Concat arguments when enabling haddock (#10783)

* Concat arguments when enabling haddock

Arguments were unioned with <> which is left-biased, therefore -haddock
swallowed all other args as indeed described in #10782.

I think the bug was introduced by 80f0a65, which makes the expression
modified in this PR to be non-empty if documentation was enabled.

Fixes #10782

* Add test for #10783 (concatenate arguments when enabling haddock)

---------

Co-authored-by: Matthew Pickering <matthewtpickering@gmail.com>
Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

Author: 3 people

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

cabal-testsuite/PackageTests/HaddockArgsCombine/CHANGELOG.md

@@ -0,0 +1,5 @@
+# Revision history for HaddockArgsCombine
+
+## 0.1.0.0 -- YYYY-mm-dd
+
+* First version. Released on an unsuspecting world.

cabal-testsuite/PackageTests/HaddockArgsCombine/HaddockArgsCombine.cabal

@@ -0,0 +1,14 @@
+cabal-version:   3.14
+name:            HaddockArgsCombine
+version:         0.1.0.0
+license:         NONE
+author:          Matthew Pickering
+maintainer:      matthewtpickering@gmail.com
+build-type:      Simple
+extra-doc-files: CHANGELOG.md
+
+executable HaddockArgsCombine
+    main-is:          Main.hs
+    build-depends:    base
+    hs-source-dirs:   app
+    default-language: Haskell2010

cabal-testsuite/PackageTests/HaddockArgsCombine/app/Main.hs

@@ -0,0 +1,6 @@
+module Main where
+
+import Data.List
+
+main :: IO ()
+main = putStrLn "Hello, Haskell!"

cabal-testsuite/PackageTests/HaddockArgsCombine/cabal.out

@@ -0,0 +1,8 @@
+# cabal v2-run
+Resolving dependencies...
+Build profile: -w ghc-<GHCVER> -O1
+In order, the following will be built:
+ - HaddockArgsCombine-0.1.0.0 (exe:HaddockArgsCombine) (first run)
+Configuring executable 'HaddockArgsCombine' for HaddockArgsCombine-0.1.0.0...
+Preprocessing executable 'HaddockArgsCombine' for HaddockArgsCombine-0.1.0.0...
+Building executable 'HaddockArgsCombine' for HaddockArgsCombine-0.1.0.0...

cabal-testsuite/PackageTests/HaddockArgsCombine/cabal.test.hs

@@ -0,0 +1,3 @@
+import Test.Cabal.Prelude
+main = cabalTest $ do
+        fails $ cabal "v2-run" ["--ghc-options=-Wall -Werror", "--enable-documentation"]

changelog.d/pr-10783

@@ -0,0 +1,11 @@
+synopsis: GHC arguments are no longer swallowed by enabling documentation
+packages: Cabal
+prs: #10783
+issues: #10782
+significance: significant
+
+description: {
+
+- Arguments to GHC are now properly concatenated with `-haddock` if documentation is enabled.
+
+}