Merge tag 'v0.9.4.3'

v0.9.4.3

16 files changed, 488 insertions, 48 deletions

diff --git a/.circleci/config.yml b/.circleci/config.yml
index e6a538c..e1e9020 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -12,17 +12,17 @@ workflows:
 jobs:
   build:
     docker:
-      - image: 'fpco/stack-build:latest'
+      - image: 'haskell:8.6'
 
     steps:
       - checkout
       - restore_cache:
-          key: 'v2-stylish-haskell-{{ arch }}-{{ .Branch }}'
+          key: 'v3-stylish-haskell-{{ arch }}-{{ .Branch }}'
       - run:
           name: 'Build, install and test'
           command: 'stack build --test --copy-bins --jobs=1'
       - save_cache:
-          key: 'v2-stylish-haskell-{{ arch }}-{{ .Branch }}-{{ .Revision }}'
+          key: 'v3-stylish-haskell-{{ arch }}-{{ .Branch }}-{{ .Revision }}'
           paths:
             - '~/.stack-work'
             - '~/.stack'
diff --git a/.circleci/release.sh b/.circleci/release.sh
index 5586d24..a55247f 100755
--- a/.circleci/release.sh
+++ b/.circleci/release.sh
@@ -19,14 +19,15 @@ if [[ -z "$TAG" ]]; then
 fi
 
 # Install ghr
-GHR_VERSION="v0.5.4"
-wget --quiet \
-    "https://github.com/tcnksm/ghr/releases/download/${GHR_VERSION}/ghr_${GHR_VERSION}_linux_386.zip"
-unzip ghr_${GHR_VERSION}_linux_386.zip
+GHR_VERSION="v0.13.0"
+curl --silent -L -O \
+    "https://github.com/tcnksm/ghr/releases/download/${GHR_VERSION}/ghr_${GHR_VERSION}_linux_386.tar.gz"
+tar xf ghr_${GHR_VERSION}_linux_386.tar.gz
+mv ghr_${GHR_VERSION}_linux_386/ghr .
 
 # Install upx
 UPX_VERSION="3.94"
-wget --quiet \
+curl --silent -L -O \
     "https://github.com/upx/upx/releases/download/v${UPX_VERSION}/upx-${UPX_VERSION}-amd64_linux.tar.xz"
 tar xf upx-${UPX_VERSION}-amd64_linux.tar.xz
 mv upx-${UPX_VERSION}-amd64_linux/upx .
diff --git a/CHANGELOG b/CHANGELOG
index 0bf78c4..6eca483 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,5 +1,28 @@
 # CHANGELOG
 
+- 0.9.4.3 (2019-10-29)
+    * Bump release script
+    * Bump `Cabal` to 3.0
+
+- 0.9.4.2 (2019-10-29)
+    * Bump release script
+
+- 0.9.4.1 (2019-10-29)
+    * Bump release script
+
+- 0.9.4.0 (2019-10-29)
+    * Read language extensions from `.cabal` file (by Georgy Lukyanov)
+
+- 0.9.3.1 (2019-10-08)
+    * Fix CircleCI configuration
+
+- 0.9.3.0 (2019-10-08)
+    * Bump `optparse-applicative` to 0.15
+    * Don't remove page breaks in the trailing whitespace step (by Chris
+      Perivolaropoulos)
+    * Add `with_module_name` option to `list_align` for import styling (by
+      Rupert Horlick)
+
 - 0.9.2.2 (2019-06-12)
     * Bump `semigroups` to 0.19
     * Bump `haskell-src-exts` to 1.21
diff --git a/README.markdown b/README.markdown
index a3406c6..8f56ea6 100644
--- a/README.markdown
+++ b/README.markdown
@@ -112,7 +112,8 @@ Or you can define `formatprg`
 
 and then use `gq`.
 
-Alternatively, [vim-autoformat] supports stylish-haskell. To have it automatically reformat the files on save, add to your vimrc:
+Alternatively, [vim-autoformat] supports stylish-haskell. To have it
+automatically reformat the files on save, add to your vimrc:
 
 ```vim
 autocmd BufWrite *.hs :Autoformat
@@ -120,12 +121,14 @@ autocmd BufWrite *.hs :Autoformat
 autocmd FileType haskell let b:autoformat_autoindent=0
 ```
 
-[vim-autoformat]: https://github.com/Chiel92/vim-autoformat
+There are also plugins that run stylish-haskell automatically when you save a
+Haskell file:
 
-There is also the [vim-stylish-haskell] plugin, which runs stylish-haskell
-automatically when you save a Haskell file.
+* [vim-stylish-haskell]
+* [vim-stylishask]
 
 [vim-stylish-haskell]: https://github.com/nbouscal/vim-stylish-haskell
+[vim-stylishask]: https://github.com/alx741/vim-stylishask
 
