Merge pull request #83/#124 from sniperrifle2004/import

brittany.cabal

@@ -67,6 +67,9 @@ library {
     Language.Haskell.Brittany.Internal.Layouters.Expr
     Language.Haskell.Brittany.Internal.Layouters.Stmt
     Language.Haskell.Brittany.Internal.Layouters.Pattern
+    Language.Haskell.Brittany.Internal.Layouters.IE
+    Language.Haskell.Brittany.Internal.Layouters.Import
+    Language.Haskell.Brittany.Internal.Layouters.Module
     Language.Haskell.Brittany.Internal.Transformations.Alt
     Language.Haskell.Brittany.Internal.Transformations.Floating
     Language.Haskell.Brittany.Internal.Transformations.Par

src-literatetests/10-tests.blt

@@ -565,3 +565,297 @@ func =
        ]
     ++ [ccccccccccccccccccccccccccccccccccccccccccccccccccccccccc]
 
+
+###############################################################################
+###############################################################################
+###############################################################################
+#group module
+###############################################################################
+###############################################################################
+###############################################################################
+
+#test simple
+module Main where
+
+#test no-exports
+module Main () where
+
+#test one-export
+module Main (main) where
+
+#test several-exports
+module Main (main, test1, test2) where
+
+#test many-exports
+module Main
+  ( main
+  , test1
+  , test2
+  , test3
+  , test4
+  , test5
+  , test6
+  , test7
+  , test8
+  , test9
+  )
+where
+
+#test exports-with-comments
+module Main
+  ( main
+  -- main
+  , test1
+  , test2
+  -- Test 3
+  , test3
+  , test4
+  -- Test 5
+  , test5
+  -- Test 6
+  )
+where
+
+#test simple-export-with-things
+module Main (Test(..)) where
+
+#test simple-export-with-module-contents
+module Main (module Main) where
+
+#test export-with-things
+module Main (Test(Test, a, b)) where
+
+#test export-with-things-comment
+-- comment1
+
+module Main
+  ( Test(Test, a, b)
+  , foo -- comment2
+  ) -- comment3
+where
+
+#test export-with-empty-thing
+module Main (Test()) where
+
+#test empty-with-comment
+-- Intentionally left empty
+
+###############################################################################
+###############################################################################
+###############################################################################
+#group module.import
+###############################################################################
+###############################################################################
+###############################################################################
+
+#test simple-import
+import           Data.List
+
+#test simple-import-alias
+import           Data.List                               as L
+
+#test simple-qualified-import
+import qualified Data.List
+
+#test simple-qualified-import-alias
+import qualified Data.List                               as L
+
+#test simple-safe
+import safe      Data.List                               as L
+
+#test simple-source
+import {-# SOURCE #-} Data.List                           ( )
+
+#test simple-safe-qualified
+import safe qualified Data.List
+
+#test simple-safe-qualified-source
+import {-# SOURCE #-} safe qualified Data.List
+
+#test simple-qualified-package
+import qualified "base" Data.List
+
+#test qualifier-effect
+import {-# SOURCE #-} safe qualified "base" Data.List    as L
+import {-# SOURCE #-} safe qualified "base" Data.List     ( )
+import {-# SOURCE #-} safe qualified Data.List     hiding ( )
+
+#test instances-only
+import qualified Data.List                                ( )
+
+#test one-element
+import           Data.List                                ( nub )
+
+#test several-elements
+import           Data.List                                ( nub
+                                                          , foldl'
+                                                          , indexElem
+                                                          )
+
+#test a-ridiculous-amount-of-elements
+import           Test                                     ( Long
+                                                          , list
+                                                          , with
+                                                          , items
+                                                          , that
+                                                          , will
+                                                          , not
+                                                          , quite
+                                                          , fit
+                                                          , onA
+                                                          , single
+                                                          , line
+                                                          , anymore
+                                                          )
+
+#test with-things
+import           Test                                     ( T
+                                                          , T2()
+                                                          , T3(..)
+                                                          , T4(T4)
+                                                          , T5(T5, t5)
+                                                          , T6((<|>))
+                                                          , (+)
+                                                          )
+
+#test hiding
+import           Test                              hiding ( )
+import           Test                                    as T
+                                                   hiding ( )
+
+#test long-module-name
+import           TestJustShortEnoughModuleNameLikeThisOne ( )
+import           TestJustAbitToLongModuleNameLikeThisOneIs
+                                                          ( )
+
+import           TestJustShortEnoughModuleNameLikeThisOn as T
+import           TestJustAbitToLongModuleNameLikeThisOneI
+                                                         as T
+
+import           TestJustShortEnoughModuleNameLike hiding ( )
+import           TestJustAbitToLongModuleNameLikeTh
+                                                   hiding ( )
+
+import           MoreThanSufficientlyLongModuleNameWithSome
+                                                          ( items
+                                                          , that
+                                                          , will
+                                                          , not
+                                                          , fit
+                                                          , inA
+                                                          , compact
+                                                          , layout
+                                                          )
+
+import {-# SOURCE #-} safe qualified "qualifiers" AlsoAff ( )
+import {-# SOURCE #-} safe qualified "qualifiers" AlsoAffe
+                                                          ( )
+
+import {-# SOURCE #-} safe qualified "qualifiers" AlsoAf as T
+import {-# SOURCE #-} safe qualified "qualifiers" AlsoAff
+                                                         as T
+import {-# SOURCE #-} safe qualified "qualifier" A hiding ( )
+import {-# SOURCE #-} safe qualified "qualifiers" A
+                                                   hiding ( )
+
+#test import-with-comments
+-- Test
+import           Data.List                                ( nub ) -- Test
+{- Test -}
+import qualified Data.List                               as L
+                                                          ( foldl' ) {- Test -}
+
+-- Test
+import           Test                                     ( test )
+
+#test import-with-comments-2
+
+import           Test                                     ( abc
+                                                          , def
+                                                          -- comment
+                                                          )
+
+#test import-with-comments-3
+
+import           Test                                     ( abc
+                                                          -- comment
+                                                          )
+
+#test import-with-comments-4
+import           Test                                     ( abc
+                                                          -- comment
+                                                          , def
+                                                          , ghi
+                                                          {- comment -}
+                                                          , jkl
+                                                          -- comment
+                                                          )
+
+#test import-with-comments-5
+import           Test                                     ( -- comment
+                                                          )
+
+#test long-bindings
+import           Test                                     ( longbindingNameThatoverflowsColum
+                                                          )
+import           Test                                     ( Long
+                                                            ( List
+                                                            , Of
+                                                            , Things
+                                                            )
+                                                          )
+
+#test things-with-with-comments
+import           Test                                     ( Thing
+                                                            ( -- Comments
+                                                            )
+                                                          )
+import           Test                                     ( Thing
+                                                            ( Item
+                                                            -- and Comment
+                                                            )
+                                                          )
+import           Test                                     ( Thing
+                                                            ( With
+                                                            -- Comments
+                                                            , and
+                                                            -- also
+                                                            , items
+                                                            -- !
+                                                            )
+                                                          )
+#test prefer-dense-empty-list
+import           VeryLongModuleNameThatCouldEvenCauseAnEmptyBindingListToExpandIntoMultipleLine
+                                                          ( )
+
+#test preamble full-preamble
+{-# LANGUAGE BangPatterns #-}
+
+{-
+ - Test module
+ -}
+module Test
+  ( test1
+  -- ^ test
+  , test2
+  -- | test
+  , test3
+  , test4
+  , test5
+  , test6
+  , test7
+  , test8
+  , test9
+  , test10
+  -- Test 10
+  )
+where
+
+-- Test
+import           Data.List                                ( nub ) -- Test
+{- Test -}
+import qualified Data.List                               as L
+                                                          ( foldl' ) {- Test -}
+
+-- Test
+import           Test                                     ( test )

