Consistently use the Cabal version picked by the dependency solver.

cabal-install/Distribution/Client/SetupWrapper.hs

@@ -106,7 +106,7 @@ import Control.Applicative ( (<$>), (<*>) )
 import Data.Monoid         ( mempty )
 #endif
 import Control.Monad       ( when, unless )
-import Data.List           ( foldl1' )
+import Data.List           ( find, foldl1' )
 import Data.Maybe          ( fromMaybe, isJust )
 import Data.Char           ( isSpace )
 import Distribution.Client.Compat.ExecutablePath  ( getExecutablePath )
@@ -389,26 +389,45 @@ externalSetupMethod verbosity options pkg bt mkargs = do
       Nothing    -> getInstalledPackages verbosity
                     comp (usePackageDB options') conf
 
-  cabalLibVersionToUse :: IO (Version, (Maybe ComponentId)
+  -- Choose the version of Cabal to use if the setup script has a dependency on
+  -- Cabal, and possibly update the setup script options. The version also
+  -- determines how to filter the flags to Setup.
+  --
+  -- We first check whether the dependency solver has specified a Cabal version.
+  -- If it has, we use the solver's version without looking at the installed
+  -- package index (See issue #3436). Otherwise, we pick the Cabal version by
+  -- checking 'useCabalSpecVersion', then the saved version, and finally the
+  -- versions available in the index.
+  --
+  -- The version chosen here must match the one used in 'compileSetupExecutable'
+  -- (See issue #3433).
+  cabalLibVersionToUse :: IO (Version, Maybe ComponentId
                              ,SetupScriptOptions)
   cabalLibVersionToUse =
-    case useCabalSpecVersion options of
-      Just version -> do
+    case find (hasCabal . snd) (useDependencies options) of
+      Just (unitId, pkgId) -> do
+        let version = pkgVersion pkgId
         updateSetupScript version bt
-        writeFile setupVersionFile (show version ++ "\n")
-        return (version, Nothing, options)
-      Nothing  -> do
-        savedVer <- savedVersion
-        case savedVer of
-          Just version | version `withinRange` useCabalVersion options
-            -> do updateSetupScript version bt
-                  -- Does the previously compiled setup executable still exist
-                  -- and is it up-to date?
-                  useExisting <- canUseExistingSetup version
-                  if useExisting
-                    then return (version, Nothing, options)
-                    else installedVersion
-          _ -> installedVersion
+        writeSetupVersionFile version
+        return (version, Just unitId, options)
+      Nothing ->
+        case useCabalSpecVersion options of
+          Just version -> do
+            updateSetupScript version bt
+            writeSetupVersionFile version
+            return (version, Nothing, options)
+          Nothing  -> do
+            savedVer <- savedVersion
+            case savedVer of
+              Just version | version `withinRange` useCabalVersion options
+                -> do updateSetupScript version bt
+                      -- Does the previously compiled setup executable still exist
+                      -- and is it up-to date?
+                      useExisting <- canUseExistingSetup version
+                      if useExisting
+                        then return (version, Nothing, options)
+                        else installedVersion
+              _ -> installedVersion
     where
       -- This check duplicates the checks in 'getCachedSetupExecutable' /
       -- 'compileSetupExecutable'. Unfortunately, we have to perform it twice
@@ -424,13 +443,20 @@ externalSetupMethod verbosity options pkg bt mkargs = do
           (&&) <$> setupProgFile `existsAndIsMoreRecentThan` setupHs
                <*> setupProgFile `existsAndIsMoreRecentThan` setupVersionFile
 
+      writeSetupVersionFile :: Version -> IO ()
+      writeSetupVersionFile version =
+          writeFile setupVersionFile (show version ++ "\n")
+
+      hasCabal (PackageIdentifier (PackageName "Cabal") _) = True
+      hasCabal _                                           = False
+
       installedVersion :: IO (Version, Maybe InstalledPackageId
                              ,SetupScriptOptions)
       installedVersion = do
         (comp,    conf,    options')  <- configureCompiler options
         (version, mipkgid, options'') <- installedCabalVersion options' comp conf
         updateSetupScript version bt
-        writeFile setupVersionFile (show version ++ "\n")
+        writeSetupVersionFile version
         return (version, mipkgid, options'')
 
       savedVersion :: IO (Maybe Version)

cabal-install/cabal-install.cabal

@@ -23,6 +23,19 @@ Extra-Source-Files:
   -- Do NOT edit this section manually; instead, run the script.
   -- BEGIN gen-extra-source-files
   tests/IntegrationTests/common.sh
+  tests/IntegrationTests/custom-setup/Cabal-99998/Cabal.cabal
+  tests/IntegrationTests/custom-setup/Cabal-99998/CabalMessage.hs
+  tests/IntegrationTests/custom-setup/Cabal-99999/Cabal.cabal
+  tests/IntegrationTests/custom-setup/Cabal-99999/CabalMessage.hs
+  tests/IntegrationTests/custom-setup/custom-setup-without-cabal-defaultMain/Setup.hs
+  tests/IntegrationTests/custom-setup/custom-setup-without-cabal-defaultMain/custom-setup-without-cabal-defaultMain.cabal
+  tests/IntegrationTests/custom-setup/custom-setup-without-cabal/Setup.hs
+  tests/IntegrationTests/custom-setup/custom-setup-without-cabal/custom-setup-without-cabal.cabal
+  tests/IntegrationTests/custom-setup/custom-setup/Setup.hs
+  tests/IntegrationTests/custom-setup/custom-setup/custom-setup.cabal
+  tests/IntegrationTests/custom-setup/custom_setup_without_Cabal_doesnt_allow_Cabal_import.sh
+  tests/IntegrationTests/custom-setup/custom_setup_without_Cabal_doesnt_require_Cabal.sh
+  tests/IntegrationTests/custom-setup/installs_Cabal_as_setup_dep.sh
   tests/IntegrationTests/custom/custom_dep.sh
   tests/IntegrationTests/custom/custom_dep/client/B.hs
   tests/IntegrationTests/custom/custom_dep/client/Setup.hs