 Emacs integration
 -----------------
diff --git a/data/stylish-haskell.yaml b/data/stylish-haskell.yaml
index 6d43499..401d384 100644
--- a/data/stylish-haskell.yaml
+++ b/data/stylish-haskell.yaml
@@ -56,6 +56,18 @@ steps:
       #   > import qualified Data.List      as List (concat, foldl, foldr, head,
       #   >                                 init, last, length)
       #
+      # - with_module_name: Import list is aligned `list_padding` spaces after
+      #   the module name.
+      #
+      #   > import qualified Data.List      as List (concat, foldl, foldr, head,
+      #                          init, last, length)
+      #
+      #   This is mainly intended for use with `pad_module_names: false`.
+      #
+      #   > import qualified Data.List as List (concat, foldl, foldr, head,
+      #                          init, last, length, scanl, scanr, take, drop,
+      #                          sort, nub)
+      #
       # - new_line: Import list starts always on new line.
       #
       #   > import qualified Data.List      as List
@@ -229,3 +241,9 @@ newline: native
 # language_extensions:
   # - TemplateHaskell
   # - QuasiQuotes
+
+# Attempt to find the cabal file in ancestors of the current directory, and
+# parse options (currently only language extensions) from that.
+#
+# Default: true
+cabal: true
diff --git a/lib/Language/Haskell/Stylish/Config.hs b/lib/Language/Haskell/Stylish/Config.hs
index ad30498..8f43131 100644
--- a/lib/Language/Haskell/Stylish/Config.hs
+++ b/lib/Language/Haskell/Stylish/Config.hs
@@ -17,22 +17,22 @@ import qualified Data.Aeson                                       as A
 import qualified Data.Aeson.Types                                 as A
 import qualified Data.ByteString                                  as B
 import qualified Data.FileEmbed                                   as FileEmbed
-import           Data.List                                        (inits,
-                                                                   intercalate)
+import           Data.List                                        (intercalate,
+                                                                   nub)
 import           Data.Map                                         (Map)
 import qualified Data.Map                                         as M
 import           Data.Maybe                                       (fromMaybe)
 import           Data.Yaml                                        (decodeEither',
                                                                    prettyPrintParseException)
 import           System.Directory
-import           System.FilePath                                  (joinPath,
-                                                                   splitPath,
-                                                                   (</>))
+import           System.FilePath                                  ((</>))
 import qualified System.IO                                        as IO (Newline (..),
                                                                          nativeNewline)
 
 
 --------------------------------------------------------------------------------
+import qualified Language.Haskell.Stylish.Config.Cabal            as Cabal
+import           Language.Haskell.Stylish.Config.Internal
 import           Language.Haskell.Stylish.Step
 import qualified Language.Haskell.Stylish.Step.Imports            as Imports
 import qualified Language.Haskell.Stylish.Step.LanguagePragmas    as LanguagePragmas
@@ -54,6 +54,7 @@ data Config = Config
     , configColumns            :: Int
     , configLanguageExtensions :: [String]
     , configNewline            :: IO.Newline
+    , configCabal              :: Bool
     }
 
 
@@ -79,24 +80,19 @@ configFilePath verbose Nothing              = do
     current    <- getCurrentDirectory
     configPath <- getXdgDirectory XdgConfig "stylish-haskell"
     home       <- getHomeDirectory
-    mbConfig   <- search $
+    mbConfig   <- search verbose $
         [d </> configFileName | d <- ancestors current] ++
         [configPath </> "config.yaml", home </> configFileName]
 
     return mbConfig
-  where
-    -- All ancestors of a dir (including that dir)
-    ancestors :: FilePath -> [FilePath]
-    ancestors = init . map joinPath . reverse . inits . splitPath
-
-    search :: [FilePath] -> IO (Maybe FilePath)
-    search []       = return Nothing
-    search (f : fs) = do
-        -- TODO Maybe catch an error here, dir might be unreadable
-        exists <- doesFileExist f
-        verbose $ f ++ if exists then " exists" else " does not exist"
-        if exists then return (Just f) else search fs
 
+search :: Verbose -> [FilePath] -> IO (Maybe FilePath)
+search _ []             = return Nothing
+search verbose (f : fs) = do
+    -- TODO Maybe catch an error here, dir might be unreadable
+    exists <- doesFileExist f
+    verbose $ f ++ if exists then " exists" else " does not exist"
+    if exists then return (Just f) else search verbose fs
 
 --------------------------------------------------------------------------------
 loadConfig :: Verbose -> Maybe FilePath -> IO Config
@@ -107,7 +103,15 @@ loadConfig verbose userSpecified = do
     case decodeEither' bytes of
         Left err     -> error $
             "Language.Haskell.Stylish.Config.loadConfig: " ++ prettyPrintParseException err
-        Right config -> return config
+        Right config -> do
+          cabalLanguageExtensions <- if configCabal config
+            then map show <$> Cabal.findLanguageExtensions verbose
+            else pure []
+
+          return $ config
+            { configLanguageExtensions = nub $
+                configLanguageExtensions config ++ cabalLanguageExtensions
+            }
 
 
 --------------------------------------------------------------------------------
@@ -119,6 +123,7 @@ parseConfig (A.Object o) = do
         <*> (o A..:? "columns"             A..!= 80)
         <*> (o A..:? "language_extensions" A..!= [])
         <*> (o A..:? "newline"             >>= parseEnum newlines IO.nativeNewline)
+        <*> (o A..:? "cabal"               A..!= True)
 
