commit a9f00ffe4908b7f55af938f5a85943859f1e7af4
Author: Mike Pilgrem <mpilgrem@users.noreply.github.com>
Date:   Fri Apr 1 01:54:03 2022 +0100

    Allow stack to build with lts-19.1 (GHC 9.0.2)
    
    Uses C pre-processor (CPP) directives to not disturb the existing code that builds with versions of GHC before 9.0.2.
    
    Tested by building stack on Windows 11. The built stack executable was, in turn, then tested by using it to build stack on Windows 11.

Index: b/src/Stack/Build.hs
===================================================================
--- a/src/Stack/Build.hs
+++ b/src/Stack/Build.hs
@@ -1,5 +1,6 @@
 {-# LANGUAGE NoImplicitPrelude #-}
 {-# LANGUAGE ConstraintKinds #-}
+{-# LANGUAGE CPP #-}
 {-# LANGUAGE DeriveDataTypeable #-}
 {-# LANGUAGE FlexibleContexts #-}
 {-# LANGUAGE OverloadedStrings #-}
@@ -19,7 +20,12 @@ module Stack.Build
 
 import           Stack.Prelude hiding (loadPackage)
 import           Data.Aeson (Value (Object, Array), (.=), object)
+#if MIN_VERSION_aeson(2,0,0)
+import qualified Data.Aeson.Key as Key
+import qualified Data.Aeson.KeyMap as KeyMap
+#else
 import qualified Data.HashMap.Strict as HM
+#endif
 import           Data.List ((\\), isPrefixOf)
 import           Data.List.Extra (groupSort)
 import qualified Data.List.NonEmpty as NE
@@ -293,7 +299,11 @@ queryBuildInfo selectors0 =
     select front (sel:sels) value =
         case value of
             Object o ->
+#if MIN_VERSION_aeson(2,0,0)
+                case KeyMap.lookup (Key.fromText sel) o of
+#else
                 case HM.lookup sel o of
+#endif
                     Nothing -> err "Selector not found"
                     Just value' -> cont value'
             Array v ->
@@ -328,7 +338,11 @@ rawBuildInfo = do
     wantedCompiler <- view $ wantedCompilerVersionL.to (utf8BuilderToText . display)
     actualCompiler <- view $ actualCompilerVersionL.to compilerVersionText
     return $ object
+#if MIN_VERSION_aeson(2,0,0)
+        [ "locals" .= Object (KeyMap.fromList $ map localToPair locals)
+#else
         [ "locals" .= Object (HM.fromList $ map localToPair locals)
+#endif
         , "compiler" .= object
             [ "wanted" .= wantedCompiler
             , "actual" .= actualCompiler
@@ -336,7 +350,11 @@ rawBuildInfo = do
         ]
   where
     localToPair lp =
+#if MIN_VERSION_aeson(2,0,0)
+        (Key.fromText $ T.pack $ packageNameString $ packageName p, value)
+#else
         (T.pack $ packageNameString $ packageName p, value)
+#endif
       where
         p = lpPackage lp
         value = object
@@ -358,7 +376,11 @@ checkComponentsBuildable lps =
 checkSubLibraryDependencies :: HasLogFunc env => [ProjectPackage] -> RIO env ()
 checkSubLibraryDependencies proj = do
   forM_ proj $ \p -> do
+#if MIN_VERSION_Cabal(3,4,0)
+    C.GenericPackageDescription _ _ _ lib subLibs foreignLibs exes tests benches <- liftIO $ cpGPD . ppCommon $ p
+#else
     C.GenericPackageDescription _ _ lib subLibs foreignLibs exes tests benches <- liftIO $ cpGPD . ppCommon $ p
+#endif
 
