Hooks: use the appropriate Cabal unit ID

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

@@ -1,4 +1,5 @@
 -----------------------------------------------------------------------------
+{-# LANGUAGE LambdaCase #-}
 
 -----------------------------------------------------------------------------
 
@@ -637,26 +638,52 @@ addDefaultSetupDependencies defaultSetupDeps params =
               { PD.packageDescription =
                   pkgdesc
                     { PD.setupBuildInfo =
-                        case PD.setupBuildInfo pkgdesc of
-                          Just sbi -> Just sbi
-                          Nothing -> case defaultSetupDeps srcpkg of
-                            Nothing -> Nothing
-                            Just deps
-                              | isCustom ->
-                                  Just
-                                    PD.SetupBuildInfo
-                                      { PD.defaultSetupDepends = True
-                                      , PD.setupDepends = deps
-                                      }
-                              | otherwise -> Nothing
+                        applyDefaultSetupBuildInfo
+                          (PD.setupBuildInfo pkgdesc)
                     }
               }
         }
       where
-        isCustom = PD.buildType pkgdesc == PD.Custom || PD.buildType pkgdesc == PD.Hooks
+        mbSetupDeps = defaultSetupDeps srcpkg
         gpkgdesc = srcpkgDescription srcpkg
         pkgdesc = PD.packageDescription gpkgdesc
 
+        applyDefaultSetupBuildInfo :: Maybe PD.SetupBuildInfo -> Maybe PD.SetupBuildInfo
+        applyDefaultSetupBuildInfo = \case
+          Just sbi
+            | PD.Hooks <- PD.buildType pkgdesc ->
+                -- Fix for #11331; see 'addCabalDepForHooks' for more details.
+                Just $ addCabalDepForHooks sbi
+          Nothing
+            | Just deps <- mbSetupDeps
+            , PD.buildType pkgdesc == PD.Custom || PD.buildType pkgdesc == PD.Hooks ->
+                Just $
+                  PD.SetupBuildInfo
+                    { PD.defaultSetupDepends = True
+                    , PD.setupDepends = deps
+                    }
+          mbSBI -> mbSBI
+
+-- | Add an implicit dependency on @Cabal@ for a @build-type: Hooks@ package
+-- that doesn't explicitly depend on @Cabal@. Rationale: we need the @Cabal@
+-- library in order to compile @main = defaultMainWithSetupHooks setupHooks@.
+--
+-- This ensures the solver picks a consistent version of @Cabal@ when other
+-- packages in the @setup-depends@ stanza depend on @Cabal@.
+-- See https://github.com/haskell/cabal/issues/11331.
+--
+-- NB: don't do this for @build-type: Custom@, as it is possible for such
+-- packages to not depend on @Cabal@ at all (although basically unheard of
+-- in practice).
+addCabalDepForHooks :: PD.SetupBuildInfo -> PD.SetupBuildInfo
+addCabalDepForHooks sbi@(PD.SetupBuildInfo{PD.setupDepends = deps})
+  | any ((== cabalPkgName) . depPkgName) deps =
+      sbi
+  | otherwise =
+      sbi{PD.setupDepends = Dependency cabalPkgName anyVersion mainLibSet : deps}
+  where
+    cabalPkgName = mkPackageName "Cabal"
+
 -- | If a package has a custom setup then we need to add a setup-depends
 -- on Cabal.
 addSetupCabalMinVersionConstraint

cabal-testsuite/PackageTests/SetupHooks/T11331/Cabal-bad/Cabal.cabal

@@ -0,0 +1,6 @@
+cabal-version: 2.4
+name: Cabal
+version: 3.16.666.0
+library
+  default-language: Haskell2010
+  build-depends: stub == 0.1

cabal-testsuite/PackageTests/SetupHooks/T11331/Cabal-good/Cabal.cabal

@@ -0,0 +1,10 @@
+cabal-version: 2.4
+name: Cabal
+version: 3.16.777.0
+library
+  default-language: Haskell2010
+  build-depends: base, stub == 0.2
+  exposed-modules:
+    Distribution.Simple.SetupHooks
+    Distribution.Simple
+  hs-source-dirs: src

cabal-testsuite/PackageTests/SetupHooks/T11331/Cabal-good/src/Distribution/Simple.hs

@@ -0,0 +1,13 @@
+module Distribution.Simple ( defaultMainWithSetupHooks ) where
+
+import System.Exit ( exitFailure )
+import Distribution.Simple.SetupHooks ( SetupHooks )
+
+defaultMainWithSetupHooks :: SetupHooks -> IO ()
+defaultMainWithSetupHooks _ = do
+  putStrLn "Chosen GOOD Cabal"
+  exitFailure
+  -- NB: we call 'exitFailure' here so that cabal-install, who is invoking
+  -- this code thinking it is building the package, doesn't try to proceed
+  -- when actually we haven't done anything (e.g. try to read a package
+  -- description file).

cabal-testsuite/PackageTests/SetupHooks/T11331/Cabal-good/src/Distribution/Simple/SetupHooks.hs

@@ -0,0 +1,3 @@
+module Distribution.Simple.SetupHooks where
+
+data SetupHooks = SetupHooks

cabal-testsuite/PackageTests/SetupHooks/T11331/Setup.hs

@@ -0,0 +1,14 @@
+{-# LANGUAGE NoImplicitPrelude #-}
+
+module Main where
+
+-- Cabal
+import Distribution.Simple ( defaultMainWithSetupHooks )
+
+-- T11331
+import SetupHooks ( setupHooks )
+
+--------------------------------------------------------------------------------
+
+main :: IO ()
+main = defaultMainWithSetupHooks setupHooks

cabal-testsuite/PackageTests/SetupHooks/T11331/SetupHooks.hs

@@ -0,0 +1,4 @@
+module SetupHooks (setupHooks) where
+
+-- fancy-hooks
+import FancyHooks (setupHooks)

cabal-testsuite/PackageTests/SetupHooks/T11331/T11331.cabal

@@ -0,0 +1,18 @@
+cabal-version:       3.14
+name:                T11331
+version:             0.1.0.0
+synopsis:            Test for Cabal bug 11331
+license:             BSD-3-Clause
+author:              NA
+maintainer:          NA
+category:            Testing
+build-type:          Hooks
+
+custom-setup
+  setup-depends: fancy-hooks
+
+library
+  default-language: Haskell2010
+  build-depends: stub == 0.1
+
+-- See cabal.test.hs for explanation of this test.

