Stack ghci before stack build fails

[ndmitchell]

C:\Neil\hlint>stack ghci
Using main module: Package `hlint' component exe:hlint with main-is file: C:\Neil\hlint\src\Main.hs
Configuring GHCi with the following packages: hlint
GHCi, version 7.10.2: http://www.haskell.org/ghc/  :? for help

<command line>:
    Could not find module `Paths_hlint'
    Use -v to see a list of the files searched for.
Failed, modules loaded: none.
Prelude> :q
Leaving GHCi.

That's after deleting my .ghci file and removing my .stack-work.

My guess is stack ghci should generate the paths file if it needs it. I thought it used to do a whole build before launching ghci? Using 06a4b27.

[borsboom]

@chrisdone / @snoyberg: any thoughts?

[snoyberg]

That Paths module will have to be generated by Cabal, which unfortunately only happens from a call to build. I'm not deeply involved in the GHCi stuff, but it seems like a large number of issues are coming out of trying to avoid doing a full build before stack ghci starts, but that we just need to bite the bullet and do such a build anyway.

[chrisdone]

Yep, I agree. It's time to just bite the bullet and do the build and cache-and-ignore any exceptions to retain the optimistic case of running ghci. I was thinking we could also add a trivial --no-build flag for impatient people like myself.

[borsboom]

@chrisdone: currently stack targets and stack ide also both do an implicit build --only-dependencies beforehand and fail if that fails (since they use ghciSetup as well). Should their behaviour also be changed to match stack ghci's new behaviour?