     let dependencies = concatMap getDeps subLibs <>
                        concatMap getDeps foreignLibs <>
@@ -372,7 +394,7 @@ checkSubLibraryDependencies proj = do
       (logWarn "SubLibrary dependency is not supported, this will almost certainly fail")
   where
     getDeps (_, C.CondNode _ dep _) = dep
-    subLibDepExist lib = 
+    subLibDepExist lib =
       any (\x ->
         case x of
           C.LSubLibName _ -> True
Index: b/src/Stack/Build/Execute.hs
===================================================================
--- a/src/Stack/Build/Execute.hs
+++ b/src/Stack/Build/Execute.hs
@@ -1,5 +1,6 @@
 {-# LANGUAGE NoImplicitPrelude #-}
 {-# LANGUAGE ConstraintKinds       #-}
+{-# LANGUAGE CPP                   #-}
 {-# LANGUAGE DataKinds             #-}
 {-# LANGUAGE FlexibleContexts      #-}
 {-# LANGUAGE MultiParamTypeClasses #-}
@@ -1218,7 +1219,11 @@ withSingleContext ActionContext {..} ee@
                             let macroDeps = mapMaybe snd matchedDeps
                                 cppMacrosFile = setupDir </> relFileSetupMacrosH
                                 cppArgs = ["-optP-include", "-optP" ++ toFilePath cppMacrosFile]
+#if MIN_VERSION_Cabal(3,4,0)
+                            writeBinaryFileAtomic cppMacrosFile (encodeUtf8Builder (T.pack (C.generatePackageVersionMacros (packageVersion package) macroDeps)))
+#else
                             writeBinaryFileAtomic cppMacrosFile (encodeUtf8Builder (T.pack (C.generatePackageVersionMacros macroDeps)))
+#endif
                             return (packageDBArgs ++ depsArgs ++ cppArgs)
 
                         -- This branch is usually taken for builds, and
Index: b/src/Stack/BuildPlan.hs
===================================================================
--- a/src/Stack/BuildPlan.hs
+++ b/src/Stack/BuildPlan.hs
@@ -1,5 +1,6 @@
 {-# LANGUAGE NoImplicitPrelude #-}
 {-# LANGUAGE ConstraintKinds    #-}
+{-# LANGUAGE CPP                #-}
 {-# LANGUAGE DataKinds          #-}
 {-# LANGUAGE DeriveDataTypeable #-}
 {-# LANGUAGE FlexibleContexts   #-}
@@ -224,7 +225,11 @@ selectPackageBuildPlan platform compiler
     flagCombinations :: NonEmpty [(FlagName, Bool)]
     flagCombinations = mapM getOptions (genPackageFlags gpd)
       where
+#if MIN_VERSION_Cabal(3,4,0)
+        getOptions :: C.PackageFlag -> NonEmpty (FlagName, Bool)
+#else
         getOptions :: C.Flag -> NonEmpty (FlagName, Bool)
+#endif
         getOptions f
             | flagManual f = (fname, flagDefault f) :| []
             | flagDefault f = (fname, True) :| [(fname, False)]
Index: b/src/Stack/ConfigCmd.hs
===================================================================
--- a/src/Stack/ConfigCmd.hs
+++ b/src/Stack/ConfigCmd.hs
@@ -1,5 +1,6 @@
 {-# LANGUAGE NoImplicitPrelude #-}
 {-# LANGUAGE ConstraintKinds #-}
+{-# LANGUAGE CPP #-}
 {-# LANGUAGE FlexibleContexts #-}
 {-# LANGUAGE OverloadedStrings #-}
 {-# LANGUAGE ScopedTypeVariables #-}
@@ -17,9 +18,15 @@ module Stack.ConfigCmd
        ,cfgCmdName) where
 
