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feat: add logging hook (#577)
* feat: add logging hook Signed-off-by: Danju Visvanathan <danju.visvanathan@gmail.com> * refactor: split logginghook into separate module Signed-off-by: Danju Visvanathan <danju.visvanathan@gmail.com> * chore: update README.md Signed-off-by: Danju Visvanathan <danju.visvanathan@gmail.com> * fix: consistent appending to args Signed-off-by: Danju Visvanathan <danju.visvanathan@gmail.com> * chore: fmt Signed-off-by: Danju Visvanathan <danju.visvanathan@gmail.com> * revert: refactor of hook package Signed-off-by: Danju Visvanathan <danju.visvanathan@gmail.com> * fix: parameterise stage key Signed-off-by: Danju Visvanathan <danju.visvanathan@gmail.com> * refactor: parameterise stage value Signed-off-by: Danju Visvanathan <danju.visvanathan@gmail.com> * fix: use asdict() Signed-off-by: Danju Visvanathan <danju.visvanathan@gmail.com> * fix: change log message to not duplicate stage Signed-off-by: Danju Visvanathan <danju.visvanathan@gmail.com> * fix: propogate error_message to avoid silently dropping it Signed-off-by: Danju Visvanathan <danju.visvanathan@gmail.com> --------- Signed-off-by: Danju Visvanathan <danju.visvanathan@gmail.com> Co-authored-by: Anton Grübel <anton.gruebel@gmail.com>
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‎README.md‎

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@@ -190,6 +190,17 @@ client.get_boolean_flag("my-flag", False, flag_evaluation_options=options)
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The OpenFeature SDK logs to the `openfeature` logger using the `logging` package from the Python Standard Library.
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#### Logging Hook
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The Python SDK includes a `LoggingHook`, which logs detailed information at key points during flag evaluation, using the `logging` package. This hook can be particularly helpful for troubleshooting and debugging; simply attach it at the global, client or invocation level and ensure your log level is set to "debug".
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```python
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from openfeature import api
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from openfeature.hook.logging_hook import LoggingHook
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api.add_hooks([LoggingHook()])
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```
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### Domains
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Clients can be assigned to a domain.

‎openfeature/hook/logging_hook.py‎

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import json
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import logging
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from dataclasses import asdict
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from openfeature.evaluation_context import EvaluationContext
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from openfeature.exception import ErrorCode, OpenFeatureError
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from openfeature.flag_evaluation import FlagEvaluationDetails, FlagValueType
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from openfeature.hook import Hook, HookContext, HookHints
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class LoggingHook(Hook):
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def __init__(
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self,
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include_evaluation_context: bool = False,
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logger: logging.Logger | None = None,
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):
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self.logger = logger or logging.getLogger("openfeature")
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self.include_evaluation_context = include_evaluation_context
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def _build_args(self, hook_context: HookContext, stage: str) -> dict:
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args = {
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"domain": hook_context.client_metadata.domain
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if hook_context.client_metadata
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else None,
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"provider_name": hook_context.provider_metadata.name
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if hook_context.provider_metadata
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else None,
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"flag_key": hook_context.flag_key,
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"default_value": hook_context.default_value,
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"stage": stage,
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}
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if self.include_evaluation_context:
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args["evaluation_context"] = json.dumps(
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asdict(hook_context.evaluation_context),
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default=str,
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)
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return args
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def before(
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self, hook_context: HookContext, hints: HookHints
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) -> EvaluationContext | None:
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args = self._build_args(hook_context, "before")
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self.logger.debug("Flag evaluation %s", args)
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return None
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def after(
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self,
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hook_context: HookContext,
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details: FlagEvaluationDetails[FlagValueType],
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hints: HookHints,
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) -> None:
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args = self._build_args(hook_context, "after")
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args["reason"] = details.reason
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args["variant"] = details.variant
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args["value"] = details.value
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self.logger.debug("Flag evaluation %s", args)
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def error(
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self, hook_context: HookContext, exception: Exception, hints: HookHints
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) -> None:
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args = self._build_args(hook_context, "error")
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if isinstance(exception, OpenFeatureError):
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args["error_code"] = exception.error_code
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args["error_message"] = exception.error_message
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else:
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args["error_code"] = ErrorCode.GENERAL
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args["error_message"] = str(exception)
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self.logger.error("Flag evaluation %s", args)