cabal-testsuite/PackageTests/SetupHooks/T11331/cabal.project

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

cabal-testsuite/PackageTests/SetupHooks/T11331/cabal.test.hs

@@ -0,0 +1,56 @@
+import Test.Cabal.Prelude
+
+{- Test for https://github.com/haskell/cabal/issues/11331
+
+This test works by having a package database with two Cabal libraries in it,
+a good one (Cabal-good) and a poisoned one (Cabal-bad).
+
+Cabal-good depends on stub == 0.2 and Cabal-bad depends on stub == 0.1.
+
+Moreover, we have a fancy-hooks package in the package database, that has been
+built against Cabal-good.
+
+T11331 has the following Cabal file:
+
+  T11331.setup --> fancy-hooks
+  T11331.lib   --> stub == 0.1
+
+The test checks that, for the setup component, we correctly use Cabal-good
+and not Cabal-bad, as only Cabal-good is compatible with fancy-hooks (correct
+ABI hash of Cabal dependency).
+-}
+main :: IO ()
+main = cabalTest $ recordMode DoNotRecord $ withPackageDb $ do
+  -- Build good package set 'fancy-hooks -> Cabal-good -> stub-0.2' first.
+  withDirectory "stub-0.2" $ do
+    setup "configure" []
+    setup "build" []
+    setup "register" ["--inplace"]
+  withDirectory "Cabal-good" $ do
+    setup "configure" []
+    setup "build" []
+    setup "register" ["--inplace"]
+  withDirectory "fancy-hooks" $ do
+    setup "configure" []
+    setup "build" []
+    setup "register" ["--inplace"]
+
+  -- Now build bad package set 'Cabal-bad -> stub-0.1'.
+  withDirectory "stub-0.1" $ do
+    setup "configure" []
+    setup "build" []
+    setup "register" ["--inplace"]
+  withDirectory "Cabal-bad" $ do
+    setup "configure" []
+    setup "build" []
+    setup "register" ["--inplace"]
+
+  -- Now try to build 'T11331' with cabal-install, using the package database
+  -- that we carefully crafted above. This tests that cabal-install picks
+  --  'Cabal-good' for the setup component of 'T11331', otherwise we will fail.
+  dbDir <- testPackageDbDir <$> getTestEnv
+
+  -- This fails because the fake Cabal-good defaultMain doesn't do anything
+  -- except print "Chosen GOOD Cabal".
+  res <- fails $ cabal' "build" [ "--package-db=" ++ dbDir, "T11331" ]
+  assertOutputContains "Chosen GOOD Cabal" res

cabal-testsuite/PackageTests/SetupHooks/T11331/fancy-hooks/fancy-hooks.cabal

@@ -0,0 +1,8 @@
+cabal-version: 2.4
+name: fancy-hooks
+version: 1.0
+library
+  default-language: Haskell2010
+  build-depends: Cabal
+  exposed-modules: FancyHooks
+  hs-source-dirs: src

cabal-testsuite/PackageTests/SetupHooks/T11331/fancy-hooks/src/FancyHooks.hs

@@ -0,0 +1,8 @@
+{-# LANGUAGE NoImplicitPrelude #-}
+
+module FancyHooks ( setupHooks ) where
+
+import Distribution.Simple.SetupHooks ( SetupHooks(..) )
+
+setupHooks :: SetupHooks
+setupHooks = SetupHooks

cabal-testsuite/PackageTests/SetupHooks/T11331/stub-0.1/stub.cabal

@@ -0,0 +1,5 @@
+cabal-version: 2.4
+name: stub
+version: 0.1
+library
+  default-language: Haskell2010

cabal-testsuite/PackageTests/SetupHooks/T11331/stub-0.2/stub.cabal

@@ -0,0 +1,5 @@
+cabal-version: 2.4
+name: stub
+version: 0.2
+library
+  default-language: Haskell2010

changelog.d/pr-11429.md

@@ -0,0 +1,27 @@
+---
+synopsis: Ensure consistency of `Cabal` version for `SetupHooks`
+packages: [cabal-install]
+prs: 11429
+issues: 11331
+---
+
+When building a package with `build-type: Hooks`, we build an executable which
+is invoked during the build process to perform build steps. This executable
+needs to be linked against the `Cabal` library, therefore we now add a
+dependency on `Cabal` when solving dependencies for the setup stanza.
+
+This fixes a bug which resulted in the solver choosing two inconsistent versions
+of the `Cabal` library, avoiding strange error messages like:
+
+```
+SetupHooks.hs: error: [GHC-83865]
+    • Couldn't match expected type ‘Distribution.Verbosity.Verbosity’
+                  with actual type ‘Verbosity’
+      NB: ‘Distribution.Verbosity.Verbosity’
+            is defined in ‘Distribution.Verbosity’ in package ‘Cabal-3.16.0.0’
+          ‘Verbosity’
+            is defined in ‘Distribution.Verbosity’ in package ‘Cabal-3.16.0.0’
+```
+
+where the error is that there are two different unit IDs for `Cabal` being
+passed when compiling the `SetupHooks` module.