Add behavior flags to jinja context (#306)

dbt/adapters/base/impl.py

@@ -55,7 +55,7 @@
     BaseConnectionManager,
     Connection,
 )
-from dbt.adapters.base.meta import AdapterMeta, available
+from dbt.adapters.base.meta import AdapterMeta, available, available_property
 from dbt.adapters.base.relation import (
     BaseRelation,
     ComponentName,
@@ -272,7 +272,8 @@ def __init__(self, config, mp_context: SpawnContext) -> None:
         self.connections = self.ConnectionManager(config, mp_context)
         self._macro_resolver: Optional[MacroResolverProtocol] = None
         self._macro_context_generator: Optional[MacroContextGeneratorCallable] = None
-        self.behavior = []  # this will be updated to include global behavior flags once they exist
+        # this will be updated to include global behavior flags once they exist
+        self.behavior = []  # type: ignore
 
     ###
     # Methods to set / access a macro resolver
@@ -293,11 +294,11 @@ def set_macro_context_generator(
     ) -> None:
         self._macro_context_generator = macro_context_generator
 
-    @property
+    @available_property
     def behavior(self) -> Behavior:
         return self._behavior
 
-    @behavior.setter
+    @behavior.setter  # type: ignore
     def behavior(self, flags: List[BehaviorFlag]) -> None:
         flags.extend(self._behavior_flags)
         try:

dbt/adapters/base/meta.py

@@ -92,6 +92,25 @@ def parse_list(self, func: Callable) -> Callable:
 available = _Available()
 
 
+class available_property(property):
+    """
+    This supports making dynamic properties (`@property`) available in the jinja context.
+
+    We use `@available` to make methods available in the jinja context, but this mechanism relies on the method being callable.
+    Intuitively, we should be able to use both `@available` and `@property` to create a dynamic property that's available in the jinja context.
+
+    Using the `@property` decorator as the inner decorator supplies `@available` with something that is not callable.
+    Instead of returning the method, `@property` returns the value itself, not the method that is called to create the value.
+
+    Using the `@available` decorator as the inner decorator adds `_is_available_ = True` to the function.
+    However, when the `@property` decorator executes, it returns a `property` object which does not have the `_is_available_` attribute.
+
+    This decorator solves this problem by simply adding `_is_available_ = True` as an attribute on the `property` built-in.
+    """
+
+    _is_available_ = True
+
+
 class AdapterMeta(abc.ABCMeta):
     _available_: FrozenSet[str]
     _parse_replacements_: Dict[str, Callable]