refactor: replace exception raising with error flag resolution

openfeature/client.py

@@ -446,12 +446,12 @@ def _establish_hooks_and_provider(
 
     def _assert_provider_status(
         self,
-    ) -> None:
+    ) -> typing.Optional[OpenFeatureError]:
         status = self.get_provider_status()
         if status == ProviderStatus.NOT_READY:
-            raise ProviderNotReadyError()
+            return ProviderNotReadyError()
         if status == ProviderStatus.FATAL:
-            raise ProviderFatalError()
+            return ProviderFatalError()
         return None
 
     def _before_hooks_and_merge_context(
@@ -511,7 +511,22 @@ async def evaluate_flag_details_async(
         )
 
         try:
-            self._assert_provider_status()
+            if provider_err := self._assert_provider_status():
+                error_hooks(
+                    flag_type,
+                    hook_context,
+                    provider_err,
+                    reversed_merged_hooks,
+                    hook_hints,
+                )
+                flag_evaluation = FlagEvaluationDetails(
+                    flag_key=flag_key,
+                    value=default_value,
+                    reason=Reason.ERROR,
+                    error_code=provider_err.error_code,
+                    error_message=provider_err.error_message,
+                )
+                return flag_evaluation
 
             merged_context = self._before_hooks_and_merge_context(
                 flag_type,
@@ -528,6 +543,11 @@ async def evaluate_flag_details_async(
                 default_value,
                 merged_context,
             )
+            if err := flag_evaluation.get_exception():
+                error_hooks(
+                    flag_type, hook_context, err, reversed_merged_hooks, hook_hints
+                )
+                return flag_evaluation
 
             after_hooks(
                 flag_type,
@@ -607,7 +627,22 @@ def evaluate_flag_details(
         )
 
         try:
-            self._assert_provider_status()
+            if provider_err := self._assert_provider_status():
+                error_hooks(
+                    flag_type,
+                    hook_context,
+                    provider_err,
+                    reversed_merged_hooks,
+                    hook_hints,
+                )
+                flag_evaluation = FlagEvaluationDetails(
+                    flag_key=flag_key,
+                    value=default_value,
+                    reason=Reason.ERROR,
+                    error_code=provider_err.error_code,
+                    error_message=provider_err.error_message,
+                )
+                return flag_evaluation
 
             merged_context = self._before_hooks_and_merge_context(
                 flag_type,
@@ -624,6 +659,12 @@ def evaluate_flag_details(
                 default_value,
                 merged_context,
             )
+            if err := flag_evaluation.get_exception():
+                error_hooks(
+                    flag_type, hook_context, err, reversed_merged_hooks, hook_hints
+                )
+                flag_evaluation.value = default_value
+                return flag_evaluation
 
             after_hooks(
                 flag_type,
@@ -693,27 +734,33 @@ async def _create_provider_evaluation_async(
         }
         get_details_callable = get_details_callables_async.get(flag_type)
         if not get_details_callable:
-            raise GeneralError(error_message="Unknown flag type")
+            return FlagEvaluationDetails(
+                flag_key=flag_key,
+                value=default_value,
+                reason=Reason.ERROR,
+                error_code=ErrorCode.GENERAL,
+                error_message="Unknown flag type",
+            )
 
         resolution = await get_details_callable(
             flag_key=flag_key,
             default_value=default_value,
             evaluation_context=evaluation_context,
         )
-        resolution.raise_for_error()
+        if resolution.error_code:
+            return resolution.to_flag_evaluation_details(flag_key)
 
         # we need to check the get_args to be compatible with union types.
-        _typecheck_flag_value(resolution.value, flag_type)
+        if err := _typecheck_flag_value(value=resolution.value, flag_type=flag_type):
+            return FlagEvaluationDetails(
+                flag_key=flag_key,
+                value=resolution.value,
+                reason=Reason.ERROR,
+                error_code=err.error_code,
+                error_message=err.error_message,
+            )
 
-        return FlagEvaluationDetails(
-            flag_key=flag_key,
-            value=resolution.value,
-            variant=resolution.variant,
-            flag_metadata=resolution.flag_metadata or {},
-            reason=resolution.reason,
-            error_code=resolution.error_code,
-            error_message=resolution.error_message,
-        )
+        return resolution.to_flag_evaluation_details(flag_key)
 
     def _create_provider_evaluation(
         self,
@@ -743,27 +790,33 @@ def _create_provider_evaluation(
 
         get_details_callable = get_details_callables.get(flag_type)
         if not get_details_callable:
-            raise GeneralError(error_message="Unknown flag type")
+            return FlagEvaluationDetails(
+                flag_key=flag_key,
+                value=default_value,
+                reason=Reason.ERROR,
+                error_code=ErrorCode.GENERAL,
+                error_message="Unknown flag type",
+            )
 
         resolution = get_details_callable(
             flag_key=flag_key,
             default_value=default_value,
             evaluation_context=evaluation_context,
         )
-        resolution.raise_for_error()
+        if resolution.error_code:
+            return resolution.to_flag_evaluation_details(flag_key)
 
