tests/test_streaming_output_rails.py

@@ -23,7 +23,7 @@
 
 from nemoguardrails import RailsConfig
 from nemoguardrails.actions import action
-from nemoguardrails.exceptions import InvalidRailsConfigurationError
+from nemoguardrails.exceptions import StreamingNotSupportedError
 from nemoguardrails.rails.llm.llmrails import LLMRails
 from nemoguardrails.streaming import StreamingHandler
 from tests.utils import TestChat
@@ -165,7 +165,7 @@ async def test_streaming_output_rails_blocked_default_config(
 
     llmrails = LLMRails(output_rails_streaming_config_default)
 
-    with pytest.raises(InvalidRailsConfigurationError) as exc_info:
+    with pytest.raises(StreamingNotSupportedError) as exc_info:
         async for chunk in llmrails.stream_async(messages=[{"role": "user", "content": "Hi!"}]):
             pass