Move feature-flag evaluation onto context with OpenFeature-style API

Add get_boolean_value/get_string_value/get_integer_value/get_float_value/
get_object_value methods to CouchersContext, mirroring the OpenFeature
evaluation API and requiring an in-code default per call. All methods
(including boolean) now evaluate via the GrowthBook SDK's get_feature_value
so the in-code default is honored when a flag isn't set up yet - the old
check_gate used is_on(), which hardcoded False for missing flags.

Relocate the type-only CouchersContext imports in db.py and sql.py under
TYPE_CHECKING to avoid a context -> experimentation -> db/sql -> context
import cycle.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: aapeliv

app/backend/src/couchers/context.py

@@ -2,6 +2,7 @@
 
 import grpc
 
+from couchers import experimentation
 from couchers.i18n import LocalizationContext
 
 if TYPE_CHECKING:
@@ -179,6 +180,22 @@ def token(self) -> str:
     def localization(self) -> LocalizationContext:
         return self.__localization
 
+    # Feature-flag evaluation methods mirror the OpenFeature evaluation API.
+    def get_boolean_value(self, flag_key: str, default: bool) -> bool:
+        return experimentation.evaluate_boolean(self, flag_key, default)
+
+    def get_string_value(self, flag_key: str, default: str) -> str:
+        return experimentation.evaluate_value(self, flag_key, default)
+
+    def get_integer_value(self, flag_key: str, default: int) -> int:
+        return experimentation.evaluate_value(self, flag_key, default)
+
+    def get_float_value(self, flag_key: str, default: float) -> float:
+        return experimentation.evaluate_value(self, flag_key, default)
+
+    def get_object_value[T](self, flag_key: str, default: T) -> T:
+        return experimentation.evaluate_value(self, flag_key, default)
+
 
 def make_interactive_context(
     grpc_context: grpc.ServicerContext,

app/backend/src/couchers/db.py

@@ -6,6 +6,7 @@
 from contextlib import contextmanager
 from os import getpid
 from threading import get_ident
+from typing import TYPE_CHECKING
 
 from alembic import command
 from alembic.config import Config
@@ -19,7 +20,6 @@
 
 from couchers.config import config
 from couchers.constants import SERVER_THREADS, WORKER_THREADS
-from couchers.context import CouchersContext
 from couchers.models import (
     Cluster,
     ClusterRole,
@@ -33,6 +33,9 @@
 )
 from couchers.sql import where_users_column_visible
 
+if TYPE_CHECKING:
+    from couchers.context import CouchersContext
+
 # Register psycopg (psycopg3) as the default driver for postgresql:// URLs
 # This must happen before any engine is created
 registry.register("postgresql", "sqlalchemy.dialects.postgresql.psycopg", "PGDialect_psycopg")

app/backend/src/couchers/experimentation.py

@@ -174,29 +174,32 @@ def on_experiment_viewed(experiment: Experiment, result: Result, **kwargs: Any)
     return gb
 
 
-def check_gate(context: CouchersContext, gate_name: str) -> bool:
+def evaluate_boolean(context: CouchersContext, flag_key: str, default: bool) -> bool:
     """
-    Check if a feature gate is enabled for the user in this context.
+    Evaluate a boolean feature gate for the user in this context.
 
-    Returns False if experimentation is disabled, True if EXPERIMENTATION_PASS_ALL_GATES is set.
+    Mirrors OpenFeature's get_boolean_value. Returns True if EXPERIMENTATION_PASS_ALL_GATES
+    is set, the in-code default if experimentation is disabled or the flag isn't set up in
+    GrowthBook, otherwise the gate's value. Goes through get_feature_value (not is_on) so the
+    default is honored for not-yet-created flags.
     """
     _check_initialized()
     if config["EXPERIMENTATION_PASS_ALL_GATES"]:
         return True
     if not config["EXPERIMENTATION_ENABLED"]:
-        return False
-    return _get_growthbook(context).is_on(gate_name)
+        return default
+    return bool(_get_growthbook(context).get_feature_value(flag_key, default))
 
 
-def get_feature_value[T](context: CouchersContext, feature_name: str, default: T) -> T:
+def evaluate_value[T](context: CouchersContext, flag_key: str, default: T) -> T:
     """
-    Get the value of a feature for the user in this context.
+    Evaluate a non-boolean feature value for the user in this context.
 
-    Use this for non-boolean features: strings, numbers, dicts, experiment variations,
-    dynamic configs - anything other than a simple on/off gate. The default's type
-    determines the return type and is returned verbatim when experimentation is disabled.
+    Mirrors OpenFeature's get_string_value/get_integer_value/get_float_value/get_object_value.
+    The default's type determines the return type; it's returned verbatim when experimentation
+    is disabled or the flag isn't set up in GrowthBook.
     """
     _check_initialized()
     if not config["EXPERIMENTATION_ENABLED"]:
         return default
-    return _get_growthbook(context).get_feature_value(feature_name, default)  # type: ignore[no-any-return]
+    return _get_growthbook(context).get_feature_value(flag_key, default)  # type: ignore[no-any-return]

app/backend/src/couchers/servicers/account.py

@@ -27,7 +27,6 @@
     verify_token,
 )
 from couchers.event_log import log_event
-from couchers.experimentation import check_gate
 from couchers.helpers.completed_profile import has_completed_profile
 from couchers.helpers.geoip import geoip_approximate_location
 from couchers.helpers.strong_verification import get_strong_verification_fields
@@ -169,7 +168,7 @@ def GetAccountInfo(
 
         # Test experimentation integration - check if user is in the test gate
         # Create 'test_growthbook_integration' in GrowthBook to test
-        test_gate = check_gate(context, "test_growthbook_integration")
+        test_gate = context.get_boolean_value("test_growthbook_integration", default=False)
         logger.info(f"Experimentation gate 'test_growthbook_integration' for user {user.id}: {test_gate}")
 
         should_show_donation_banner = DONATION_DRIVE_START is not None and (

app/backend/src/couchers/sql.py

@@ -4,7 +4,6 @@
 from sqlalchemy.orm import InstrumentedAttribute, aliased
 from sqlalchemy.sql import Select, exists, union
 
-from couchers.context import CouchersContext
 from couchers.models import (
     ModerationState,
     ModerationVisibility,
@@ -16,6 +15,7 @@
 from couchers.utils import is_valid_email, is_valid_user_id, is_valid_username
 
 if TYPE_CHECKING:
+    from couchers.context import CouchersContext
     from couchers.materialized_views import LiteUser
     from couchers.models.moderation import ModeratedContent