def construct_env_tag(loader: yaml.Loader, node: yaml.Node) -> Any:
"""Assign value of ENV variable referenced at node."""
default = None
if isinstance(node, yaml.nodes.ScalarNode):
vars = [loader.construct_scalar(node)]
elif isinstance(node, yaml.nodes.SequenceNode):
child_nodes = node.value
if len(child_nodes) > 1:
# default is resolved using YAML's (implicit) types.
default = loader.construct_object(child_nodes[-1])
child_nodes = child_nodes[:-1]
# Env Vars are resolved as string values, ignoring (implicit) types.
vars = [loader.construct_scalar(child) for child in child_nodes]
else:
raise yaml.constructor.ConstructorError(
None, None,
f'expected a scalar or sequence node, but found {node.id}',
node.start_mark)
for var in vars:
if var in os.environ:
value = os.environ[var]
# Resolve value to Python type using YAML's implicit resolvers
tag = loader.resolve(yaml.nodes.ScalarNode, value, (True, False))
return loader.construct_object(yaml.nodes.ScalarNode(tag, value))
return default
def no_duplicates_constructor(loader: yaml.Loader,
node: yaml.Node,
deep: bool = False) -> Any:
mapping: Dict[str, Any] = {}
for key_node, value_node in node.value:
key = loader.construct_object(key_node, deep=deep)
value = loader.construct_object(value_node, deep=deep)
if key in mapping:
raise yaml.constructor.ConstructorError(
"while constructing a mapping",
node.start_mark,
f"found duplicate key {key}",
key_node.start_mark,
)
mapping[key] = value
return loader.construct_mapping(node, deep)