aleator / abortplugin

Stop compilation if the project violates an import and export whitelist

AbortPlugin

This GHC plugin allows compilation to abort with an error if any non-whitelisted extension, or import is used.

This is meant to be used on a Haskell course where student answers go through an automatic inspection before grading. The aim of the plugin is to stop the most obvious cheating attempts, such as passing easy recursion exercises by just import Data.List.

Usage

This is a ghc plugin. The general pattern of usage is to

1. Add AbortPlugin as a dependency to your project.

2. Create a limitations file in style of the the default one, which contains whitelists of allowed imports and modules.

3. Invoke GHC with

     ghc -- -Wall -fplugin=AbortPlugin -fplugin-opt=AbortPlugin:Limitations.dhall YourFile.hs    
   

Building limitation specifications

You can also use this plugin to extract the extensions and imports used by a particular source file. This is done by prefixing the limitations filename by +-sign. For example:

     ghc -- -Wall -fplugin=AbortPlugin -fplugin-opt=AbortPlugin:+Limitations.dhall YourFile.hs    

This will overwrite the limitations file if it exists.

Caveat Emptor

This does not provide compilation safety! GHC allows options such as -F -pgmF ./something_nasty which cannot be intercepted by a compiler plugin.

A modicum of compiler safety can be obtained by careful whitelisting of extensions and modules and checking that the source file nor any of it's transitive imports does not contain the string OPTIONS_GHC (or any upper/lowercase permutation of it).