From 78637237596a1753ece88bbbf1e0fddf12c2dd58 Mon Sep 17 00:00:00 2001
From: Teo Camarasu <teofilcamarasu@gmail.com>
Date: Fri, 18 Sep 2026 12:15:42 +0100
Subject: [PATCH] cabal-install: drop confusing deprecated msgs for
 perfer-oldest/coverage

The prefer-oldest and library-coverage arguments have now been superceded by new ones.
We used deprecation messages that referred to the Cabal spec to communicate this,
but this is wrong and confusing.
cabal-install flags have nothing to do with the Cabal spec!

Resolves #12357
---
 .../Client/ProjectConfig/FieldGrammar.hs             |  3 ---
 .../PackageTests/Regression/T5213/cabal.out          |  2 --
 changelog.d/12357.md                                 | 12 ++++++++++++
 3 files changed, 12 insertions(+), 5 deletions(-)
 create mode 100644 changelog.d/12357.md

diff --git a/cabal-install/src/Distribution/Client/ProjectConfig/FieldGrammar.hs b/cabal-install/src/Distribution/Client/ProjectConfig/FieldGrammar.hs
index ac371aee2f5..9ba089bca17 100644
--- a/cabal-install/src/Distribution/Client/ProjectConfig/FieldGrammar.hs
+++ b/cabal-install/src/Distribution/Client/ProjectConfig/FieldGrammar.hs
@@ -11,7 +11,6 @@ module Distribution.Client.ProjectConfig.FieldGrammar
 import Data.Bool (bool)
 import qualified Data.ByteString.Char8 as BS
 import qualified Data.Set as Set
-import Distribution.CabalSpecVersion (CabalSpecVersion (..))
 import Distribution.Client.CmdInstall.ClientInstallFlags (clientInstallFlagsGrammar)
 import qualified Distribution.Client.ProjectConfig.Lens as L
 import Distribution.Client.ProjectConfig.Types (PackageConfig (..), ProjectConfig (..), ProjectConfigBuildOnly (..), ProjectConfigProvenance (..), ProjectConfigShared (..))
@@ -199,11 +198,9 @@ packageConfigCoverageGrammar =
   (<>)
     <$> optionalFieldDef "coverage" L.packageConfigCoverage mempty
     <*> optionalFieldDef "library-coverage" L.packageConfigCoverage mempty
-      ^^^ deprecatedSince CabalSpecV1_22 "Please use 'coverage' field instead."
 
 packageConfigPreferVersion :: ParsecFieldGrammar ProjectConfigShared (Flag PreferVersion)
 packageConfigPreferVersion =
   mappend . fmap (bool PreferInstalledOrLatest PreferOldest)
     <$> optionalFieldDef "prefer-oldest" L.projectConfigPreferOldest mempty
-      ^^^ deprecatedSince CabalSpecV3_20 "Please use 'prefer-version' field instead."
     <*> optionalFieldDef "prefer-version" L.projectConfigPreferVersion mempty
diff --git a/cabal-testsuite/PackageTests/Regression/T5213/cabal.out b/cabal-testsuite/PackageTests/Regression/T5213/cabal.out
index bcbb8421e34..fb0e7ad7a9a 100644
--- a/cabal-testsuite/PackageTests/Regression/T5213/cabal.out
+++ b/cabal-testsuite/PackageTests/Regression/T5213/cabal.out
@@ -1,6 +1,4 @@
 # cabal new-test
-Warnings found while parsing the project file, cabal.project:
- - cabal.project:4:3: The field "library-coverage" is deprecated in the Cabal specification version 1.22. Please use 'coverage' field instead.
 Resolving dependencies...
 Build profile: -w ghc-<GHCVER> -O1
 In order, the following will be built:
diff --git a/changelog.d/12357.md b/changelog.d/12357.md
new file mode 100644
index 00000000000..9c4c4e3b06e
--- /dev/null
+++ b/changelog.d/12357.md
@@ -0,0 +1,12 @@
+---
+synopsis: Drop deprecation warnings for library-coverage and prefer-version flags
+packages: [cabal-install]
+prs: 12080
+issues: 12357
+---
+
+The `library-coverage` and `prefer-version` flags of `cabal-install` were marked as deprecated with
+reference to versions of the unrelated `.cabal` format spec, which is confusing, so we have dropped these
+messages.
+These flags are deprecated and we will likely re-introduce deprecation messages
+when we have a better way to communicate that.