_yaml: Add 'as_bool()' and 'is_none()' to ScalarNode

- 'as_bool()' casts a ScalarNode into a boolean, understanding both
  'True' and 'False' as truthy-falsy values, as per node_get(type=bool)
  behavior
- 'is_none()' allwos checking whether the scalar node contains a 'None'
  value. Since 'None' cannot be used when working with booleans, we need
  to have a way of checking for 'None' when we actually need the
  information of whether the value is unset.
- Adapt all call places to use the new API

1 files changed, 2 insertions, 2 deletions

diff --git a/src/buildstream/plugin.py b/src/buildstream/plugin.py
index a12ff61ec..e209e5f4e 100644
--- a/src/buildstream/plugin.py
+++ b/src/buildstream/plugin.py
@@ -894,10 +894,10 @@ class Plugin():
             project = self.__project
 
             for key, value in self.node_items(project.element_overrides):
-                if _yaml.node_get(value, bool, 'suppress-deprecation-warnings', default_value=False):
+                if value.get_bool('suppress-deprecation-warnings', default=False):
                     silenced_warnings.add(key)
             for key, value in self.node_items(project.source_overrides):
-                if _yaml.node_get(value, bool, 'suppress-deprecation-warnings', default_value=False):
+                if value.get_bool('suppress-deprecation-warnings', default=False):
                     silenced_warnings.add(key)
 
             return self.get_kind() in silenced_warnings