facebookarchive / Lex Pass

Archived Repo

This is an archived project and is no longer supported or updated by Facebook. Please do not file issues or pull-requests against this repo. If you wish to continue to develop this code yourself, we recommend you fork it.

Mailing list at: http://groups.google.com/group/lex-pass

lex-pass allows you to automate changes to a php codebase, by writing abstract-syntax-tree transformers in haskell. haskell is good because it is well-suited for language manipulation and because it has good parsing libraries that enable us to work with a nice abstract-syntax-tree.

to install

• ./install depends on
• futil (git://github.com/facebook/futil.git)

to use

• run lex-pass to see options
• to see an example run, run lex-pass example-global with a codebase in ~/www that uses some globals (e.g. "global $a;")
  • note a large codebase could takes tens of minutes the first run because no ast's are cached yet
  • you can ^C it early after it does 'Saving' on a few files to see how the changes work
• to write a new transformer
  • see src/Transf/ for examples
  • src/do-codegen (which is run by ./install) automatically detects new transformers in src/Transf/
• if you are using git you may want to use a separate repo instead of just a branch in an existing repo. files have mtime updated by branch-switching, so there will be some unnecessary re-parsing.

notes for those hacking on lex-pass itself

• todo
  • php: b'' type string literals
  • maintain cached asts for codebase somewhere so ppl don't have to wait on their first lex-pass run?
  • better error on one-arg transf's if args wrong?
  • better way to specify args in transf doc?
  • make showing full transf list an option instead of default help?
  • we might actually get better perf with our own lexer, or at least not restarting php over and over again to do lexing. but not worth looking into any time soon?
  • resolve xWs/xWS, xAst/xAST variable-capitalization indecision
  • future langs
    • css - easy and relevant, but maybe a css-preprocessor is better to use
    • js - relevant
    • bash (we should probably just stop using..), c, python