 import           Stack.Prelude
+#if MIN_VERSION_aeson(2,0,0)
+import qualified Data.Aeson.Key as Key
+import qualified Data.Aeson.KeyMap as KeyMap
+#endif
 import           Data.ByteString.Builder (byteString)
 import qualified Data.Map.Merge.Strict as Map
+#if !MIN_VERSION_aeson(2,0,0)
 import qualified Data.HashMap.Strict as HMap
+#endif
 import qualified Data.Text as T
 import qualified Data.Yaml as Yaml
 import qualified Options.Applicative as OA
@@ -74,7 +81,11 @@ cfgCmdSet cmd = do
         liftIO (Yaml.decodeFileEither (toFilePath configFilePath)) >>= either throwM return
     newValue <- cfgCmdSetValue (parent configFilePath) cmd
     let cmdKey = cfgCmdSetOptionName cmd
+#if MIN_VERSION_aeson(2,0,0)
+        config' = KeyMap.insert (Key.fromText cmdKey) newValue config
+#else
         config' = HMap.insert cmdKey newValue config
+#endif
     if config' == config
         then logInfo
                  (fromString (toFilePath configFilePath) <>
Index: b/src/Stack/Init.hs
===================================================================
--- a/src/Stack/Init.hs
+++ b/src/Stack/Init.hs
@@ -1,5 +1,6 @@
 {-# LANGUAGE NoImplicitPrelude #-}
 {-# LANGUAGE ConstraintKinds       #-}
+{-# LANGUAGE CPP                   #-}
 {-# LANGUAGE FlexibleContexts      #-}
 {-# LANGUAGE MultiParamTypeClasses #-}
 {-# LANGUAGE OverloadedStrings     #-}
@@ -11,10 +12,15 @@ module Stack.Init
     ) where
 
 import           Stack.Prelude
+#if MIN_VERSION_aeson(2,0,0)
+import qualified Data.Aeson.KeyMap               as KeyMap
+#endif
 import qualified Data.ByteString.Builder         as B
 import qualified Data.ByteString.Char8           as BC
 import qualified Data.Foldable                   as F
+#if !MIN_VERSION_aeson(2,0,0)
 import qualified Data.HashMap.Strict             as HM
+#endif
 import qualified Data.IntMap                     as IntMap
 import           Data.List.Extra                 (groupSortOn)
 import qualified Data.List.NonEmpty              as NonEmpty
@@ -83,29 +89,29 @@ initProject currDir initOpts mresolver =
     let ignored = Map.difference bundle rbundle
         dupPkgMsg
             | dupPkgs /= [] =
-                "Warning (added by new or init): Some packages were found to \
-                \have names conflicting with others and have been commented \
-                \out in the packages section.\n"
+                "Warning (added by new or init): Some packages were found to " <>
+                "have names conflicting with others and have been commented " <>
+                "out in the packages section.\n"
             | otherwise = ""
 
         missingPkgMsg
             | Map.size ignored > 0 =
-                "Warning (added by new or init): Some packages were found to \
-                \be incompatible with the resolver and have been left commented \
-                \out in the packages section.\n"
+                "Warning (added by new or init): Some packages were found to " <>
+                "be incompatible with the resolver and have been left commented " <>
+                "out in the packages section.\n"
             | otherwise = ""
 
         extraDepMsg
             | Map.size extraDeps > 0 =
-                "Warning (added by new or init): Specified resolver could not \
-                \satisfy all dependencies. Some external packages have been \
-                \added as dependencies.\n"
+                "Warning (added by new or init): Specified resolver could not " <>
+                "satisfy all dependencies. Some external packages have been " <>
+                "added as dependencies.\n"
             | otherwise = ""
         makeUserMsg msgs =
             let msg = concat msgs
             in if msg /= "" then
-                  msg <> "You can omit this message by removing it from \
-                         \stack.yaml\n"
+                  msg <> "You can omit this message by removing it from " <>
+                         "stack.yaml\n"
                  else ""
 
