Add support to only compile script using stack shebang

[brandonchinn178]

I have a file

#!/usr/bin/env stack
{- stack script --resolver ... --package ... -}

and running ./Script.hs or stack Script.hs works as expected. But I would like to have a CI job checking that Script.hs builds (but not runs). I do see stack script has a --no-run flag, but it seems like I would have to copy the entire stack script command to do so:

stack script --compile --no-run Script.hs --resolver ... --package ...

Doing stack Script.hs --no-run or stack script Script.hs --no-run would fail; the first would pass --no-run as an argument to Script.hs, and the second would fail with "script requires --resolver".

The most straightforward way I see here is to add a STACK_INTERPRETER_NO_RUN=true env var that will add the --no-run flag to stack script and the appropriate flags to stack runghc.

[mpilgrem]

The current online help explains:

With the release of Stack 1.4.0, there is a new command, script, which will automatically:

• Install GHC and libraries if missing
• Require that all packages used be explicitly stated on the command line

This ensures that your scripts are independent of any prior deployment specific configuration, and are reliable by using exactly the same version of all packages every time it runs so that the script does not break by accidentally using incompatible package versions.

Rather than an environment variable, how about an additional flag for stack script that specifies that the script interepter options comment is to be used and not ignored (something like --use-options-comment) (disabled by default)?

[mpilgrem]

I thought further about this. I have a potential pull request that does the following: if new global flag --force-script-no-run-compile is enabled (disabled by default) it forces the options --no-run --compile on stack script.

So, for example, if you have a script Script.hs:

{- stack script
   --resolver lts-19.9
   --package acme-missiles
-}
import Acme.Missiles (launchMissiles)

main :: IO ()
main = launchMissiles

If you use:

 stack --force-script-no-run-compile Script.hs

then that gets translated (by stack, behind the scenes) into:

stack --force-script-no-run-compile script --resolver lts-19.9 --package acme-missiles -- Script.hs

which is then forced (by my pull request) to be the equivalent of having asked for:

stack script --resolver lts-19.9 --package acme-missiles --no-run --compile -- Script.hs

[mpilgrem]

The option - now named --script-no-run-compile - has been added to the current source code for stack.