cabal-install/tests/IntegrationTests/custom-setup/Cabal-99998/Cabal.cabal

@@ -0,0 +1,8 @@
+name: Cabal
+version: 99998
+build-type: Simple
+cabal-version: >= 1.2
+
+library
+  build-depends: base
+  exposed-modules: CabalMessage

cabal-install/tests/IntegrationTests/custom-setup/Cabal-99998/CabalMessage.hs

@@ -0,0 +1,3 @@
+module CabalMessage where
+
+message = "This is Cabal-99998"

cabal-install/tests/IntegrationTests/custom-setup/Cabal-99999/Cabal.cabal

@@ -0,0 +1,8 @@
+name: Cabal
+version: 99999
+build-type: Simple
+cabal-version: >= 1.2
+
+library
+  build-depends: base
+  exposed-modules: CabalMessage

cabal-install/tests/IntegrationTests/custom-setup/Cabal-99999/CabalMessage.hs

@@ -0,0 +1,3 @@
+module CabalMessage where
+
+message = "This is Cabal-99999"

cabal-install/tests/IntegrationTests/custom-setup/custom-setup-without-cabal-defaultMain/Setup.hs

@@ -0,0 +1,3 @@
+import Distribution.Simple
+
+main = defaultMain

cabal-install/tests/IntegrationTests/custom-setup/custom-setup-without-cabal-defaultMain/custom-setup-without-cabal-defaultMain.cabal

@@ -0,0 +1,9 @@
+name: custom-setup-without-cabal-defaultMain
+version: 1.0
+build-type: Custom
+cabal-version: >= 1.2
+
+custom-setup
+  setup-depends: base
+
+library

cabal-install/tests/IntegrationTests/custom-setup/custom-setup-without-cabal/Setup.hs

@@ -0,0 +1,4 @@
+import System.Exit
+import System.IO
+
+main = hPutStrLn stderr "My custom Setup" >> exitFailure

cabal-install/tests/IntegrationTests/custom-setup/custom-setup-without-cabal/custom-setup-without-cabal.cabal

@@ -0,0 +1,9 @@
+name: custom-setup-without-cabal
+version: 1.0
+build-type: Custom
+cabal-version: >= 99999
+
+custom-setup
+  setup-depends: base
+
+library

cabal-install/tests/IntegrationTests/custom-setup/custom-setup/Setup.hs

@@ -0,0 +1,5 @@
+import CabalMessage (message)
+import System.Exit
+import System.IO
+
+main = hPutStrLn stderr message >> exitFailure

cabal-install/tests/IntegrationTests/custom-setup/custom-setup/custom-setup.cabal

@@ -0,0 +1,9 @@
+name: custom-setup
+version: 1.0
+build-type: Custom
+cabal-version: >= 99999
+
+custom-setup
+  setup-depends: base, Cabal >= 99999
+
+library

cabal-install/tests/IntegrationTests/custom-setup/custom_setup_without_Cabal_doesnt_allow_Cabal_import.sh

@@ -0,0 +1,12 @@
+. ./common.sh
+cd custom-setup-without-cabal-defaultMain
+
+# This package has explicit setup dependencies that do not include Cabal.
+# Compilation should fail because Setup.hs imports Distribution.Simple.
+! cabal new-build custom-setup-without-cabal-defaultMain > output 2>&1
+cat output
+grep -q "\(Could not find module\|Failed to load interface for\).*Distribution\\.Simple" output \
+    || die "Should not have been able to import Cabal"
+
+grep -q "It is a member of the hidden package .*Cabal-" output \
+    || die "Cabal should be available"

cabal-install/tests/IntegrationTests/custom-setup/custom_setup_without_Cabal_doesnt_require_Cabal.sh

@@ -0,0 +1,11 @@
+. ./common.sh
+cd custom-setup-without-cabal
+
+# This package has explicit setup dependencies that do not include Cabal.
+# new-build should try to build it, even though the cabal-version cannot be
+# satisfied by an installed version of Cabal (cabal-version: >= 99999). However,
+# configure should fail because Setup.hs just prints an error message and exits.
+! cabal new-build custom-setup-without-cabal > output 2>&1
+cat output
+grep -q "My custom Setup" output \
+    || die "Expected output from custom Setup"

cabal-install/tests/IntegrationTests/custom-setup/installs_Cabal_as_setup_dep.sh

@@ -0,0 +1,15 @@
+# Regression test for issue #3436
+
+. ./common.sh
+cabal sandbox init
+cabal install ./Cabal-99998
+cabal sandbox add-source Cabal-99999
+
+# Install custom-setup, which has a setup dependency on Cabal-99999.
+# cabal should build the setup script with Cabal-99999, but then
+# configure should fail because Setup just prints an error message
+# imported from Cabal and exits.
+! cabal install custom-setup/ > output 2>&1
+
+cat output
+grep -q "This is Cabal-99999" output || die "Expected output from Cabal-99999"