ghc-pkg should drop trailing path separator when computing package database root

Reported on ghc-devs@,

Nicolas Dudebout <nicolas.dudebout@gmail.com> writes,

When passing a package database to ghc-pkg via GHC_PACKAGE_PATH or --package-db, ${pkgroot} does not get computed properly if the input path contains a trailing slash.

Default behavior:

$ ghc-pkg describe base | grep pkgroot
pkgroot: "/usr/lib/ghc-7.10.2"

Correct behavior (no trailing slash):

$ ghc-pkg --package-db /usr/lib/ghc-7.10.2/package.conf.d describe base
| grep pkgroot
pkgroot: "/usr/lib/ghc-7.10.2"

$ GHC_PACKAGE_PATH=/usr/lib/ghc-7.10.2/package.conf.d ghc-pkg describe
base | grep pkgroot
pkgroot: "/usr/lib/ghc-7.10.2"

Incorrect behavior (with trailing slash):

$ ghc-pkg --package-db /usr/lib/ghc-7.10.2/package.conf.d/ describe
base | grep pkgroot
pkgroot: "/usr/lib/ghc-7.10.2/package.conf.d"

$ GHC_PACKAGE_PATH=/usr/lib/ghc-7.10.2/package.conf.d/ ghc-pkg describe
base | grep pkgroot
pkgroot: "/usr/lib/ghc-7.10.2/package.conf.d"

When this bug happens, ghc-pkg check complains about missing files for packages using ${pkgroot}.

This bug happens because ${pkgroot} is computed using takeDirectory. It should instead use (takeDirectory . dropTrailingPathSeparator).

Trac metadata

Trac field	Value
Version	8.0.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Package system
Test case
Differential revisions
BlockedBy
Related
Blocking
CC	nicolas.dudebout@gmail.com
Operating system
Architecture