Fix cabal-install in the presence of extra-packages

Extra-packages listed in a cabal project are to be fetched from hackage,
and will be in memory as 'NamedPackages' rather than resolved to
'SpecificSourcePackage'.

On install, we need to make source-dists for all the specific source
packages, and fetch other packages from hackage. Since extra-packages
are already 'NamedPackages', we simply return them along the sdistize-d
specific source packages and the hackage source packages -- they will be
correctly fetched from Hackage from install.

Previously, cabal install <tgt> on a project with extra-packages would
fail because the branch of 'NamedPackage' for 'PackageSpecifier' was
simply unimplemented.

Fixes #8848

Author: alt-romes

cabal-install/src/Distribution/Client/CmdInstall.hs

@@ -469,8 +469,7 @@ installAction flags@NixStyleFlags{extraFlags, configFlags, installFlags, project
 
     -- check for targets already in env
     let getPackageName :: PackageSpecifier UnresolvedSourcePackage -> PackageName
-        getPackageName (NamedPackage pn _) = pn
-        getPackageName (SpecificSourcePackage (SourcePackage pkgId _ _ _)) = pkgName pkgId
+        getPackageName = pkgSpecifierTarget
         targetNames = S.fromList $ map getPackageName (pkgSpecs ++ uriSpecs)
         envNames = S.fromList $ map getPackageName envSpecs
         forceInstall = fromFlagOrDefault False $ installOverrideReinstall installFlags
@@ -796,7 +795,16 @@ getSpecsAndTargetSelectors verbosity reducedVerbosity sourcePkgDb targetSelector
           TarGzArchive
           (distSdistFile distDirLayout (packageId pkg))
           pkg
-      NamedPackage pkgName _ -> error $ "Got NamedPackage " ++ prettyShow pkgName
+      NamedPackage _ _ ->
+        -- This may happen if 'extra-packages' are listed in the project file.
+        -- We don't need to do extra work for NamedPackages since they will be
+        -- fetched from Hackage rather than locally 'sdistize'-d. Note how,
+        -- below, we already return the local 'sdistize'-d packages together
+        -- with the 'hackagePkgs' (which are 'NamedPackage's), and that
+        -- 'sdistize' is a no-op for 'NamedPackages', meaning the
+        -- 'NamedPackage's in 'localPkgs' will be treated just like
+        -- 'hackagePkgs' as they should.
+        pure ()
 
     if null targetsMap
       then return (hackagePkgs, hackageTargets)

cabal-testsuite/PackageTests/Install/T8848/Main.hs

@@ -0,0 +1 @@
+main = pure ()

cabal-testsuite/PackageTests/Install/T8848/cabal.project

@@ -0,0 +1,2 @@
+packages: .
+extra-packages: containers

cabal-testsuite/PackageTests/Install/T8848/cabal.test.hs

@@ -0,0 +1,5 @@
+import Test.Cabal.Prelude
+
+main = cabalTest $ do
+  cabal' "install" ["t8848"]
+    >>= assertOutputContains "Wrote tarball sdist to"

cabal-testsuite/PackageTests/Install/T8848/t8848.cabal

@@ -0,0 +1,8 @@
+name: t8848
+version: 1.0
+build-type: Simple
+cabal-version: >= 1.2
+
+executable t8848
+  main-is: Main.hs
+  build-depends: base