Simple, hassle-free, dependency-free, AST based fragmental source code refactoring and transformation toolkit.
Our framework is primarily built on the principle of “simple but effective transformations”. We focus on refactorings that target a small span of source code, and work our way out from it. What this enables for us is being able to operate directly on a single format for both analyses and transformations. This is what we shine at compared to other similar tools.
Let’s not get into too much details, but just to give a sneak peek we
can try to write a rule that would replace the identifier
import ast from refactor import Rule, Replace, run # Each refactor transformer inherits from "refactor.Rule" class FillPlaceholders(Rule): # And each rule implements a "match()" method, which would # receive every node in the tree in a breadth-first order. def match(self, node: ast.AST) -> Replace: # This is where things get interesting. Instead of just writing # filters with if statements, you can use the following assert # based approach (a contract of transformation). # For this case, our contract is going to be: if the given node # is an identifier with the name of "placeholder", it will be # replaced with literal "42". assert isinstance(node, ast.Name) assert node.id == "placeholder" # And this is where we choose what action we are taking for the # given node (which we have verified with our contract). There # are multiple transformation actions, but in this case what we # need is something that replaces a node with another one. replacement = ast.Constant(42) return Replace(node, replacement) if __name__ == "__main__": # And finally in here, we just use the default CLI that comes # bundled with refactor. When provided with a bunch of rules, # it creates a simple interface that can process given files # show the diff for changes and even apply them. run(rules=[FillPlaceholders])
If we run the rule above on a file, we can see how it performs:
--- test_file.py +++ test_file.py @@ -1,11 +1,11 @@ def main(): - print(placeholder * 3 + 2) + print(42 * 3 + 2) - print(2 + placeholder + 3) + print(2 + 42 + 3) # some comments - placeholder # maybe other comments + 42 # maybe other comments if something: other_thing - print(placeholder) + print(42) if __name__ == "__main__": main()