Concat arguments when enabling haddock

Author: jasagredo

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

@@ -2319,13 +2319,16 @@ elaborateInstallPlan
                 ]
                 <> perPkgOptionMapLast pkgid packageConfigProgramPaths
             elabProgramArgs =
-              Map.fromList
-                [ (programId prog, args)
-                | prog <- configuredPrograms compilerprogdb
-                , let args = programOverrideArgs $ addHaddockIfDocumentationEnabled prog
-                , not (null args)
-                ]
-                <> perPkgOptionMapMappend pkgid packageConfigProgramArgs
+              Map.unionWith
+                (++)
+                ( Map.fromList
+                    [ (programId prog, args)
+                    | prog <- configuredPrograms compilerprogdb
+                    , let args = programOverrideArgs $ addHaddockIfDocumentationEnabled prog
+                            , not (null args)
+                    ]
+                )
+                (perPkgOptionMapMappend pkgid packageConfigProgramArgs)
             elabProgramPathExtra = perPkgOptionNubList pkgid packageConfigProgramPathExtra
             elabConfigureScriptArgs = perPkgOptionList pkgid packageConfigConfigureArgs
             elabExtraLibDirs = perPkgOptionList pkgid packageConfigExtraLibDirs

changelog.d/pr-10783

@@ -0,0 +1,10 @@
+synopsis: GHC arguments are no longer swallowed by enabling documentation
+packages: Cabal
+prs: #10783
+issues: #10782
+
+description: {
+
+- Arguments to GHC are now properly concatenated with `-haddock` if documentation is enabled.
+
+}