Fix --program-{prefix,suffix} resulting in invalid installation

Currently the options `--program-{prefix,suffix}` for cabal install
affects the name of the file in the install directory *and* the
executable name in the store. The installation fails:

- If using `--install-method=symlink`, the *target* of the symlink is
  not affected by the affix options and it results in an invalid symlink.
- If using `--install-method=copy`, the copy fails because the source
  is not found.

Another issue is that it affects the computation of the hash of the
build directory in the store, resulting in needless rebuild when using
successively different affix options.

Fixed by making the name of the executable in the store canonical, i.e.
always ignoring the program affix options.

Added a test for all the combinations of `--install-method` and program
affixes options.

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

@@ -540,7 +540,7 @@ installAction flags@NixStyleFlags{extraFlags, configFlags, installFlags, project
         -- BuildOutcomes because we also need the component names
           traverseInstall (installCheckUnitExes InstallCheckInstall) installCfg
   where
-    configFlags' = disableTestsBenchsByDefault configFlags
+    configFlags' = disableTestsBenchsByDefault . ignoreProgramAffixes $ configFlags
     verbosity = fromFlagOrDefault normal (setupVerbosity $ configCommonFlags configFlags')
     ignoreProject = flagIgnoreProject projectFlags
     cliConfig =
@@ -1101,6 +1101,18 @@ disableTestsBenchsByDefault configFlags =
     , configBenchmarks = Flag False <> configBenchmarks configFlags
     }
 
+-- | Disables program prefix and suffix, in order to get the /canonical/
+-- executable name in the store and thus:
+--
+-- * avoid making the package hash depend on these options and needless rebuild;
+-- * provide the correct executable path to the install methods (copy, symlink).
+ignoreProgramAffixes :: ConfigFlags -> ConfigFlags
+ignoreProgramAffixes configFlags =
+  configFlags
+    { configProgPrefix = NoFlag
+    , configProgSuffix = NoFlag
+    }
+
 -- | Prepares a record containing the information needed to either symlink or
 -- copy an executable.
 symlink :: OverwritePolicy -> InstallExe -> UnitId -> UnqualComponentName -> Symlink

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

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

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

@@ -0,0 +1 @@
+packages: .

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

@@ -0,0 +1,27 @@
+import Test.Cabal.Prelude
+import Data.Foldable (traverse_)
+
+-- Test that program affixes options result in successful installation:
+-- • Valid symlinks (--install-method=symlink)
+-- • Valid copy of executables (--install-method=copy)
+main = cabalTest $ do
+  env <- getTestEnv
+  recordMode DoNotRecord $ do
+    let installdir = testPrefixDir env </> "bin"
+        commonOpts = ["p", "--installdir", installdir, "--overwrite-policy=always"]
+        testAllAffixes installMethod = do
+          let testAffixes' = testAffixes
+                (commonOpts ++ ["--install-method", installMethod])
+          testAffixes' Nothing Nothing
+          testAffixes' (Just "a-") Nothing
+          testAffixes' Nothing (Just "-z")
+          testAffixes' (Just "a-") (Just "-z")
+    traverse_ testAllAffixes ["symlink", "copy"]
+  where
+    mkAffixOption option = maybe [] (\a -> ["--program-" ++ option, a])
+    mkProgramName p s = maybe [] id p ++ "p" ++ maybe [] id s
+    testAffixes commonOpts prefix suffix = do
+      cabal "install" (  commonOpts
+                      ++ mkAffixOption "prefix" prefix
+                      ++ mkAffixOption "suffix" suffix)
+      runInstalledExe (mkProgramName prefix suffix) []

cabal-testsuite/PackageTests/Install/ProgramAffixes/p.cabal

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

changelog.d/issue-9919

@@ -0,0 +1,4 @@
+synopsis: Fix --program-suffix resulting in invalid installation
+packages: cabal-install
+issues: #8823 #9919
+prs: #10056