         userMsg = makeUserMsg [dupPkgMsg, missingPkgMsg, extraDepMsg]
@@ -177,12 +183,20 @@ renderStackYaml p ignoredPackages dupPac
            B.byteString headerHelp
         <> B.byteString "\n\n"
         <> F.foldMap (goComment o) comments
+#if MIN_VERSION_aeson(2,0,0)
+        <> goOthers (o `KeyMap.difference` KeyMap.fromList comments)
+#else
         <> goOthers (o `HM.difference` HM.fromList comments)
+#endif
         <> B.byteString footerHelp
         <> "\n"
 
     goComment o (name, comment) =
+#if MIN_VERSION_aeson(2,0,0)
+        case (convert <$> KeyMap.lookup name o) <|> nonPresentValue name of
+#else
         case (convert <$> HM.lookup name o) <|> nonPresentValue name of
+#endif
             Nothing -> assert (name == "user-message") mempty
             Just v ->
                 B.byteString comment <>
@@ -226,7 +240,11 @@ renderStackYaml p ignoredPackages dupPac
         | otherwise = ""
 
     goOthers o
+#if MIN_VERSION_aeson(2,0,0)
+        | KeyMap.null o = mempty
+#else
         | HM.null o = mempty
+#endif
         | otherwise = assert False $ B.byteString $ Yaml.encode o
 
     -- Per Section Help
@@ -394,9 +412,9 @@ getWorkingResolverPlan initOpts pkgDirs0
                 Right (f, edeps)-> return (snapLoc, f, edeps, pkgDirs)
                 Left ignored
                     | Map.null available -> do
-                        logWarn "*** Could not find a working plan for any of \
-                                 \the user packages.\nProceeding to create a \
-                                 \config anyway."
+                        logWarn $ "*** Could not find a working plan for any of " <>
+                                "the user packages.\nProceeding to create a " <>
+                                "config anyway."
                         return (snapLoc, Map.empty, Map.empty, Map.empty)
                     | otherwise -> do
                         when (Map.size available == Map.size pkgDirs) $
@@ -537,9 +555,9 @@ cabalPackagesCheck cabaldirs dupErrMsg =
 
     when (nameMismatchPkgs /= []) $ do
         rels <- mapM prettyPath nameMismatchPkgs
-        error $ "Package name as defined in the .cabal file must match the \
-                \.cabal file name.\n\
-                \Please fix the following packages and try again:\n"
+        error $ "Package name as defined in the .cabal file must match the " <>
+                ".cabal file name.\n" <>
+                "Please fix the following packages and try again:\n"
                 <> T.unpack (utf8BuilderToText (formatGroup rels))
 
     let dupGroups = filter ((> 1) . length)
Index: b/src/Stack/New.hs
===================================================================
--- a/src/Stack/New.hs
+++ b/src/Stack/New.hs
@@ -1,5 +1,6 @@
 {-# LANGUAGE NoImplicitPrelude #-}
 {-# LANGUAGE ConstraintKinds #-}
+{-# LANGUAGE CPP #-}
 {-# LANGUAGE ScopedTypeVariables #-}
 {-# LANGUAGE DeriveDataTypeable #-}
 {-# LANGUAGE FlexibleContexts #-}
@@ -18,6 +19,9 @@ module Stack.New
 import           Stack.Prelude
 import           Control.Monad.Trans.Writer.Strict
 import           Data.Aeson as A
+#if MIN_VERSION_aeson(2,0,0)
+import qualified Data.Aeson.KeyMap as KeyMap
+#endif
 import qualified Data.ByteString.Base64 as B64
 import           Data.ByteString.Builder (lazyByteString)
 import qualified Data.ByteString.Lazy as LB
@@ -40,7 +44,9 @@ import           Stack.Constants
 import           Stack.Constants.Config
 import           Stack.Types.Config
 import           Stack.Types.TemplateName
+#if !MIN_VERSION_aeson(2,0,0)
 import qualified RIO.HashMap as HM
+#endif
 import           RIO.Process
 import qualified Text.Mustache as Mustache
 import qualified Text.Mustache.Render as Mustache
@@ -139,7 +145,7 @@ loadTemplate name logIt = do
         RepoPath rtp -> do
             let settings = settingsFromRepoTemplatePath rtp
             downloadFromUrl settings templateDir
-                            
+
   where
     loadLocalFile :: Path b File -> (ByteString -> Either String Text) -> RIO env Text
     loadLocalFile path extract = do
@@ -209,7 +215,11 @@ settingsFromRepoTemplatePath (RepoTempla
     , tplExtract = \bs -> do
         decodedJson <- eitherDecode (LB.fromStrict bs)
         case decodedJson of
+#if MIN_VERSION_aeson(2,0,0)
+          Object o | Just (String content) <- KeyMap.lookup "content" o -> do
+#else
           Object o | Just (String content) <- HM.lookup "content" o -> do
+#endif
                        let noNewlines = T.filter (/= '\n')
                        bsContent <- B64.decode $ T.encodeUtf8 (noNewlines content)
                        mapLeft show $ decodeUtf8' bsContent
@@ -258,8 +268,8 @@ applyTemplate project template noncePara
 
