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from fluent.syntax import ast as FTL
from fluent.syntax.visitor import Transformer
from .transforms import Transform
class Evaluator(Transformer):
"""An AST transformer for evaluating migration Transforms.
An AST transformer (i.e. a visitor capable of modifying the AST) which
walks an AST hierarchy and evaluates nodes which are migration Transforms.
"""
def __init__(self, ctx):
self.ctx = ctx
def visit(self, node):
if not isinstance(node, FTL.BaseNode):
return node
if isinstance(node, Transform):
# Some transforms don't expect other transforms as children.
# Evaluate the children first.
transform = self.generic_visit(node)
# Then, evaluate this transform.
return transform(self.ctx)
return self.generic_visit(node)