‎tests/hook/test_logging_hook.py‎

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from unittest.mock import MagicMock
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import pytest
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from openfeature.client import ClientMetadata
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from openfeature.evaluation_context import EvaluationContext
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from openfeature.exception import ErrorCode, FlagNotFoundError
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from openfeature.flag_evaluation import FlagEvaluationDetails, FlagType
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from openfeature.hook.logging_hook import HookContext, LoggingHook
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from openfeature.provider.metadata import Metadata
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@pytest.fixture()
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def hook_context():
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return HookContext(
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flag_key="my-flag",
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flag_type=FlagType.BOOLEAN,
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default_value=False,
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evaluation_context=EvaluationContext("user-1", {"env": "prod"}),
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client_metadata=ClientMetadata(domain="my-domain"),
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provider_metadata=Metadata(name="my-provider"),
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)
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def test_before_calls_debug_with_stage(hook_context):
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mock_logger = MagicMock()
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hook = LoggingHook(logger=mock_logger)
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hook.before(hook_context, hints={})
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mock_logger.debug.assert_called_with(
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"Flag evaluation %s",
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{
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"stage": "before",
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"flag_key": "my-flag",
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"default_value": False,
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"domain": "my-domain",
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"provider_name": "my-provider",
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},
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)
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def test_after_calls_debug_with_stage(hook_context):
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mock_logger = MagicMock()
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hook = LoggingHook(logger=mock_logger)
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details = FlagEvaluationDetails(
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flag_key="my-flag",
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value=True,
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variant="on",
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reason="STATIC",
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)
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hook.after(hook_context, details, hints={})
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mock_logger.debug.assert_called_with(
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"Flag evaluation %s",
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{
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"stage": "after",
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"flag_key": "my-flag",
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"default_value": False,
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"domain": "my-domain",
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"provider_name": "my-provider",
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"reason": "STATIC",
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"variant": "on",
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"value": True,
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},
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)
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def test_after_calls_debug_with_evaluation_context(hook_context):
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mock_logger = MagicMock()
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hook = LoggingHook(logger=mock_logger, include_evaluation_context=True)
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details = FlagEvaluationDetails(
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flag_key="my-flag",
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value=True,
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variant="on",
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reason="STATIC",
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)
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hook.after(hook_context, details, hints={})
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mock_logger.debug.assert_called_with(
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"Flag evaluation %s",
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{
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"stage": "after",
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"flag_key": "my-flag",
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"default_value": False,
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"domain": "my-domain",
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"provider_name": "my-provider",
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"reason": "STATIC",
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"variant": "on",
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"value": True,
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"evaluation_context": '{"targeting_key": "user-1", "attributes": {"env": "prod"}}',
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},
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)
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def test_error_calls_error_log(hook_context):
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mock_logger = MagicMock()
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hook = LoggingHook(logger=mock_logger)
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exception = Exception("something went wrong")
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hook.error(hook_context, exception, hints={})
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mock_logger.error.assert_called_with(
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"Flag evaluation %s",
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{
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"stage": "error",
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"flag_key": "my-flag",
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"default_value": False,
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"domain": "my-domain",
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"provider_name": "my-provider",
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"error_code": ErrorCode.GENERAL,
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"error_message": "something went wrong",
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},
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)
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def test_error_extracts_error_code_from_open_feature_error(hook_context):
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mock_logger = MagicMock()
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hook = LoggingHook(logger=mock_logger)
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exception = FlagNotFoundError("flag not found")
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hook.error(hook_context, exception, hints={})
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mock_logger.error.assert_called_with(
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"Flag evaluation %s",
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{
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"stage": "error",
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"flag_key": "my-flag",
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"default_value": False,
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"domain": "my-domain",
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"provider_name": "my-provider",
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"error_code": ErrorCode.FLAG_NOT_FOUND,
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"error_message": "flag not found",
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},
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)
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def test_build_args_without_metadata():
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hook = LoggingHook()
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ctx = HookContext(
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flag_key="flag",
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flag_type=FlagType.STRING,
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default_value="default",
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evaluation_context=EvaluationContext(None, {}),
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client_metadata=None,
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provider_metadata=None,
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)
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result = hook._build_args(ctx, "before")
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assert result == {
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"flag_key": "flag",
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"default_value": "default",
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"domain": None,
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"provider_name": None,
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"stage": "before",
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}
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def test_build_args_excludes_evaluation_context_by_default(hook_context):
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hook = LoggingHook()
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result = hook._build_args(hook_context, "before")
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assert result == {
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"flag_key": "my-flag",
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"default_value": False,
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"domain": "my-domain",
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"provider_name": "my-provider",
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"stage": "before",
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}
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def test_build_args_includes_evaluation_context_when_enabled(hook_context):
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hook = LoggingHook(include_evaluation_context=True)
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result = hook._build_args(hook_context, "after")
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assert result == {
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"flag_key": "my-flag",
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"default_value": False,
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"domain": "my-domain",
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"provider_name": "my-provider",
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"evaluation_context": '{"targeting_key": "user-1", "attributes": {"env": "prod"}}',
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"stage": "after",
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}
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def test_error_calls_error_log_with_evaluation_context(hook_context):
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mock_logger = MagicMock()
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hook = LoggingHook(logger=mock_logger, include_evaluation_context=True)
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exception = Exception("something went wrong")
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hook.error(hook_context, exception, hints={})
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mock_logger.error.assert_called_with(
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"Flag evaluation %s",
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{
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"stage": "error",
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"flag_key": "my-flag",
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"default_value": False,
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"domain": "my-domain",
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"provider_name": "my-provider",
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"evaluation_context": '{"targeting_key": "user-1", "attributes": {"env": "prod"}}',
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"error_code": ErrorCode.GENERAL,
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"error_message": "something went wrong",
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},
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)

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