     -- Then fill in the steps based on the partial config we already have
     stepValues <- o A..: "steps" :: A.Parser [A.Value]
@@ -209,9 +214,10 @@ parseImports config o = Imports.step
         ]
 
     listAligns =
-        [ ("new_line",    Imports.NewLine)
-        , ("with_alias",  Imports.WithAlias)
-        , ("after_alias", Imports.AfterAlias)
+        [ ("new_line",          Imports.NewLine)
+        , ("with_module_name",  Imports.WithModuleName)
+        , ("with_alias",        Imports.WithAlias)
+        , ("after_alias",       Imports.AfterAlias)
         ]
 
     longListAligns =
diff --git a/lib/Language/Haskell/Stylish/Config/Cabal.hs b/lib/Language/Haskell/Stylish/Config/Cabal.hs
new file mode 100644
index 0000000..0160af4
--- /dev/null
+++ b/lib/Language/Haskell/Stylish/Config/Cabal.hs
@@ -0,0 +1,92 @@
+--------------------------------------------------------------------------------
+module Language.Haskell.Stylish.Config.Cabal
+    ( findLanguageExtensions
+    ) where
+
+
+--------------------------------------------------------------------------------
+import           Data.Either                              (isRight)
+import           Data.List                                (nub)
+import           Data.Maybe                               (maybeToList)
+import qualified Distribution.PackageDescription          as Cabal
+import qualified Distribution.PackageDescription.Parsec   as Cabal
+import qualified Distribution.Simple.Utils                as Cabal
+import qualified Distribution.Types.CondTree              as Cabal
+import qualified Distribution.Verbosity                   as Cabal
+import qualified Language.Haskell.Extension               as Language
+import           Language.Haskell.Stylish.Verbose
+import           System.Directory                         (getCurrentDirectory)
+
+
+--------------------------------------------------------------------------------
+import           Language.Haskell.Stylish.Config.Internal
+
+
+--------------------------------------------------------------------------------
+findLanguageExtensions :: Verbose -> IO [Language.KnownExtension]
+findLanguageExtensions verbose =
+    findCabalFile verbose >>=
+    maybe (pure []) (readDefaultLanguageExtensions verbose)
+
+
+--------------------------------------------------------------------------------
+-- | Find the closest .cabal file, possibly going up the directory structure.
+findCabalFile :: Verbose -> IO (Maybe FilePath)
+findCabalFile verbose = do
+  potentialProjectRoots <- ancestors <$> getCurrentDirectory
+  potentialCabalFile <- filter isRight <$>
+    traverse Cabal.findPackageDesc potentialProjectRoots
+  case potentialCabalFile of
+    [Right cabalFile] -> return (Just cabalFile)
+    _ -> do
+      verbose $ ".cabal file not found, directories searched: " <>
+        show potentialProjectRoots
+      verbose $ "Stylish Haskell will work basing on LANGUAGE pragmas in source files."
+      return Nothing
+
+
+--------------------------------------------------------------------------------
+-- | Extract @default-extensions@ fields from a @.cabal@ file
+readDefaultLanguageExtensions :: Verbose -> FilePath -> IO [Language.KnownExtension]
+readDefaultLanguageExtensions verbose cabalFile = do
+  verbose $ "Parsing " <> cabalFile <> "..."
+  packageDescription <- Cabal.readGenericPackageDescription Cabal.silent cabalFile
+  let library :: [Cabal.Library]
+      library = maybeToList $ fst . Cabal.ignoreConditions <$>
+        Cabal.condLibrary packageDescription
+
+      subLibraries :: [Cabal.Library]
+      subLibraries = fst . Cabal.ignoreConditions . snd <$>
+        Cabal.condSubLibraries packageDescription
+
+      executables :: [Cabal.Executable]
+      executables = fst . Cabal.ignoreConditions . snd <$>
+        Cabal.condExecutables packageDescription
+
+      testSuites :: [Cabal.TestSuite]
+      testSuites = fst . Cabal.ignoreConditions . snd <$>
+        Cabal.condTestSuites packageDescription
+
+      benchmarks :: [Cabal.Benchmark]
+      benchmarks = fst . Cabal.ignoreConditions . snd <$>
+        Cabal.condBenchmarks packageDescription
+
+      gatherBuildInfos :: [Cabal.BuildInfo]
+      gatherBuildInfos = map Cabal.libBuildInfo library <>
+                         map Cabal.libBuildInfo subLibraries <>
+                         map Cabal.buildInfo executables <>
+                         map Cabal.testBuildInfo testSuites <>
+                         map Cabal.benchmarkBuildInfo benchmarks
+
+      defaultExtensions :: [Language.KnownExtension]
+      defaultExtensions = map fromEnabled . filter isEnabled $
+        concatMap Cabal.defaultExtensions gatherBuildInfos
+        where isEnabled (Language.EnableExtension _) = True
+              isEnabled _                            = False
+
+              fromEnabled (Language.EnableExtension x) = x
+              fromEnabled x                             =
+                error $ "Language.Haskell.Stylish.Config.readLanguageExtensions: " <>
+                        "invalid LANGUAGE pragma:  " <> show x
+  verbose $ "Gathered default-extensions: " <> show defaultExtensions
+  pure $ nub defaultExtensions
diff --git a/lib/Language/Haskell/Stylish/Config/Internal.hs b/lib/Language/Haskell/Stylish/Config/Internal.hs
new file mode 100644
index 0000000..b6160f9
--- /dev/null
+++ b/lib/Language/Haskell/Stylish/Config/Internal.hs
@@ -0,0 +1,15 @@
+--------------------------------------------------------------------------------
+module Language.Haskell.Stylish.Config.Internal
+    ( ancestors
+    ) where
+
+
+--------------------------------------------------------------------------------
+import           Data.List       (inits)
+import           System.FilePath (joinPath, splitPath)
+
+
+--------------------------------------------------------------------------------
+-- All ancestors of a dir (including that dir)
+ancestors :: FilePath -> [FilePath]
+ancestors = map joinPath . reverse . dropWhile null . inits . splitPath
diff --git a/lib/Language/Haskell/Stylish/Step/Imports.hs b/lib/Language/Haskell/Stylish/Step/Imports.hs
index fc035a2..4ceb802 100644
--- a/lib/Language/Haskell/Stylish/Step/Imports.hs
+++ b/lib/Language/Haskell/Stylish/Step/Imports.hs
@@ -72,6 +72,7 @@ data ImportAlign
 