     let isPkgSpec f = ".cabal" `isSuffixOf` f || f == "package.yaml"
     unless (any isPkgSpec . M.keys $ files) $
-         throwM (InvalidTemplate template "Template does not contain a .cabal \
-                                          \or package.yaml file")
+         throwM (InvalidTemplate template
+           "Template does not contain a .cabal or package.yaml file")
 
     -- Apply Mustache templating to a single file within the project
     -- template.
Index: b/src/Stack/Package.hs
===================================================================
--- a/src/Stack/Package.hs
+++ b/src/Stack/Package.hs
@@ -32,6 +32,9 @@ import           Data.List (find, isPref
 import qualified Data.Map.Strict as M
 import qualified Data.Set as S
 import qualified Data.Text as T
+#if MIN_VERSION_Cabal(3,4,0)
+import           Distribution.CabalSpecVersion
+#endif
 import           Distribution.Compiler
 import           Distribution.ModuleName (ModuleName)
 import qualified Distribution.ModuleName as Cabal
@@ -128,7 +131,11 @@ resolvePackage packageConfig gpkg =
         (resolvePackageDescription packageConfig gpkg)
 
 packageFromPackageDescription :: PackageConfig
+#if MIN_VERSION_Cabal(3,4,0)
+                              -> [PackageFlag]
+#else
                               -> [D.Flag]
+#endif
                               -> PackageDescriptionPair
                               -> Package
 packageFromPackageDescription packageConfig pkgFlags (PackageDescriptionPair pkgNoMod pkg) =
@@ -190,7 +197,11 @@ packageFromPackageDescription packageCon
           (library pkg)
     , packageBuildType = buildType pkg
     , packageSetupDeps = msetupDeps
+#if MIN_VERSION_Cabal(3,4,0)
+    , packageCabalSpec = specVersion pkg
+#else
     , packageCabalSpec = either orLaterVersion id $ specVersionRaw pkg
+#endif
     }
   where
     extraLibNames = S.union subLibNames foreignLibNames
@@ -696,7 +707,11 @@ packageDescModulesAndFiles pkg = do
 
