From c21eef43140f62e37da46b71472fde5262b6da2b Mon Sep 17 00:00:00 2001
From: Jens Petersen <petersen@redhat.com>
Date: Fri, 3 Nov 2023 16:30:40 +0800
Subject: [PATCH] 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 3832beaf50b9ec7d07111ce0f673de95577f48a9)

# Conflicts:
#	cabal-install-solver/src/Distribution/Solver/Types/PkgConfigDb.hs
---
 .../Distribution/Solver/Types/PkgConfigDb.hs  | 21 ++++++++++++-------
 changelog.d/pr-9391                           |  4 ++++
 2 files changed, 18 insertions(+), 7 deletions(-)
 create mode 100644 changelog.d/pr-9391

diff --git a/cabal-install-solver/src/Distribution/Solver/Types/PkgConfigDb.hs b/cabal-install-solver/src/Distribution/Solver/Types/PkgConfigDb.hs
index 11e6da847f0..418f716c21c 100644
--- a/cabal-install-solver/src/Distribution/Solver/Types/PkgConfigDb.hs
+++ b/cabal-install-solver/src/Distribution/Solver/Types/PkgConfigDb.hs
@@ -67,15 +67,22 @@ 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))
-        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
   where
     -- For when pkg-config invocation fails (possibly because of a
     -- too long command line).
diff --git a/changelog.d/pr-9391 b/changelog.d/pr-9391
new file mode 100644
index 00000000000..517c94ed127
--- /dev/null
+++ b/changelog.d/pr-9391
@@ -0,0 +1,4 @@
+synopsis: fix pkgconfig-depends for pkgconf-1.9
+packages: cabal-install-solver
+prs: #9391
+issues: #8923