[Haskell-cafe] ANN: HaRe 0.8 - The Haskell Refactorer

[Alan & Kim Zimmerman]

I'm pleased to announce the release of HaRe 0.8, available on hackage [1]

What's new?
===========

Everything, and nothing.

Everything in the sense that it has been completely reworked internally to make
use of the new API Annotations [2] in GHC 7.10.2, via the ghc-exactprint [3]
library.

Nothing in the sense that the functionality in this version is/should be
identical to that in 0.7.2.8

Limitations
===========

HaRe 0.8 will only work for projects using GHC 7.10.2 for compilation. Compiling
HaRe with 7.10.2 and then using it against projects using an earlier compiler
will not work, as HaRe needs to be able to invoke GHC to the type checker stage
on the project using GHC 7.10.2.

What is it?
===========

HaRe makes changes to working code, so that it still works once the change is
made.

Refactorings it can do are

* demote

  Take a declaration from the level where it is defined and move it down to the
  place where it is used. This only works if it is used in one place only.

* dupdef

  Duplicate a definition with a new name.

* iftocase

  Convert an if declaration to a case declaration.

* liftOneLevel

  Move a declaration one level up, adding parameters as needed to pass in
  locally declared variables.

* liftToTopLevel

  Move a declaration to the top level, adding parameters as needed to pass in
  locally declared variables.

* rename

  Change a name throughout the project. This makes use of the GHC renamed source
  so will not change other names that just happen to be lexically identical, but
  are in fact different names.

It currently has an emacs integration only, assistance in supporting other
environnments welcome.

[1] https://hackage.haskell.org/package/HaRe
[2] https://ghc.haskell.org/trac/ghc/wiki/ApiAnnotations
[3] https://hackage.haskell.org/package/ghc-exactprint

Alan

[Andrew Gibiansky]

Alan,

This is awesome. I can't express how excited I am to see this develop further.

I'll gladly start working on Vim support.

Could you describe how it works with emacs?

-- Andrew

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[Alan & Kim Zimmerman]

Hi Andrew

Thanks for the offer, that will be awesome.

In emacs the process is to highlight in a buffer the point where a change should happen, for example place the cursor on something that needs renaming, and then press the key binding for the relevant refactoring. The elisp uses the name of the buffer, location of the cursor and/or current highlighted region to construct the parameters for a call to ghc-hare.

When it is done, ghc-hare returns either (ok [files]) to indicate success and the names of the files that were changed, or (error "description of error").

HaRe does not actually change any files, it just places a new version next to to it with an extension of .refactored.hs. In emacs a (optional) series of ediff buffers are presented to review the changes. If the user accepts them the elisp copies the original files to the same name but with a date-time string as a suffix, and renames the refactored file to be the original. It should then reload the buffer, but I think that is missing right now.

Alan

[Simon Thompson]

Alan, Andrew,

The original version of HaRe did integrate with vim. This work was done more than 10 years ago, and it may well be that the mechanisms have changed. Still, the code should be in the HaRe repo. On the other hand, may be easier to start from scratch.

Kind regards, and great to hear that you’re planning to do this!

Simon T.

Simon Thompson | Professor of Logic and Computation 
School of Computing | University of Kent | Canterbury, CT2 7NF, UK
s.j.th...@kent.ac.uk | M +44 7986 085754 | W www.cs.kent.ac.uk/~sjt

[Marcin Mrotek]

Hello,

As for vim integration, neovim and
https://github.com/neovimhaskell/nvim-hs might be the way to go.

Best regards,
Marcin Mrotek

[Alan & Kim Zimmerman]

It is here: https://github.com/alanz/HaRe/tree/master/old/editors/Vim

[Alan & Kim Zimmerman]

Update: Version 0.8.1 is out, which fixes renaming that crosses module boundaries and preserves CPP directives