Suppose that I ran cabal sandbox init .. cabal install -j some-package and got a build failure in one of dependencies of some-package. One way to solve this is I notify the author of the failure and then wait for them to release a new version, but the process can sometimes be too slow. When the reason of the failure is obvious (which is often the case,) I want to launch my text editor and fix it by myself.
However when I ran find(1) for the filename from the error log in .cabal-sandbox cache directory, I could find no .hs files. Does the cabal command remove the entire source directory when GHC successfully or unsuccessfully finishes its execution? How can I intrude into cabal's task executions? Or, are there any standardized way to achieve my original goal of fixing software packages from Hackage by myself?
You can download package source with cabal get <package> then fix it and install into sandbox with cabal install <package-dir>.
E.g.
$ cabal get split
Unpacking to split-0.2.2/
$ vim split-0.2.2/split.cabal
$ cabal install ./split-0.2.2