         # we need to check the get_args to be compatible with union types.
-        _typecheck_flag_value(resolution.value, flag_type)
+        if err := _typecheck_flag_value(value=resolution.value, flag_type=flag_type):
+            return FlagEvaluationDetails(
+                flag_key=flag_key,
+                value=resolution.value,
+                reason=Reason.ERROR,
+                error_code=err.error_code,
+                error_message=err.error_message,
+            )
 
-        return FlagEvaluationDetails(
-            flag_key=flag_key,
-            value=resolution.value,
-            variant=resolution.variant,
-            flag_metadata=resolution.flag_metadata or {},
-            reason=resolution.reason,
-            error_code=resolution.error_code,
-            error_message=resolution.error_message,
-        )
+        return resolution.to_flag_evaluation_details(flag_key)
 
     def add_handler(self, event: ProviderEvent, handler: EventHandler) -> None:
         _event_support.add_client_handler(self, event, handler)
@@ -772,7 +825,9 @@ def remove_handler(self, event: ProviderEvent, handler: EventHandler) -> None:
         _event_support.remove_client_handler(self, event, handler)
 
 
-def _typecheck_flag_value(value: typing.Any, flag_type: FlagType) -> None:
+def _typecheck_flag_value(
+    value: typing.Any, flag_type: FlagType
+) -> typing.Optional[OpenFeatureError]:
     type_map: TypeMap = {
         FlagType.BOOLEAN: bool,
         FlagType.STRING: str,
@@ -782,6 +837,7 @@ def _typecheck_flag_value(value: typing.Any, flag_type: FlagType) -> None:
     }
     _type = type_map.get(flag_type)
     if not _type:
-        raise GeneralError(error_message="Unknown flag type")
+        return GeneralError(error_message="Unknown flag type")
     if not isinstance(value, _type):
-        raise TypeMismatchError(f"Expected type {_type} but got {type(value)}")
+        return TypeMismatchError(f"Expected type {_type} but got {type(value)}")
+    return None

openfeature/flag_evaluation.py

@@ -4,7 +4,7 @@
 from dataclasses import dataclass, field
 
 from openfeature._backports.strenum import StrEnum
-from openfeature.exception import ErrorCode
+from openfeature.exception import ErrorCode, OpenFeatureError
 
 if typing.TYPE_CHECKING:  # pragma: no cover
     # resolves a circular dependency in type annotations
@@ -56,6 +56,11 @@ class FlagEvaluationDetails(typing.Generic[T_co]):
     error_code: typing.Optional[ErrorCode] = None
     error_message: typing.Optional[str] = None
 
+    def get_exception(self) -> typing.Optional[OpenFeatureError]:
+        if self.error_code:
+            return ErrorCode.to_exception(self.error_code, self.error_message or "")
+        return None
+
 
 @dataclass
 class FlagEvaluationOptions:
@@ -79,3 +84,14 @@ def raise_for_error(self) -> None:
         if self.error_code:
             raise ErrorCode.to_exception(self.error_code, self.error_message or "")
         return None
+
+    def to_flag_evaluation_details(self, flag_key: str) -> FlagEvaluationDetails[U_co]:
+        return FlagEvaluationDetails(
+            flag_key=flag_key,
+            value=self.value,
+            variant=self.variant,
+            flag_metadata=self.flag_metadata,
+            reason=self.reason,
+            error_code=self.error_code,
+            error_message=self.error_message,
+        )

openfeature/provider/in_memory_provider.py

@@ -3,7 +3,7 @@
 
 from openfeature._backports.strenum import StrEnum
 from openfeature.evaluation_context import EvaluationContext
-from openfeature.exception import FlagNotFoundError
+from openfeature.exception import ErrorCode
 from openfeature.flag_evaluation import FlagMetadata, FlagResolutionDetails, Reason
 from openfeature.hook import Hook
 from openfeature.provider import AbstractProvider, Metadata
@@ -74,93 +74,100 @@ def resolve_boolean_details(
         default_value: bool,
         evaluation_context: typing.Optional[EvaluationContext] = None,
     ) -> FlagResolutionDetails[bool]:
-        return self._resolve(flag_key, evaluation_context)
+        return self._resolve(flag_key, default_value, evaluation_context)
 
     async def resolve_boolean_details_async(
         self,
         flag_key: str,
         default_value: bool,
         evaluation_context: typing.Optional[EvaluationContext] = None,
     ) -> FlagResolutionDetails[bool]:
-        return await self._resolve_async(flag_key, evaluation_context)
+        return await self._resolve_async(flag_key, default_value, evaluation_context)
 
     def resolve_string_details(
         self,
         flag_key: str,
         default_value: str,
         evaluation_context: typing.Optional[EvaluationContext] = None,
     ) -> FlagResolutionDetails[str]:
-        return self._resolve(flag_key, evaluation_context)
+        return self._resolve(flag_key, default_value, evaluation_context)
 
