Visual Studio Haskell

1
Visual Studio / Haskell

• Simon Marlow
• Krasimir Angelov
• others

2
Background

• We all use a development environment of one kind
  or another
• Emacs
• Vi
• Notepad
• WinHugs

3
Existing Haskell IDEs

• Some of these have some Haskell support
• syntax colouring
• indentation (hard in Haskell!)
• jump to errors
• menu of top-level declarations
• jump to definition
• interactive compilation/evaluation
• display type of an identifier

4
Problems

• Language support tends to be unreliable, because
  these environments are not using a real Haskell
  front-end. eg. Colouring support in Emacs is
  really bad.
• Different language flavours Haskell98FFI,
  hierarchical modules, CPP, literate.
• Jumping to an error often misses (compilers dont
  have good source loc info).
• No real compile support
• Many, many, many more things an IDE can do

5
What were doing

• Integrating GHC with Visual Studio to make a
  decent Haskell IDE
• Specifying a programatic interface to GHC so that
  it can be re-used in other IDE-like contexts.

6
Background Visual Studio

• Development shell, with several language plugins
  VC, VC, VJ, VB.
• Very rich feature set
• Lots of support for language integration
• Projects multi-file applications/libraries
• Solutions multiple projects
• Debugging
• Integrated documentation, context-sensitive help
  etc.
• Lots of support for automation/extension/customisa
  tion.
• free access to the integration APIs
• Windows only

7
Status of Haskell Plugin

• We have
• Syntax colouring
• Parsing/renaming/type-checking as you type (in a
  separate thread)
• accurate indication of erroneous subexpressions
• beginnings of project support

8
Demo
9
Features we want

• (in rough order of increasing difficulty)
• Bracket matching (inc. let/in)
• Drop-down menu of top-level decls
• Outlining
• Jump to definition (or docs for library fns)
• Easy access to documentation
• Code model (programatic access to the source code
  from a macro)
• Type tooltips
• Type of subexpression

10
More features we want

• Integrate with HaRe
• Project support
• Multi-module support (automatically discover
  dependencies, build support etc.)
• Library-infrastructure support (import/export
  library infrastructure metadata gives a nice way
  to package ship a project)
• Auto-Haddocking for a project
• Integrated FFI tools??
• .NET integration??
• Debugging??
• GUI Builder??

11
Implementation

• Visual Studio Integration Program
• set of COM APIs for integrating new functionality
  into VS
• Language support in the editor
• Project
• Tools
• freely available SDK
• APIs are highly detailed, flexible HUGE
• Babel (Daan Leijen) provides a simpler
  abstraction layer for integrating simple language
  support

12
The obligatory block diagram
VSIP COM interfaces
Babel COM interfaces
Visual Studio
Babel
Haskell Service
C/C
Haskell
Direct to VSIP for project support
13
What weve done so far

• Infrastructure
• Use H/Direct for accessing COM APIs (about 15
  bugs in H/Direct found so far!)
• Multi-threading support in GHCs RTS (parsing
  colouring run in separate OS threads)
• Accurate source location info in GHCs internal
  abstract syntax (phew)
• Support in GHC to build GHC as a package
• Krasimir basic project support, more to come

14
GHC as a library

• What interface should GHC export?
• Needs to support these front-ends
• GHCi
• --make
• -e
• Visual Studio
• others
• Tell me what you need

15
Conclusion

• What features would you like to see in an IDE?
  What would make it compelling enough for you to
  use?
• Well ship GHC as a package soon.
• VS plugin will be available at some point (help
  needed!)

16
GHCs API
data ModuleGraph ModSummary data ModSummary
- contains module name, location, imports data
CmState cmInit GhcMode -gt DynFlags -gt IO
CmState -- Stuff for -make, basic GHCi
operation cmDepAnal CmState -gt FilePath -gt
IO ModuleGraph cmLoad CmState -gt
ModuleGraph -gt IO (CmState, Bool,
String) cmUnload CmState -gt IO CmState --
Visual Studio -- - Project knows the
ModuleGraph -- - Dont need to fully compile
modules data ErrMsg cmAnalyse CmState -gt
ModuleGraph -gt Module -gt IO (CmState,
Either ErrMsg ModuleInfo) cmModuleChanged
CmState gt Module -gt IO CmState
17
-- Should we provide access to the complete
abstract syntax -- (perhaps in a simplified form?
THSyntax? IfaceSyn?) or just -- accessors? data
SrcLoc data SrcSpan typeOfId SrcLoc -gt
ModuleInfo -gt Maybe Type defnOfId SrcLoc -gt
ModuleInfo -gt Maybe SrcLoc topDecls ModuleInfo
-gt (SrcSpan, String)