 -- | Resolve globbing of files (e.g. data files) to absolute paths.
 resolveGlobFiles
+#if MIN_VERSION_Cabal(3,4,0)
+  :: CabalSpecVersion -- ^ cabal file version
+#else
   :: Version -- ^ cabal file version
+#endif
   -> [String]
   -> RIO Ctx (Set (Path Abs File))
 resolveGlobFiles cabalFileVersion =
@@ -862,7 +877,11 @@ data PackageDescriptionPair = PackageDes
 resolvePackageDescription :: PackageConfig
                           -> GenericPackageDescription
                           -> PackageDescriptionPair
+#if MIN_VERSION_Cabal(3,4,0)
+resolvePackageDescription packageConfig (GenericPackageDescription desc _ defaultFlags mlib subLibs foreignLibs' exes tests benches) =
+#else
 resolvePackageDescription packageConfig (GenericPackageDescription desc defaultFlags mlib subLibs foreignLibs' exes tests benches) =
+#endif
     PackageDescriptionPair
       { pdpOrigBuildable = go False
       , pdpModifiedBuildable = go True
@@ -935,9 +954,17 @@ resolvePackageDescription packageConfig
 -- | Make a map from a list of flag specifications.
 --
 -- What is @flagManual@ for?
+#if MIN_VERSION_Cabal(3,4,0)
+flagMap :: [PackageFlag] -> Map FlagName Bool
+#else
 flagMap :: [Flag] -> Map FlagName Bool
+#endif
 flagMap = M.fromList . map pair
+#if MIN_VERSION_Cabal(3,4,0)
+  where pair :: PackageFlag -> (FlagName, Bool)
+#else
   where pair :: Flag -> (FlagName, Bool)
+#endif
         pair = flagName &&& flagDefault
 
 data ResolveConditions = ResolveConditions
@@ -986,7 +1013,11 @@ resolveConditions rc addDeps (CondNode l
                   case v of
                     OS os -> os == rcOS rc
                     Arch arch -> arch == rcArch rc
+#if MIN_VERSION_Cabal(3,4,0)
+                    PackageFlag flag ->
+#else
                     Flag flag ->
+#endif
                       fromMaybe False $ M.lookup flag (rcFlags rc)
                       -- NOTE:  ^^^^^ This should never happen, as all flags
                       -- which are used must be declared. Defaulting to
@@ -1394,7 +1425,13 @@ applyForceCustomBuild cabalVersion packa
           }
     | otherwise = package
   where
+#if MIN_VERSION_Cabal(3,4,0)
+    cabalVersionRange =
+      orLaterVersion $ mkVersion $ cabalSpecToVersionDigits $
+        packageCabalSpec package
+#else
     cabalVersionRange = packageCabalSpec package
+#endif
     forceCustomBuild =
       packageBuildType package == Simple &&
       not (cabalVersion `withinRange` cabalVersionRange)
Index: b/src/Stack/Script.hs
===================================================================
--- a/src/Stack/Script.hs
+++ b/src/Stack/Script.hs
@@ -18,6 +18,9 @@ import           Distribution.Compiler
 import           Distribution.ModuleName    (ModuleName)
 import qualified Distribution.PackageDescription as PD
 import qualified Distribution.Types.CondTree as C
+#if MIN_VERSION_Cabal(3,4,0)
+import           Distribution.Types.ModuleReexport
+#endif
 import           Distribution.Types.PackageName (mkPackageName)
 import           Distribution.Types.VersionRange (withinRange)
 import           Distribution.System        (Platform (..))
@@ -280,7 +283,11 @@ allExposedModules gpd = do
       mlibrary = snd . C.simplifyCondTree checkCond <$> PD.condLibrary gpd
   pure $ case mlibrary  of
     Just lib -> PD.exposedModules lib ++
+#if MIN_VERSION_Cabal(3,4,0)
+                map moduleReexportName (PD.reexportedModules lib)
+#else
                 map PD.moduleReexportName (PD.reexportedModules lib)
+#endif
     Nothing  -> mempty
 