 data ListAlign
     = NewLine
+    | WithModuleName
     | WithAlias
     | AfterAlias
     deriving (Eq, Show)
@@ -291,10 +292,11 @@ prettyImport columns Options{..} padQualified padName longest imp
         . withLast (++ (maybeSpace ++ ")"))
 
     inlineWrapper = case listAlign of
-        NewLine    -> (paddedNoSpecBase :) . wrapRest columns listPadding'
-        WithAlias  -> wrap columns paddedBase (inlineBaseLength + 1)
+        NewLine        -> (paddedNoSpecBase :) . wrapRest columns listPadding'
+        WithModuleName -> wrap columns paddedBase (withModuleNameBaseLength + 4)
+        WithAlias      -> wrap columns paddedBase (inlineBaseLength + 1)
         -- Add 1 extra space to ensure same padding as in original code.
-        AfterAlias -> withTail ((' ' : maybeSpace) ++)
+        AfterAlias     -> withTail ((' ' : maybeSpace) ++)
             . wrap columns paddedBase (afterAliasBaseLength + 1)
 
     inlineWithBreakWrap = paddedNoSpecBase : wrapRest columns listPadding'
@@ -349,6 +351,8 @@ prettyImport columns Options{..} padQualified padName longest imp
     inlineBaseLength = length $
                        base' (padImport $ compoundImportName imp) [] []
 
+    withModuleNameBaseLength = length $ base' "" [] []
+
     afterAliasBaseLength = length $ base' (padImport $ compoundImportName imp)
         ["as " ++ as | H.ModuleName _ as <- maybeToList $ H.importAs imp] []
 
diff --git a/lib/Language/Haskell/Stylish/Step/TrailingWhitespace.hs b/lib/Language/Haskell/Stylish/Step/TrailingWhitespace.hs
index dbc594c..e41bace 100644
--- a/lib/Language/Haskell/Stylish/Step/TrailingWhitespace.hs
+++ b/lib/Language/Haskell/Stylish/Step/TrailingWhitespace.hs
@@ -19,4 +19,9 @@ dropTrailingWhitespace = reverse . dropWhile isSpace . reverse
 
