AST based refactoring tool for and written in Python. (Pretty early days, somewhat usable.)

breakfast tries to refuse to guess in the face of ambiguity, so it should leave code that it doesn't fully understand alone, but I would definitely recommend using it only on code that is under version control, and make sure to inspect the diffs it produces.

(Neo)Vim is the editor I'm using, so my focus is to be able to use breakfast as a plugin there. Having said that, there is almost no vim specific code in this repository, other than what is needed to be able to install the project as a plugin from Github. Everything is implemented as an LSP server, and thus should work with other editors and IDEs that support that protocol.

I use Linux as my operating system of choice, and while I have tried hard to not make too many assumptions about the OS, it's likely that you'll encounter some issues if you try to use this project on Windows. I'll happily accept bug reports and patches, and suggestions on how to improve testing that will make stronger guarantees there.

...

Based in part on the amazing work done on Scope Graphs/Stack Graphs by Eelco Visser, Hendrik van Antwerpen, Douglas Creager, and others. (Though none of these people are responsible for/involved in this project or even aware it exists.)

It's likely that my implementation is naive or incorrect in places, and I've certainly resorted to some hacks to deal with things I couldn't figure out how to handle in the papers and presentations I found online. 1

Douglas Creager's excellent Strangeloop talk in particular, is what inspired me to switch to using Stack Graphs in this project. Even if you have no interest in using breakfast, I highly recommend his presentation.

Links:

• https://www.youtube.com/watch?v=l2R1PTGcwrE
• https://pl.ewi.tudelft.nl/research/projects/scope-graphs/

I've included some graphviz code to assist in debugging which renders scope graphs in a similar way to the one used in the presentation.The result is much uglier, but worked for its intended purpose.

1. I don't know if it's the most important, but it's a good meal. Also it has AST in it.
2. breakfast and move things > move fast and break things

To run tests:

make test

For instance, how to handle redefinition of variables in Python, in in code like:

a = 0  # global (unrelated) assignment
def fun():
    a = 1  # local assignment
    ...
    a = 2  # reassignment

One choice would be to view these as separate definitions, which would require separate rename refactorings. (And rewriting of statements like a += n.) My solution is to add occurrence (push) nodes for definitions that will look back for earlier definitions (only) in the same scope, but don't require any to be found: