cabal-install-solver: fix pkgconf 1.9 --modversion regression

Check that the numbers of *versions* output is equal to the number of pkgconf's

fixes #8923

The pkgconf behavior was reverted upstream in 2.0

(this should cover the case too of checking that equal pkgList lines are output also)

(cherry picked from commit 3832bea)

# Conflicts:
#	cabal-install-solver/src/Distribution/Solver/Types/PkgConfigDb.hs

cabal-install-solver/src/Distribution/Solver/Types/PkgConfigDb.hs

@@ -67,15 +67,31 @@ readPkgConfigDb verbosity progdb = handle ioErrorHandler $ do
         -- The output of @pkg-config --list-all@ also includes a description
         -- for each package, which we do not need.
         let pkgNames = map (takeWhile (not . isSpace)) pkgList
-        (pkgVersions, _errs, exitCode) <-
+        (outs, _errs, exitCode) <-
                      getProgramInvocationOutputAndErrors verbosity
                        (programInvocation pkgConfig ("--modversion" : pkgNames))
+<<<<<<< HEAD
         case exitCode of
           ExitSuccess -> (return . pkgConfigDbFromList . zip pkgNames) (lines pkgVersions)
           -- if there's a single broken pc file the above fails, so we fall back into calling it individually
           _ -> do
              info verbosity ("call to pkg-config --modversion on all packages failed. Falling back to querying pkg-config individually on each package")
              pkgConfigDbFromList . catMaybes <$> mapM (getIndividualVersion pkgConfig) pkgNames
+=======
+        let pkgVersions = lines outs
+        if exitCode == ExitSuccess && length pkgVersions == length pkgNames
+          then (return . pkgConfigDbFromList . zip pkgNames) pkgVersions
+          else
+          -- if there's a single broken pc file the above fails, so we fall back
+          -- into calling it individually
+          --
+          -- Also some implementations of @pkg-config@ do not provide more than
+          -- one package version, so if the returned list is shorter than the
+          -- requested one, we fall back to querying one by one.
+          do
+            info verbosity ("call to pkg-config --modversion on all packages failed. Falling back to querying pkg-config individually on each package")
+            pkgConfigDbFromList . catMaybes <$> mapM (getIndividualVersion pkgConfig) pkgNames
+>>>>>>> 3832beaf5 (cabal-install-solver: fix pkgconf 1.9 --modversion regression)
   where
     -- For when pkg-config invocation fails (possibly because of a
     -- too long command line).

changelog.d/pr-9391

@@ -0,0 +1,4 @@
+synopsis: fix pkgconfig-depends for pkgconf-1.9
+packages: cabal-install-solver
+prs: #9391
+issues: #8923