 --------------------------------------------------------------------------------
 step :: Step
-step = makeStep "TrailingWhitespace" $ \ls _ -> map dropTrailingWhitespace ls
+step = makeStep "TrailingWhitespace" $ \ls _ -> map dropTrailingWhitespace' ls
+  where
+    dropTrailingWhitespace' l = case l of
+      -- Preserve page breaks
+      "\12" -> l
+      _     -> dropTrailingWhitespace l
diff --git a/stack.yaml b/stack.yaml
index 7a5f68c..2d7969b 100644
--- a/stack.yaml
+++ b/stack.yaml
@@ -1,4 +1,6 @@
-resolver: lts-13.19
-
+resolver: lts-14.6
 packages:
-  - '.'
+- '.'
+
+extra-deps:
+- 'Cabal-3.0.0.0'
diff --git a/stylish-haskell.cabal b/stylish-haskell.cabal
index 1890a4b..52da455 100644
--- a/stylish-haskell.cabal
+++ b/stylish-haskell.cabal
@@ -1,5 +1,5 @@
 Name:          stylish-haskell
-Version:       0.9.2.2
+Version:       0.9.4.3
 Synopsis:      Haskell code prettifier
 Homepage:      https://github.com/jaspervdj/stylish-haskell
 License:       BSD3
@@ -41,6 +41,8 @@ Library
     Language.Haskell.Stylish.Align
     Language.Haskell.Stylish.Block
     Language.Haskell.Stylish.Config
+    Language.Haskell.Stylish.Config.Cabal
+    Language.Haskell.Stylish.Config.Internal
     Language.Haskell.Stylish.Editor
     Language.Haskell.Stylish.Parse
     Language.Haskell.Stylish.Step
@@ -52,6 +54,7 @@ Library
     aeson            >= 0.6    && < 1.5,
     base             >= 4.8    && < 5,
     bytestring       >= 0.9    && < 0.11,
+    Cabal            >= 2.4    && < 3.1,
     containers       >= 0.3    && < 0.7,
     directory        >= 1.2.3  && < 1.4,
     filepath         >= 1.1    && < 1.5,
@@ -70,11 +73,12 @@ Executable stylish-haskell
   Build-depends:
     stylish-haskell,
     strict               >= 0.3  && < 0.4,
-    optparse-applicative >= 0.12 && < 0.15,
+    optparse-applicative >= 0.12 && < 0.16,
     -- Copied from regular dependencies...
     aeson            >= 0.6    && < 1.5,
     base             >= 4.8    && < 5,
     bytestring       >= 0.9    && < 0.11,
+    Cabal            >= 2.4    && < 3.1,
     containers       >= 0.3    && < 0.7,
     directory        >= 1.2.3  && < 1.4,
     filepath         >= 1.1    && < 1.5,
@@ -94,18 +98,21 @@ Test-suite stylish-haskell-tests
     Language.Haskell.Stylish.Align
     Language.Haskell.Stylish.Block
     Language.Haskell.Stylish.Config
+    Language.Haskell.Stylish.Config.Cabal
+    Language.Haskell.Stylish.Config.Internal
+    Language.Haskell.Stylish.Config.Tests
     Language.Haskell.Stylish.Editor
     Language.Haskell.Stylish.Parse
     Language.Haskell.Stylish.Parse.Tests
     Language.Haskell.Stylish.Step
-    Language.Haskell.Stylish.Step.SimpleAlign
-    Language.Haskell.Stylish.Step.SimpleAlign.Tests
-    Language.Haskell.Stylish.Step.Squash
-    Language.Haskell.Stylish.Step.Squash.Tests
     Language.Haskell.Stylish.Step.Imports
     Language.Haskell.Stylish.Step.Imports.Tests
     Language.Haskell.Stylish.Step.LanguagePragmas
     Language.Haskell.Stylish.Step.LanguagePragmas.Tests
+    Language.Haskell.Stylish.Step.SimpleAlign
+    Language.Haskell.Stylish.Step.SimpleAlign.Tests
+    Language.Haskell.Stylish.Step.Squash
+    Language.Haskell.Stylish.Step.Squash.Tests
     Language.Haskell.Stylish.Step.Tabs
     Language.Haskell.Stylish.Step.Tabs.Tests
     Language.Haskell.Stylish.Step.TrailingWhitespace
@@ -120,10 +127,12 @@ Test-suite stylish-haskell-tests
     HUnit                >= 1.2 && < 1.7,
     test-framework       >= 0.4 && < 0.9,
     test-framework-hunit >= 0.2 && < 0.4,
+    random               >= 1.1,
     -- Copied from regular dependencies...
     aeson            >= 0.6    && < 1.5,
     base             >= 4.8    && < 5,
     bytestring       >= 0.9    && < 0.11,
+    Cabal            >= 2.4    && < 3.1,
     containers       >= 0.3    && < 0.7,
     directory        >= 1.2.3  && < 1.4,
     filepath         >= 1.1    && < 1.5,
diff --git a/tests/Language/Haskell/Stylish/Config/Tests.hs b/tests/Language/Haskell/Stylish/Config/Tests.hs
new file mode 100644
index 0000000..f62b571
--- /dev/null
+++ b/tests/Language/Haskell/Stylish/Config/Tests.hs
@@ -0,0 +1,142 @@
+module Language.Haskell.Stylish.Config.Tests
+    ( tests
+    ) where
+
+
+--------------------------------------------------------------------------------
+import           Control.Exception               hiding (assert)
+import qualified Data.Set                        as Set
+import           System.Directory
+import           System.FilePath                 ((</>))
+import           System.IO.Error
+import           System.Random
+import           Test.Framework                  (Test, testGroup)
+import           Test.Framework.Providers.HUnit  (testCase)
+import           Test.HUnit                      (Assertion, assert)
+--------------------------------------------------------------------------------
+import           Language.Haskell.Stylish.Config
+
+--------------------------------------------------------------------------------
+tests :: Test
+tests = testGroup "Language.Haskell.Stylish.Config"
+    [ testCase "Extensions extracted correctly from .cabal file"
+               testExtensionsFromDotCabal
+    , testCase "Extensions extracted correctly from .stylish-haskell.yaml file"
+               testExtensionsFromDotStylish
+    , testCase "Extensions extracted correctly from .stylish-haskell.yaml and .cabal files"
+               testExtensionsFromBoth
+    ]
+--------------------------------------------------------------------------------
+
+-- | Create a temporary directory with a randomised name built from the template provided
+createTempDirectory :: String -> IO FilePath
+createTempDirectory template  = do
+  tmpRootDir <- getTemporaryDirectory
+  dirId <- randomIO :: IO Word
+  findTempName tmpRootDir dirId
+  where
+    findTempName :: FilePath -> Word -> IO FilePath
+    findTempName tmpRootDir x = do
+      let dirpath = tmpRootDir </> template ++ show x
+      r <- try $ createDirectory dirpath
+      case r of
+        Right _ -> return dirpath
+        Left  e | isAlreadyExistsError e -> findTempName tmpRootDir (x+1)
+                | otherwise              -> ioError e
+
+-- | Perform an action inside a temporary directory tree and purge the tree afterwords
+withTestDirTree :: IO a -> IO a
+withTestDirTree action = bracket
+    ((,) <$> getCurrentDirectory <*> createTempDirectory "stylish_haskell")
+    (\(current, temp) ->
+        setCurrentDirectory current *>
+        removeDirectoryRecursive temp)
+    (\(_, temp) -> setCurrentDirectory temp *> action)
+
+-- | Put an example config files (.cabal/.stylish-haskell.yaml/both)
+-- into the current directory and extract extensions from it.
+createFilesAndGetExtensions :: [(FilePath, String)] -> IO Extensions
+createFilesAndGetExtensions files = withTestDirTree $ do
+  mapM_ (\(k, v) -> writeFile k v) files
+  -- create an empty directory and change into it
+  createDirectory "src"
+  setCurrentDirectory "src"
+  -- from that directory read the config file and extract extensions
+  -- to make sure the search for .cabal file works
+  config <- loadConfig (const (pure ())) Nothing
+  pure $ configLanguageExtensions config
+
+--------------------------------------------------------------------------------
+testExtensionsFromDotCabal :: Assertion
+testExtensionsFromDotCabal =
+  assert $ (expected ==) . Set.fromList <$>
+    createFilesAndGetExtensions [("test.cabal", dotCabal True)]
+    where
+      expected = Set.fromList ["ScopedTypeVariables", "DataKinds"]
+
+--------------------------------------------------------------------------------
+testExtensionsFromDotStylish :: Assertion
+testExtensionsFromDotStylish =
+  assert $ (expected ==) . Set.fromList <$>
+    createFilesAndGetExtensions [(".stylish-haskell.yaml", dotStylish)]
+    where
+      expected = Set.fromList ["TemplateHaskell", "QuasiQuotes"]
+
+--------------------------------------------------------------------------------
+testExtensionsFromBoth :: Assertion
+testExtensionsFromBoth =
+  assert $ (expected ==) . Set.fromList <$>
+    createFilesAndGetExtensions [ ("test.cabal", dotCabal True)
+                                , (".stylish-haskell.yaml", dotStylish)]
+    where
+      expected = Set.fromList
+        ["ScopedTypeVariables", "DataKinds", "TemplateHaskell", "QuasiQuotes"]
+
+-- | Example cabal file borrowed from
+--   https://www.haskell.org/cabal/users-guide/developing-packages.html
+--   with some default-extensions added
+dotCabal :: Bool -> String
+dotCabal includeExtensions = unlines $
+  [ "name:            TestPackage"
+  , "version:         0.0"
+  , "synopsis:        Package with library and two programs"
+  , "license:         BSD3"
+  , "author:          Angela Author"
+  , "build-type:      Simple"
+  , "cabal-version:   >= 1.2"
+  , ""
+  , "library"
+  , "   build-depends:   HUnit"
+  , "   exposed-modules: A, B, C"
+  ] ++
+  [if includeExtensions then "   default-extensions: ScopedTypeVariables"
+                        else ""]
+  ++
+  [ ""
+  , "executable program1"
+  , "   main-is:         Main.hs"
+  , "   hs-source-dirs:  prog1"
+  , "   other-modules:   A, B"
+  ] ++
+  [if includeExtensions then "   default-extensions: DataKinds"
+                        else ""]
+
+-- | Example .stylish-haskell.yaml
+dotStylish :: String
+dotStylish = unlines $
+  [ "steps:"
+  , "  - imports:"
+  , "      align: none"
+  , "      list_align: after_alias"
+  , "      long_list_align: inline"
+  , "      separate_lists: true"
+  , "  - language_pragmas:"
+  , "      style: vertical"
+  , "      align: false"
+  , "      remove_redundant: true"
+  , "  - trailing_whitespace: {}"
+  , "columns: 110"
+  , "language_extensions:"
+  , "  - TemplateHaskell"
+  , "  - QuasiQuotes"
+  ]
diff --git a/tests/Language/Haskell/Stylish/Step/Imports/Tests.hs b/tests/Language/Haskell/Stylish/Step/Imports/Tests.hs
index 67c7c5a..760018a 100644
--- a/tests/Language/Haskell/Stylish/Step/Imports/Tests.hs
+++ b/tests/Language/Haskell/Stylish/Step/Imports/Tests.hs
@@ -32,11 +32,15 @@ tests = testGroup "Language.Haskell.Stylish.Step.Imports.Tests"
     , testCase "case 06" case06
     , testCase "case 07" case07
     , testCase "case 08" case08
+    , testCase "case 08b" case08b
     , testCase "case 09" case09
     , testCase "case 10" case10
     , testCase "case 11" case11
+    , testCase "case 11b" case11b
     , testCase "case 12" case12
+    , testCase "case 12b" case12b
     , testCase "case 13" case13
+    , testCase "case 13b" case13b
     , testCase "case 14" case14
     , testCase "case 15" case15
     , testCase "case 16" case16
@@ -50,6 +54,7 @@ tests = testGroup "Language.Haskell.Stylish.Step.Imports.Tests"
     , testCase "case 21" case21
     , testCase "case 22" case22
     , testCase "case 23" case23
+    , testCase "case 23b" case23b
     , testCase "case 24" case24
     , testCase "case 25" case25
     , testCase "case 26 (issue 185)" case26
@@ -213,6 +218,28 @@ case08 = expected
 
 
 --------------------------------------------------------------------------------
+case08b :: Assertion
+case08b = expected
+    @=? testStep (step 80 $ Options Global WithModuleName True Inline Inherit (LPConstant 4) True False) input
+  where
+    expected = unlines
+        ["module Herp where"
+        , ""
+        , "import           Control.Monad"
+        , "import           Data.List           as List (concat, foldl, foldr, head, init,"
+        , "                     last, length, map, null, reverse, tail, (++))"
+        , "import           Data.Map            (Map, insert, lookup, (!))"
+        , "import qualified Data.Map            as M"
+        , "import           Only.Instances      ()"
+        , ""
+        , "import           Foo                 (Bar (..))"
+        , "import           Herp.Derp.Internals hiding (foo)"
+        , ""
+        , "herp = putStrLn \"import Hello world\""
+        ]
+
+
+--------------------------------------------------------------------------------
 case09 :: Assertion
 case09 = expected
     @=? testStep (step 80 $ Options Global WithAlias True Multiline Inherit (LPConstant 4) True False) input
@@ -313,6 +340,27 @@ case11 = expected
         ]
 
 
+case11b :: Assertion
+case11b = expected
+    @=? testStep (step 80 $ Options Group WithModuleName True Inline Inherit (LPConstant 4) True False) input
+  where
+    expected = unlines
+        [ "module Herp where"
+        , ""
+        , "import           Control.Monad"
+        , "import           Data.List      as List (concat, foldl, foldr, head, init, last,"
+        , "                     length, map, null, reverse, tail, (++))"
+        , "import           Data.Map       (Map, insert, lookup, (!))"
+        , "import qualified Data.Map       as M"
+        , "import           Only.Instances ()"
+        , ""
+        , "import Foo                 (Bar (..))"
+        , "import Herp.Derp.Internals hiding (foo)"
+        , ""
+        , "herp = putStrLn \"import Hello world\""
+        ]
+
+
 --------------------------------------------------------------------------------
 case12 :: Assertion
 case12 = expected
@@ -329,6 +377,18 @@ case12 = expected
 
 
 --------------------------------------------------------------------------------
+case12b :: Assertion
+case12b = expected
+    @=? testStep (step 80 $ Options Group WithModuleName True Inline Inherit (LPConstant 2) True False) input'
+  where
+    input' = unlines
+        [ "import Data.List (map)"
+        ]
+
+    expected = input'
+
+
+--------------------------------------------------------------------------------
 case13 :: Assertion
 case13 = expected
     @=? testStep (step 80 $ Options None WithAlias True InlineWithBreak Inherit (LPConstant 4) True False) input'
@@ -346,6 +406,23 @@ case13 = expected
 
 
 --------------------------------------------------------------------------------
+case13b :: Assertion
+case13b = expected
+    @=? testStep (step 80 $ Options None WithModuleName True InlineWithBreak Inherit (LPConstant 4) True False) input'
+  where
+    input' = unlines
+        [ "import qualified Data.List as List (concat, foldl, foldr, head, init,"
+        , "    last, length, map, null, reverse, tail, (++))"
+        ]
+
+    expected = unlines
+        [ "import qualified Data.List as List"
+        , "    (concat, foldl, foldr, head, init, last, length, map, null, reverse, tail,"
+        , "    (++))"
+        ]
+
+
+--------------------------------------------------------------------------------
 case14 :: Assertion
 case14 = expected
     @=? testStep
@@ -451,6 +528,7 @@ case18 = expected @=? testStep
         , "import Data.Acid as Acid (closeAcidState, createCheckpoint, openLocalStateFrom)"
         ]
 
+
 --------------------------------------------------------------------------------
 case19 :: Assertion
 case19 = expected @=? testStep
@@ -467,6 +545,7 @@ case19 = expected @=? testStep
         , "                 intersperse)"
         ]
 
+
 case19b :: Assertion
 case19b = expected @=? testStep
     (step 40 $ Options File NewLine True InlineWithBreak RightAfter (LPConstant 17) True False) case19input
@@ -482,6 +561,7 @@ case19b = expected @=? testStep
         , "                 intersperse)"
         ]
 
+
 case19c :: Assertion
 case19c = expected @=? testStep
     (step 40 $ Options File NewLine True InlineWithBreak RightAfter LPModuleName True False) case19input
@@ -497,6 +577,7 @@ case19c = expected @=? testStep
         , "       intersperse)"
         ]
 
+
 case19d :: Assertion
 case19d = expected @=? testStep
     (step 40 $ Options Global NewLine True InlineWithBreak RightAfter LPModuleName True False) case19input
@@ -512,6 +593,7 @@ case19d = expected @=? testStep
         , "                 intersperse)"
         ]
 
+
 case19input :: String
 case19input = unlines
         [ "import Prelude.Compat hiding (foldMap)"
@@ -520,6 +602,7 @@ case19input = unlines
         , "import Data.List (foldl', intercalate, intersperse)"
         ]
 
+
 --------------------------------------------------------------------------------
 case20 :: Assertion
 case20 = expected
@@ -538,6 +621,7 @@ case20 = expected
         , "import Data.Set (empty)"
         ]
 
+
 --------------------------------------------------------------------------------
 case21 :: Assertion
 case21 = expected
@@ -568,6 +652,7 @@ case21 = expected
         , "import X9 hiding (x, y, z, x)"
         ]
 
+
 --------------------------------------------------------------------------------
 case22 :: Assertion
 case22 = expected
@@ -594,6 +679,7 @@ case22 = expected
           "theLongestNameYet, shortName)"
         ]
 
+
 --------------------------------------------------------------------------------
 case23 :: Assertion
 case23 = expected
@@ -618,6 +704,33 @@ case23 = expected
         , "import Data.ALongName.Foo (Foo, Goo, Boo)"
         ]
 
+
+--------------------------------------------------------------------------------
+case23b :: Assertion
+case23b = expected
+    @=? testStep (step 40 $ Options None WithModuleName False Inline Inherit (LPConstant 4) True True) input'
+  where
+    expected = unlines
+        [ "import Data.Acid ( AcidState )"
+        , "import Data.Default.Class"
+        , "           ( Default (def) )"
+        , ""
+        , "import Data.Monoid ( (<>) )"
+        , ""
+        , "import Data.ALongName.Foo ( Boo, Foo,"
+        , "           Goo )"
+        ]
+
+    input' = unlines
+        [ "import Data.Acid (AcidState)"
+        , "import Data.Default.Class (Default(def))"
+        , ""
+        , "import Data.Monoid ((<>) )"
+        , ""
+        , "import Data.ALongName.Foo (Foo, Goo, Boo)"
+        ]
+
+
 --------------------------------------------------------------------------------
 case24 :: Assertion
 case24 = expected
@@ -641,6 +754,7 @@ case24 = expected
           "GooReallyLong, BooReallyLong)"
         ]
 
+
 --------------------------------------------------------------------------------
 case25 :: Assertion
 case25 = expected
diff --git a/tests/Language/Haskell/Stylish/Step/TrailingWhitespace/Tests.hs b/tests/Language/Haskell/Stylish/Step/TrailingWhitespace/Tests.hs
index 1394edb..0593c0a 100644
--- a/tests/Language/Haskell/Stylish/Step/TrailingWhitespace/Tests.hs
+++ b/tests/Language/Haskell/Stylish/Step/TrailingWhitespace/Tests.hs
@@ -28,12 +28,16 @@ case01 = expected @=? testStep step input
   where
     input = unlines
         [ "module Main where"
-        , " "
+        , " \t"
         , "data Foo = Bar | Qux\t "
+        , "\12"    -- page break
+        , "   \12" -- malformed page break
         ]
 
     expected = unlines
         [ "module Main where"
         , ""
         , "data Foo = Bar | Qux"
+        , "\12" -- page break
+        , ""
         ]
diff --git a/tests/TestSuite.hs b/tests/TestSuite.hs
index 27963a0..b5bec90 100644
--- a/tests/TestSuite.hs
+++ b/tests/TestSuite.hs
@@ -9,6 +9,7 @@ import           Test.Framework                                         (default
 
 
 --------------------------------------------------------------------------------
+import qualified Language.Haskell.Stylish.Config.Tests
 import qualified Language.Haskell.Stylish.Parse.Tests
 import qualified Language.Haskell.Stylish.Step.Imports.Tests
 import qualified Language.Haskell.Stylish.Step.LanguagePragmas.Tests
@@ -23,6 +24,7 @@ import qualified Language.Haskell.Stylish.Step.UnicodeSyntax.Tests
 main :: IO ()
 main = defaultMain
     [ Language.Haskell.Stylish.Parse.Tests.tests
+    , Language.Haskell.Stylish.Config.Tests.tests
     , Language.Haskell.Stylish.Step.Imports.Tests.tests
     , Language.Haskell.Stylish.Step.LanguagePragmas.Tests.tests
     , Language.Haskell.Stylish.Step.SimpleAlign.Tests.tests