This is a small update to just let people know what I’ve been up to. This will be a non-technical post.
There are 3 components which I want to get done before I put any code publicly online.
- Cabal support (being able to build and run Haskell projects from the IDE)
- Documentation support (class browser, quickinfo docs and F1 help integration along with jump to definition)
- Intellisense support
Of the 3 I want to get Cabal support working, then release something, get feedback while I work on the other two. I’m working on all 3 concurrently (mostly depending on which part of visual studio I want to mess with that day) So how far along are they.
- Cabal: I had a first version which hooked into the Cabal library and using quite a bit of reflection hacks and code changes to the MPF templates managed to load .cabal project files. This first approach was because I wanted to talk directly to Cabal, and not go through any intermediate layers. The reflection hacks were needed because the MPF templates are hardcoded to MSBuild, which uses an XML file format. Not using MPF would mean writing all that code myself which would have taken ages. Unfortunately this only worked sometimes, other times I would get an exception from deep within visual studio. I also had no idea how I would get building to work.
Ultimately I decided to scrap the entire approach al together, It wasn’t worth the hassle and would be hard to maintain. I’ve now settled on the idea of converting .Cabal files to an internal MSBuild script (and back to .cabal when saving), while adding new templates for a Haskell target type which just invokes cabal-install. This is a much simpler approach which takes some of the burden of maintenance of me and into other tools, but which unfortunately requires me to learn about MSBuild. Currently I’m creating the conversion tool Cabal2MSBuild, which is about 20% done.
- Documentation support: Documentation from the current module is gained from the AST inside GHC (hopefully, haven’t checked the data I get back yet). Documentation on external modules (e.g. package modules) are gained from two places (hopefully). For quick info the intellisense cache will be used, for class browser (e.g. browing of current project and dependencies) the .hpi files will be used. For F1 help haddock generated documentation will be used.
However in order for the haddock documentation to be integrated into visual studio it has to be in the correct format. As it turns out, documentation has been greatly simplified in visual studio 2010. The documentation format basically comes down to a zip files renamed to something else, which contains a simple index xml file and just xhtml content files. Great news there, since haddock already does generate xhtml. However I still need to modify the files generated to include a few meta tags, which will be used by the document installer to create indices of the html files, and for F1. I’ve started the modifications to Haddock and they’re about 60% done.
- Intellisense: I already have the .hpi files, which were those simplified indices of packages. I would like to provide intellisense for both project files and standalone Haskell files. There are a few ways to approach this. From what I’ve seen in the past, visual studio builds a intellisense cache file from the project dependencies on the fly on first launch/use of the project. If you have a large package database this could be handy, it limits the search space, but features such as auto-add imports/dependencies will become harder, as I would have to do 2 checks (local cache, and if not found hit a global cache). Standalone files also require me to only use the bigger (slower) global cache.
However the speed of that global cache hasn’t been measured yet (because the cache hasn’t been made yet) . So for now, until I have some hard numbers, I’ve settled on just always using the globally constructed index. This is also about 20-30% done. The majority of the work left is reading some documentation and papers.
Hopefully this informs you what I’ve been up to the past few weeks,
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