stack ghci doesn't load any files

[ndmitchell]

C:\Neil\hlint>stack --version
Version 0.0.3.1, Git revision e3b18221509a7609b9ab6124ced5294dec05c82a

C:\Neil\hlint>stack ghci
Configuring GHCi with the following packages: hlint
GHCi, version 7.8.4: http://www.haskell.org/ghc/  :? for help
Loading package ghc-prim ... linking ... done.
Loading package integer-gmp ... linking ... done.
Loading package base ... linking ... done.
Prelude> :show modules
Prelude>

I was expecting stack ghci to load the hlint library, but it doesn't, it loads nothing.

[ndmitchell]

btw, this is after deleting the .ghci file in the hlint repo, to replicate the "normal user" experience.

[chrisdone]

Related: #347 (comment)

tl;dr it's not supposed to load anything on start-up, but enough people want it that I'll make it do that by default and add --no-load flag for people like me who don't want it doing that by default.

[ndmitchell]

I don't super care about the default, since this is for using it through ghcid, but is there any way to replicate something close to what cabal repl does?

Also:

C:\Neil\hlint>stack ghci Sample.hs
Configuring GHCi with the following packages:
GHCi, version 7.8.4: http://www.haskell.org/ghc/  :? for help
Loading package ghc-prim ... linking ... done.
Loading package integer-gmp ... linking ... done.
Loading package base ... linking ... done.
Prelude>

I would have expected that to try loading Sample.hs.

[chrisdone]

This works: #328 (comment)

chris@retina:~/Work/stack$ stack ghci --ghc-options X.hs
Configuring GHCi with the following projects: stack
GHCi, version 7.8.4: http://www.haskell.org/ghc/  :? for help
Warning: -debug, -threaded and -ticky are ignored by GHCi
Loading package ghc-prim ... linking ... done.
Loading package integer-gmp ... linking ... done.
Loading package base ... linking ... done.
Ok, modules loaded: Main.
Prelude Main> 

But enough people have assumed stack ghci should run :load automatically on all target modules by default that it's planned for implementation.

[ndmitchell]

OK, I guess I'll hold off on integration until after things have settled down.

[ndmitchell]

@chrisdone - can you please update this ticket once you think stack is ready and isn't going to change significantly.

[chrisdone]

Sure.

[ndmitchell]

So currently for https://github.com/ndmitchell/hoogle stack ghci is loading all the "other-modules" in the executable, but not "Main". That seems a bit weird. Is that a known issue?

[chrisdone]

Yeah, as Main is ambiguous in the presence executables and test suites. But with the new target code one will be able to specify which targets to load to clarify this ambiguity.

[ndmitchell]

Is the first executable or test-suite in the module not a good default? That way people could reorder their cabal file to get what they are after.

[ndmitchell]

I should also note that I always name my executables and test suites differently and us -main-is, precisely so I can load them all simultaneously (and because that's how some other proprietary Haskell variants work, and seems much more sensible).

[chrisdone]

I imagine -main-is takes a filename? So it would be like stack ghci --main-is src/main/Main.hs to automatically load that module on start-up.

We could have it take a cabal component name instead in the interest of being convenient, e.g. -main-is exe:foo or -main-is test:foo.

[ndmitchell]

Yep, search for main-is here: https://github.com/ndmitchell/shake/blob/master/shake.cabal

[chrisdone]

What if you have a test suite named Main and an executable named Main? How would you want to distinguish them when calling stack ghci?

[ndmitchell]

I would have thought:

• Always load as many modules as you can while they don't overlap. e.g. If there is one Test and one Main, try loading both at once.
• The prompt should have active (e.g. imported into it) the first "thing" loaded, either a test suite or an executable, whatever is first in the .cabal file. If there are no test suites or executables, import all modules exposed.
• Let people pass the name of a test-suite or executable to refine the choice, e.g. for shake the executable is executable shake and the test suite is test-suite shake-test.

[chrisdone]

I've implemented this. If I load up stack ghci in lucid, I get:

The main module to load is ambiguous. Candidates are: 
Package `lucid' component test:test with main-is file: /home/chris/Packages/lucid/test/Main.hs
Package `lucid' component bench:bench with main-is file: /home/chris/Packages/lucid/benchmarks/Main.hs
None will be loaded. You can specify which one to pick by: 
 1) Specifying targets to stack ghci e.g. stack ghci lucid:test:test
 2) Specifying what the main is e.g. stack ghci --main-is lucid:test:test

So I can either just load the one target that I want, or I can proceed trying to load everything and specify what the main is.

[ndmitchell]

Awesome! Just tried this with HLint and it worked straight away.

[chrisdone]

Cool, closing.