Add regression test for #11411

Author: sheaf

cabal-testsuite/PackageTests/Regression/T11411/T11411.cabal

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+cabal-version: 3.0
+name:          T11411
+version:       0.1.0.0
+build-type:    Simple
+
+library
+  hs-source-dirs:
+    src
+  exposed-modules:
+    Hello
+  build-depends:
+    base
+  build-tool-depends:
+    alex:alex
+  default-language:
+    Haskell2010

cabal-testsuite/PackageTests/Regression/T11411/cabal.project

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+packages: .

cabal-testsuite/PackageTests/Regression/T11411/cabal.test.hs

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+import Test.Cabal.Prelude
+
+-- Test for #11411: cabal should re-invoke build tools (in this case, alex)
+-- whose version changes in between builds.
+main :: IO ()
+main = cabalTest $ withRepo "repo" $ do
+  -- Expect failure on first build: alex 3.4 outputs invalid Haskell.
+  fails $ cabal "v2-build" ["all", "-c", "any.alex==3.4.*"]
+  -- Second build should succeed: switching to alex 3.5 should cause cabal
+  -- to re-invoke alex, which will output valid Haskell this time around.
+  -- If this fails, it's because cabal didn't re-run the preprocessing step.
+  cabal "v2-build" ["all", "-c", "any.alex==3.5.*"]

cabal-testsuite/PackageTests/Regression/T11411/repo/alex-3.4.0.0/alex.cabal

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+cabal-version: 3.0
+name:          alex
+version:       3.4.0.0
+build-type:    Simple
+
+executable alex
+  main-is:          Main.hs
+  hs-source-dirs:   app
+  build-depends:    base
+  default-language: Haskell2010

cabal-testsuite/PackageTests/Regression/T11411/repo/alex-3.4.0.0/app/Main.hs

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+module Main where
+
+import System.Environment (getArgs)
+
+-- Fake alex 3.4: writes invalid Haskell so that GHC rejects the output.
+main :: IO ()
+main = do
+  args <- getArgs
+  case args of
+    "--version" : _ ->
+      putStrLn "Alex version 3.4.0, (c) 2003 Chris Dornan and Simon Marlow"
+    _ ->
+      writeFile (outputFile args) "THIS IS NOT VALID HASKELL\n"
+
+outputFile :: [String] -> FilePath
+outputFile ("-o" : f : _) = f
+outputFile (_ : rest)     = outputFile rest
+outputFile []             = error "alex: no -o flag"

cabal-testsuite/PackageTests/Regression/T11411/repo/alex-3.5.0.0/alex.cabal

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+cabal-version: 3.0
+name:          alex
+version:       3.5.0.0
+build-type:    Simple
+
+executable alex
+  main-is:          Main.hs
+  hs-source-dirs:   app
+  build-depends:    base
+  default-language: Haskell2010

cabal-testsuite/PackageTests/Regression/T11411/repo/alex-3.5.0.0/app/Main.hs

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+module Main where
+
+import System.Environment (getArgs)
+
+-- Fake alex 3.5: writes valid Haskell so that GHC accepts the output.
+main :: IO ()
+main = do
+  args <- getArgs
+  case args of
+    "--version" : _ ->
+      putStrLn "Alex version 3.5.0, (c) 2003 Chris Dornan and Simon Marlow"
+    _ ->
+      writeFile (outputFile args) "module Hello where\nhello :: String\nhello = \"hello from alex 3.5\"\n"
+
+outputFile :: [String] -> FilePath
+outputFile ("-o" : f : _) = f
+outputFile (_ : rest)     = outputFile rest
+outputFile []             = error "alex: no -o flag"

cabal-testsuite/PackageTests/Regression/T11411/src/Hello.x

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+(contents irrelevant)