From 9a2384467ade392286b244b315c74979429137ab Mon Sep 17 00:00:00 2001
From: Tom Ellis <tom-git@jaguarpaw.co.uk>
Date: Thu, 17 Sep 2020 17:51:18 +0100
Subject: [PATCH] Provide slightly more information when there are multiple
 packages

Partially addresses https://github.com/haskell/cabal/issues/6197
---
 .../src/Distribution/Client/ProjectOrchestration.hs          | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/cabal-install/src/Distribution/Client/ProjectOrchestration.hs b/cabal-install/src/Distribution/Client/ProjectOrchestration.hs
index e5110b36fb8..76514322413 100644
--- a/cabal-install/src/Distribution/Client/ProjectOrchestration.hs
+++ b/cabal-install/src/Distribution/Client/ProjectOrchestration.hs
@@ -551,8 +551,9 @@ resolveTargets selectPackageTargets selectComponentTarget
       | otherwise
       = Left (TargetProblemNoSuchPackage pkgid)
 
-    checkTarget (TargetPackage _ _ _)
-      = error "TODO: add support for multiple packages in a directory"
+    checkTarget (TargetPackage _ pkgids _)
+      = error ("TODO: add support for multiple packages in a directory.  Got\n"
+              ++ unlines (map prettyShow pkgids))
       -- For the moment this error cannot happen here, because it gets
       -- detected when the package config is being constructed. This case
       -- will need handling properly when we do add support.