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Source-location aware parser for package descriptions #1127

dag opened this Issue Nov 21, 2012 · 7 comments

7 participants

dag commented Nov 21, 2012

It would be nice if Cabal included a parser for .cabal files that remembers line and column numbers for parsed entities. This could then be used by tools like packdeps to give the source location for an outdated dependency, and in turn used in text editors to annotate lines with information from packdeps when editing a .cabal file.

More broadly, it would be nice to have an exact-printer for the relevant AST, to make it possible to write tools that process .cabal files programmatically without messing up their formatting.


This (an exact parser/printer) is something I would also like to see.

I may work on it eventually, but it's not high on my priority list.

Haskell member

It would be also nice to have the same for config files.

Haskell member
dcoutts commented Nov 12, 2013

I have a new parser (for .cabal files and config files). The only problem is it needs parsec which currently we cannot depend on because it causes problems for GHC. There is however a plan to get GHC to not depend on Cabal, or rather have the ghc lib not depend on Cabal, only ghc-pkg & the build system. This may allow us to depend on parsec and so we could have a fast and nice new parser.

dag commented Nov 12, 2013

A silly thought: is ReadP too weak for this?

Haskell member
dcoutts commented Nov 12, 2013

ReadP is what we use now. It's terrible. It has no error reporting and no source locations. It's also slow.

Haskell member
byorgey commented Nov 13, 2013

@dcoutts: Exciting! (A patient sort of excitement.)

Haskell member
erikd commented Dec 10, 2014

I understand why we can't currently use Parsec for tthis, but would it be possible to use alex and happy? Obviously not as elegant as Parsec but probably better than ReadP.

@ttuegel ttuegel added the library label Apr 23, 2015
@ttuegel ttuegel modified the milestone: _|_, Cabal-1.24 Apr 23, 2015
@23Skidoo 23Skidoo modified the milestone: Cabal 1.24, Cabal 1.26 Feb 21, 2016
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