 -- | The Stackage project introduced the concept of hidden packages,
Index: b/src/Stack/Setup.hs
===================================================================
--- a/src/Stack/Setup.hs
+++ b/src/Stack/Setup.hs
@@ -1,5 +1,6 @@
 {-# LANGUAGE NoImplicitPrelude #-}
 {-# LANGUAGE ConstraintKinds #-}
+{-# LANGUAGE CPP #-}
 {-# LANGUAGE DataKinds #-}
 {-# LANGUAGE DeriveFunctor #-}
 {-# LANGUAGE FlexibleContexts #-}
@@ -33,6 +34,9 @@ import              Conduit
 import              Control.Applicative (empty)
 import "cryptonite" Crypto.Hash (SHA1(..), SHA256(..))
 import              Pantry.Internal.AesonExtended
+#if MIN_VERSION_aeson(2,0,0)
+import qualified    Data.Aeson.KeyMap as KeyMap
+#endif
 import qualified    Data.ByteString as S
 import qualified    Data.ByteString.Lazy as LBS
 import qualified    Data.Conduit.Binary as CB
@@ -41,7 +45,9 @@ import qualified    Data.Conduit.List as
 import              Data.Conduit.Process.Typed (createSource)
 import              Data.Conduit.Zlib          (ungzip)
 import              Data.Foldable (maximumBy)
+#if !MIN_VERSION_aeson(2,0,0)
 import qualified    Data.HashMap.Strict as HashMap
+#endif
 import              Data.List hiding (concat, elem, maximumBy, any)
 import qualified    Data.Map as Map
 import qualified    Data.Set as Set
@@ -1988,16 +1994,28 @@ downloadStackExe platforms0 archiveInfo
 
     findArchive (SRIGithub val) pattern = do
         Object top <- return val
+#if MIN_VERSION_aeson(2,0,0)
+        Array assets <- KeyMap.lookup "assets" top
+#else
         Array assets <- HashMap.lookup "assets" top
+#endif
         getFirst $ fold $ fmap (First . findMatch pattern') assets
       where
         pattern' = mconcat ["-", pattern, "."]
 
         findMatch pattern'' (Object o) = do
+#if MIN_VERSION_aeson(2,0,0)
+            String name <- KeyMap.lookup "name" o
+#else
             String name <- HashMap.lookup "name" o
+#endif
             guard $ not $ ".asc" `T.isSuffixOf` name
             guard $ pattern'' `T.isInfixOf` name
+#if MIN_VERSION_aeson(2,0,0)
+            String url <- KeyMap.lookup "browser_download_url" o
+#else
             String url <- HashMap.lookup "browser_download_url" o
+#endif
             Just url
         findMatch _ _ = Nothing
     findArchive (SRIHaskellStackOrg hso) _ = pure $ hsoUrl hso
@@ -2095,7 +2113,11 @@ performPathChecking newFile executablePa
 getDownloadVersion :: StackReleaseInfo -> Maybe Version
 getDownloadVersion (SRIGithub val) = do
     Object o <- Just val
+#if MIN_VERSION_aeson(2,0,0)
+    String rawName <- KeyMap.lookup "name" o
+#else
     String rawName <- HashMap.lookup "name" o
+#endif
     -- drop the "v" at the beginning of the name
     parseVersion $ T.unpack (T.drop 1 rawName)
 getDownloadVersion (SRIHaskellStackOrg hso) = Just $ hsoVersion hso
Index: b/src/Stack/Types/Package.hs
===================================================================
--- a/src/Stack/Types/Package.hs
+++ b/src/Stack/Types/Package.hs
@@ -1,4 +1,5 @@
 {-# LANGUAGE NoImplicitPrelude #-}
+{-# LANGUAGE CPP #-}
 {-# LANGUAGE DeriveFunctor #-}
 {-# LANGUAGE DeriveGeneric #-}
 {-# LANGUAGE DeriveDataTypeable #-}
@@ -15,6 +16,9 @@ import qualified RIO.Text as T
 import           Data.Aeson (ToJSON (..), FromJSON (..), (.=), (.:), object, withObject)
 import qualified Data.Map as M
 import qualified Data.Set as Set
+#if MIN_VERSION_Cabal(3,4,0)
+import           Distribution.CabalSpecVersion
+#endif
 import           Distribution.Parsec (PError (..), PWarning (..), showPos)
 import qualified Distribution.SPDX.License as SPDX
 import           Distribution.License (License)
@@ -114,7 +118,11 @@ data Package =
           ,packageBuildType :: !BuildType                 -- ^ Package build-type.
           ,packageSetupDeps :: !(Maybe (Map PackageName VersionRange))
                                                           -- ^ If present: custom-setup dependencies
+#if MIN_VERSION_Cabal(3,4,0)
+          ,packageCabalSpec :: !CabalSpecVersion          -- ^ Cabal spec range
+#else
           ,packageCabalSpec :: !VersionRange              -- ^ Cabal spec range
+#endif
           }
  deriving (Show,Typeable)
 
