refactor 0.3.0

AST based source code refactor interface

Refactor

Simple, hassle-free, dependency-free, AST based source code refactoring toolkit.

Why? How?

refactor is an end-to-end refactoring framework that is built on top of the 'simple but effective refactorings' assumption. It is much easier to write a simple script with it rather than trying to figure out what sort of a regex you need in order to replace a pattern (if it is even matchable with regexes).

Every refactoring rule offers a single entrypoint, match(), where they accept an AST node (from the ast module in the standard library) and respond with either returning an action to refactor or nothing. If the rule succeeds on the input, then the returned action will build a replacement node and refactor will simply replace the code segment that belong to the input with the new version.

Here is a complete script that will replace every placeholder access with 42 (not the definitions) on the given list of files:

import ast
from refactor import Rule, ReplacementAction, run

class Replace(Rule):
    
    def match(self, node):
        assert isinstance(node, ast.Name)
        assert node.id == 'placeholder'
        
        replacement = ast.Constant(42)
        return ReplacementAction(node, replacement)
        
if __name__ == "__main__":
    run(rules=[Replace])

If we run this on a file, refactor will print the diff by default;

--- test_file.py
+++ test_file.py

@@ -1,11 +1,11 @@

 def main():
-    print(placeholder * 3 + 2)
-    print(2 +               placeholder      + 3)
+    print(42 * 3 + 2)
+    print(2 +               42      + 3)
     # some commments
-    placeholder # maybe other comments
+    42 # maybe other comments
     if something:
         other_thing
-    print(placeholder)
+    print(42)
 
 if __name__ == "__main__":
     main()

As stated above, refactor's scope is usually small stuff, so if you want to do full program transformations we highly advise you to look at CST-based solutions like parso, LibCST and Fixit