     async def resolve_string_details_async(
         self,
         flag_key: str,
         default_value: str,
         evaluation_context: typing.Optional[EvaluationContext] = None,
     ) -> FlagResolutionDetails[str]:
-        return await self._resolve_async(flag_key, evaluation_context)
+        return await self._resolve_async(flag_key, default_value, evaluation_context)
 
     def resolve_integer_details(
         self,
         flag_key: str,
         default_value: int,
         evaluation_context: typing.Optional[EvaluationContext] = None,
     ) -> FlagResolutionDetails[int]:
-        return self._resolve(flag_key, evaluation_context)
+        return self._resolve(flag_key, default_value, evaluation_context)
 
     async def resolve_integer_details_async(
         self,
         flag_key: str,
         default_value: int,
         evaluation_context: typing.Optional[EvaluationContext] = None,
     ) -> FlagResolutionDetails[int]:
-        return await self._resolve_async(flag_key, evaluation_context)
+        return await self._resolve_async(flag_key, default_value, evaluation_context)
 
     def resolve_float_details(
         self,
         flag_key: str,
         default_value: float,
         evaluation_context: typing.Optional[EvaluationContext] = None,
     ) -> FlagResolutionDetails[float]:
-        return self._resolve(flag_key, evaluation_context)
+        return self._resolve(flag_key, default_value, evaluation_context)
 
     async def resolve_float_details_async(
         self,
         flag_key: str,
         default_value: float,
         evaluation_context: typing.Optional[EvaluationContext] = None,
     ) -> FlagResolutionDetails[float]:
-        return await self._resolve_async(flag_key, evaluation_context)
+        return await self._resolve_async(flag_key, default_value, evaluation_context)
 
     def resolve_object_details(
         self,
         flag_key: str,
         default_value: typing.Union[dict, list],
         evaluation_context: typing.Optional[EvaluationContext] = None,
     ) -> FlagResolutionDetails[typing.Union[dict, list]]:
-        return self._resolve(flag_key, evaluation_context)
+        return self._resolve(flag_key, default_value, evaluation_context)
 
     async def resolve_object_details_async(
         self,
         flag_key: str,
         default_value: typing.Union[dict, list],
         evaluation_context: typing.Optional[EvaluationContext] = None,
     ) -> FlagResolutionDetails[typing.Union[dict, list]]:
-        return await self._resolve_async(flag_key, evaluation_context)
+        return await self._resolve_async(flag_key, default_value, evaluation_context)
 
     def _resolve(
         self,
         flag_key: str,
+        default_value: V,
         evaluation_context: typing.Optional[EvaluationContext],
     ) -> FlagResolutionDetails[V]:
         flag = self._flags.get(flag_key)
         if flag is None:
-            raise FlagNotFoundError(f"Flag '{flag_key}' not found")
+            return FlagResolutionDetails(
+                value=default_value,
+                reason=Reason.ERROR,
+                error_code=ErrorCode.FLAG_NOT_FOUND,
+                error_message=f"Flag '{flag_key}' not found",
+            )
         return flag.resolve(evaluation_context)
 
     async def _resolve_async(
         self,
         flag_key: str,
+        default_value: V,
         evaluation_context: typing.Optional[EvaluationContext],
     ) -> FlagResolutionDetails[V]:
-        return self._resolve(flag_key, evaluation_context)
+        return self._resolve(flag_key, default_value, evaluation_context)

tests/provider/test_in_memory_provider.py

@@ -2,7 +2,7 @@
 
 import pytest
 
-from openfeature.exception import FlagNotFoundError
+from openfeature.exception import ErrorCode
 from openfeature.flag_evaluation import FlagResolutionDetails, Reason
 from openfeature.provider.in_memory_provider import InMemoryFlag, InMemoryProvider
 
@@ -22,11 +22,18 @@ async def test_should_handle_unknown_flags_correctly():
     # Given
     provider = InMemoryProvider({})
     # When
-    with pytest.raises(FlagNotFoundError):
-        provider.resolve_boolean_details(flag_key="Key", default_value=True)
-    with pytest.raises(FlagNotFoundError):
-        await provider.resolve_integer_details_async(flag_key="Key", default_value=1)
+    flag_sync = provider.resolve_boolean_details(flag_key="Key", default_value=True)
+    flag_async = await provider.resolve_boolean_details_async(
+        flag_key="Key", default_value=True
+    )
     # Then
+    assert flag_sync == flag_async
+    for flag in [flag_sync, flag_async]:
+        assert flag is not None
+        assert flag.value is True
+        assert flag.reason == Reason.ERROR
+        assert flag.error_code == ErrorCode.FLAG_NOT_FOUND
+        assert flag.error_message == "Flag 'Key' not found"
 
 
 @pytest.mark.asyncio