Index: b/src/Stack/Types/Resolver.hs
===================================================================
--- a/src/Stack/Types/Resolver.hs
+++ b/src/Stack/Types/Resolver.hs
@@ -1,5 +1,6 @@
 {-# LANGUAGE NoImplicitPrelude #-}
 {-# LANGUAGE ConstraintKinds #-}
+{-# LANGUAGE CPP #-}
 {-# LANGUAGE DeriveDataTypeable #-}
 {-# LANGUAGE FlexibleContexts #-}
 {-# LANGUAGE FlexibleInstances #-}
@@ -19,7 +20,12 @@ module Stack.Types.Resolver
 import           Pantry.Internal.AesonExtended
                  (FromJSON, parseJSON,
                   withObject, (.:), withText)
+#if MIN_VERSION_aeson(2,0,0)
+import qualified Data.Aeson.Key as Key
+import qualified Data.Aeson.KeyMap as KeyMap
+#else
 import qualified Data.HashMap.Strict as HashMap
+#endif
 import qualified Data.IntMap.Strict as IntMap
 import qualified Data.Text as T
 import           Data.Text.Read (decimal)
@@ -86,8 +92,13 @@ instance FromJSON Snapshots where
     parseJSON = withObject "Snapshots" $ \o -> Snapshots
         <$> (o .: "nightly" >>= parseNightly)
         <*> fmap IntMap.unions (mapM (parseLTS . snd)
+#if MIN_VERSION_aeson(2,0,0)
+                $ filter (isLTS . Key.toText . fst)
+                $ KeyMap.toList o)
+#else
                 $ filter (isLTS . fst)
                 $ HashMap.toList o)
+#endif
       where
         parseNightly t =
             case parseSnapName t of
Index: b/stack-ghc-902.yaml
===================================================================
--- /dev/null
+++ b/stack-ghc-902.yaml
@@ -0,0 +1,27 @@
+resolver: lts-19.1
+
+packages:
+- .
+
+docker:
+  enable: false
+  repo: fpco/alpine-haskell-stack:8.10.4
+
+nix:
+  # --nix on the command-line to enable.
+  packages:
+    - zlib
+    - unzip
+flags:
+  stack:
+    developer-mode: true
+
+ghc-options:
+   "$locals": -fhide-source-paths
+
+extra-deps:
+- mustache-2.4.0@sha256:09a2eac7b8d093231cd8c5355dc87d7f882be77aebf88de18c4d9e612beca453,3345
+- unordered-containers-0.2.16.0@sha256:859ec9a017e51194755cb8a445b767afc5ce0ac991cd50b0f96abd31b3687aab,5217
+drop-packages:
+# See https://github.com/commercialhaskell/stack/pull/4712
+- cabal-install
Index: b/stack.cabal
===================================================================
--- a/stack.cabal
+++ b/stack.cabal
@@ -474,6 +474,8 @@ executable stack-integration-test
     other-modules:
         StackTest
         Paths_stack
+    autogen-modules:
+        Paths_stack
 
     default-language: Haskell2010
     ghc-options:
@@ -608,6 +610,8 @@ test-suite stack-test
         Stack.Types.TemplateNameSpec
         Stack.UploadSpec
         Paths_stack
+    autogen-modules:
+        Paths_stack
 
     default-language:   Haskell2010
     ghc-options: