def _LookupValue(module, parent_kind, implied_kind, ast_leaf_node):
"""Resolves a leaf node in the form ('IDENTIFIER', 'x') to a constant value
identified by 'x' in some mojom definition. parent_kind is used as context
when resolving the identifier. If the given leaf node is not an IDENTIFIER
(e.g. already a constant value), it is returned as-is.
If implied_kind is provided, the parsed identifier may also be resolved within
its scope as fallback. This can be useful for more concise value references
when assigning enum-typed constants or field values."""
if not isinstance(ast_leaf_node,
tuple) or ast_leaf_node[0] != 'IDENTIFIER':
return ast_leaf_node
# First look for a known user-defined identifier to resolve this within the
# enclosing scope.
identifier = ast_leaf_node[1]
value = _LookupValueInScope(module, parent_kind, identifier)
if value:
return value
# Next look in the scope of implied_kind, if provided.
value = (implied_kind and implied_kind.module and _LookupValueInScope(
implied_kind.module, implied_kind, identifier))
if value:
return value
# Fall back on defined builtin symbols
if _IsBuiltinValue(identifier):
return mojom.BuiltinValue(identifier)
raise ValueError('Unknown identifier %s' % identifier)
def _FixupExpression(module, value, scope, kind):
"""Translates an IDENTIFIER into a built-in value or structured NamedValue
object."""
if isinstance(value, tuple) and value[0] == 'IDENTIFIER':
# Allow user defined values to shadow builtins.
result = _LookupValue(module.values, value[1], scope, kind)
if result:
if isinstance(result, tuple):
raise Exception('Unable to resolve expression: %r' % value[1])
return result
if _IsBuiltinValue(value[1]):
return mojom.BuiltinValue(value[1])
return value
