Add a criterion benchmark

bench/Bench.hs

@@ -0,0 +1,29 @@
+import Criterion.Main
+import Language.Haskell.GhcMod.Target
+import TestUtils
+import Dir
+import System.IO.Temp
+import System.Process hiding (env)
+import Control.Monad
+
+main = defaultMain [
+    env setup $ \dir -> bgroup "simple-cabal" [
+        bench "nop" $ whnfIO (simpleCabalNop dir 1)
+      , bench "nop10" $ whnfIO (simpleCabalNop dir 10)
+      ]
+  ]
+
+setup = do
+  tdir <- createTempDirectory "/tmp" "ghc-mod-bench"
+  system $ "cp -rv \"bench/data/simple-cabal/\" \""++ tdir ++"\""
+
+  simpleCabalNop tdir 1 -- warmup dist/
+
+  return tdir
+
+simpleCabalNop :: FilePath -> Int -> IO ()
+simpleCabalNop dir n = withDirectory_ (dir </> "simple-cabal") $ do
+  _ <- runGhcModT defaultOptions $
+       forM_ [1..n] $ \_ -> do
+           runGmlT [Left "Main.hs"] (return ())
+  return ()

bench/data/simple-cabal/Main.hs

@@ -0,0 +1,4 @@
+module Main where
+
+main :: IO ()
+main = putStrLn "Hello, Haskell!"

bench/data/simple-cabal/Setup.hs

@@ -0,0 +1,2 @@
+import Distribution.Simple
+main = defaultMain

bench/data/simple-cabal/simple-cabal.cabal

@@ -0,0 +1,13 @@
+name:                simple-cabal
+version:             0.1.0.0
+license:             BSD3
+license-file:        LICENSE
+author:              Daniel Gröber
+maintainer:          dxld@darkboxed.org
+build-type:          Simple
+cabal-version:       >=1.10
+
+executable simple-cabal
+  main-is:             Main.hs
+  build-depends:       base
+  default-language:    Haskell2010

ghc-mod.cabal

@@ -94,6 +94,8 @@ Extra-Source-Files:     ChangeLog
                         test/data/stack-project/app/*.hs
                         test/data/stack-project/src/*.hs
                         test/data/stack-project/test/*.hs
+                        bench/data/simple-cabal/simple-cabal.cabal
+                        bench/data/simple-cabal/*.hs
 
 Custom-Setup
   Setup-Depends:         base
@@ -294,6 +296,33 @@ Test-Suite spec
   Build-Depends:        hspec >= 2.0.0
   X-Build-Depends-Like: CLibName
 
+Benchmark criterion
+  Type:                 exitcode-stdio-1.0
+  Default-Language:     Haskell2010
+  Default-Extensions:   ScopedTypeVariables, RecordWildCards, NamedFieldPuns,
+                        ConstraintKinds, FlexibleContexts,
+                        DataKinds, KindSignatures, TypeOperators, ViewPatterns
+  HS-Source-Dirs:       bench, test
+  Main-Is:              Bench.hs
+  Build-Depends:        base
+                      , directory < 1.3
+                      , filepath  < 1.5
+                      , pretty    < 1.2
+                      , process   < 1.5
+                      , split     < 0.3
+                      , mtl       < 2.3 && >= 2.0
+                      , ghc       < 8.1
+
+                      , monad-journal     < 0.8 && >= 0.4
+                      , fclabels          == 2.0.*
+                      , temporary         < 1.3
+
+                      , hspec >= 2.0.0
+
+                      , criterion
+
+                      , ghc-mod
+
 Source-Repository head
   Type:                 git
   Location:             https://github.com/DanielG/ghc-mod.git