Add tests Paths_ autogen module + default.extensions

Fixes haskell#5086

The haskell#5054 links to
commercialhaskell/stack#3789 which says

- `Ensure you have OverloadedStrings and RebindableSyntax extensions
  enabled.`

So we warn only in that case. Only `OverloadeStrings` (or
`OverloadedLists`) or `RebindableSyntax` seems to be ok.

Author: phadej

Cabal/Cabal.cabal

@@ -82,6 +82,8 @@ extra-source-files:
   tests/ParserTests/regressions/encoding-0.8.cabal
   tests/ParserTests/regressions/encoding-0.8.expr
   tests/ParserTests/regressions/encoding-0.8.format
+  tests/ParserTests/regressions/extensions-paths-5054.cabal
+  tests/ParserTests/regressions/extensions-paths-5054.check
   tests/ParserTests/regressions/generics-sop.cabal
   tests/ParserTests/regressions/generics-sop.expr
   tests/ParserTests/regressions/generics-sop.format

Cabal/Distribution/PackageDescription/Check.hs

@@ -151,6 +151,7 @@ checkPackage gpkg mpkg =
   ++ checkFlagNames gpkg
   ++ checkUnusedFlags gpkg
   ++ checkUnicodeXFields gpkg
+  ++ checkPathsModuleExtensions pkg
   where
     pkg = fromMaybe (flattenPackageDescription gpkg) mpkg
 
@@ -1664,6 +1665,34 @@ checkUnicodeXFields gpd
         , toDListOf (L.buildInfos         . L.customFieldsBI . traverse) gpd
         ]
 
+-- | cabal-version <2.2 + Paths_module + default-extensions: doesn't build.
+checkPathsModuleExtensions :: PackageDescription -> [PackageCheck]
+checkPathsModuleExtensions pd
+    | specVersion pd >= mkVersion [2,2] = []
+    | any checkBI (allBuildInfo pd) || any checkLib (allLibraries pd)
+        = return $ PackageBuildImpossible $ unwords
+            [ "The package uses RebindableSyntax with OverloadedStrings or OverloadedLists"
+            , "in default-extensions, and also Paths_ autogen module."
+            , "That configuration is known to cause compile failures with Cabal < 2.2."
+            , "To use these default-extensions with Paths_ autogen module"
+            , "specify at least 'cabal-version: 2.2'."
+            ]
+    | otherwise = []
+  where
+    mn = autogenPathsModuleName pd
+
+    checkLib :: Library -> Bool
+    checkLib l = mn `elem` exposedModules l && checkExts (l ^. L.defaultExtensions)
+
+    checkBI :: BuildInfo -> Bool
+    checkBI bi = mn `elem` otherModules bi && checkExts (bi ^. L.defaultExtensions)
+
+    checkExts exts = rebind `elem` exts && (strings `elem` exts || lists `elem` exts)
+      where
+        rebind  = EnableExtension RebindableSyntax
+        strings = EnableExtension OverloadedStrings
+        lists   = EnableExtension OverloadedLists
+
 checkDevelopmentOnlyFlagsBuildInfo :: BuildInfo -> [PackageCheck]
 checkDevelopmentOnlyFlagsBuildInfo bi =
   catMaybes [

Cabal/Distribution/Types/PackageDescription.hs

@@ -369,22 +369,15 @@ withForeignLib pkg_descr f =
 -- dependencies.
 allBuildInfo :: PackageDescription -> [BuildInfo]
 allBuildInfo pkg_descr = [ bi | lib <- allLibraries pkg_descr
-                              , let bi = libBuildInfo lib
-                              , buildable bi ]
-                      ++ [ bi | flib <- foreignLibs pkg_descr
-                              , let bi = foreignLibBuildInfo flib
-                              , buildable bi ]
-                      ++ [ bi | exe <- executables pkg_descr
-                              , let bi = buildInfo exe
-                              , buildable bi ]
-                      ++ [ bi | tst <- testSuites pkg_descr
-                              , let bi = testBuildInfo tst
-                              , buildable bi ]
-                      ++ [ bi | tst <- benchmarks pkg_descr
-                              , let bi = benchmarkBuildInfo tst
-                              , buildable bi ]
-  --FIXME: many of the places where this is used, we actually want to look at
-  --       unbuildable bits too, probably need separate functions
+                               , let bi = libBuildInfo lib ]
+                       ++ [ bi | flib <- foreignLibs pkg_descr
+                               , let bi = foreignLibBuildInfo flib ]
+                       ++ [ bi | exe <- executables pkg_descr
+                               , let bi = buildInfo exe ]
+                       ++ [ bi | tst <- testSuites pkg_descr
+                               , let bi = testBuildInfo tst ]
+                       ++ [ bi | tst <- benchmarks pkg_descr
+                               , let bi = benchmarkBuildInfo tst ]
 
 -- | Return all of the 'BuildInfo's of enabled components, i.e., all of
 -- the ones that would be built if you run @./Setup build@.

Cabal/tests/CheckTests.hs

@@ -27,6 +27,7 @@ checkTests = testGroup "regressions"
     [ checkTest "nothing-unicode.cabal"
     , checkTest "haddock-api-2.18.1-check.cabal"
     , checkTest "issue-774.cabal"
+    , checkTest "extensions-paths-5054.cabal"
     ]
 
 checkTest :: FilePath -> TestTree

Cabal/tests/ParserTests/regressions/extensions-paths-5054.cabal

@@ -0,0 +1,39 @@
+name:         extensions-paths
+version:      5054
+category:     Test
+maintainer:   Oleg Grenrus
+license:      BSD3
+license-file: LICENSe
+synopsis:     Paths_pkg module + "bad" extensions + old cabal
+description:
+  Only cabal-version: 2.2 or later will build Paths_pkg ok with
+
+  * RebindableSyntax and
+
+  * OverloadedLists or OverloadedStrings
+
+  `fromList` or `fromString` will be out-of-scope when compiling Paths_ module.
+
+  Other extensions (like NoImplicitPrelude) were handled before
+build-type:    Simple
+cabal-version: 1.12
+
+library
+  default-language: Haskell2010
+  exposed-modules:  Issue Paths_extensions_paths
+  default-extensions:
+    RebindableSyntax
+    OverloadedStrings
+
+test-suite tests
+  default-language: Haskell2010
+  main-is: Test.hs
+  type: exitcode-stdio-1.0
+  if os(linux)
+    other-modules: Paths_extensions_paths
+  else:
+    buildable: False
+
+  default-extensions:
+    OverloadedLists
+    RebindableSyntax

Cabal/tests/ParserTests/regressions/extensions-paths-5054.check

@@ -0,0 +1 @@
+The package uses RebindableSyntax with OverloadedStrings or OverloadedLists in default-extensions, and also Paths_ autogen module. That configuration is known to cause compile failures with Cabal < 2.2. To use these default-extensions with Paths_ autogen module specify at least 'cabal-version: 2.2'.