src-literatetests/Main.hs

@@ -169,11 +169,14 @@ defaultTestConfig = Config
     , _lconfig_indentWhereSpecial        = coerce True
     , _lconfig_indentListSpecial         = coerce True
     , _lconfig_importColumn              = coerce (60 :: Int)
+    , _lconfig_importAsColumn            = coerce (60 :: Int)
     , _lconfig_altChooser                = coerce $ AltChooserBoundedSearch 3
     , _lconfig_columnAlignMode           = coerce (ColumnAlignModeMajority 0.7)
     , _lconfig_alignmentLimit            = coerce (30 :: Int)
     , _lconfig_alignmentBreakOnMultiline = coerce True
     , _lconfig_hangingTypeSignature      = coerce False
+    , _lconfig_reformatModulePreamble    = coerce True
+    , _lconfig_allowSingleLineExportList = coerce True
     }
   , _conf_errorHandling = (_conf_errorHandling staticDefaultConfig)
     { _econf_omit_output_valid_check = coerce True

src-literatetests/tests-context-free.blt

@@ -598,6 +598,259 @@ func =
       ]
     ++ [ccccccccccccccccccccccccccccccccccccccccccccccccccccccccc]
 
+###############################################################################
+###############################################################################
+###############################################################################
+#group module
+###############################################################################
+###############################################################################
+###############################################################################
+
+#test simple
+module Main where
+
+#test no-exports
+module Main () where
+
+#test one-export
+module Main (main) where
+
+#test several-exports
+module Main (main, test1, test2) where
+
+#test many-exports
+module Main
+  ( main
+  , test1
+  , test2
+  , test3
+  , test4
+  , test5
+  , test6
+  , test7
+  , test8
+  , test9
+  )
+where
+
+#test exports-with-comments
+module Main
+  ( main
+  -- main
+  , test1
+  , test2
+  -- Test 3
+  , test3
+  , test4
+  -- Test 5
+  , test5
+  -- Test 6
+  )
+where
+
+#test simple-export-with-things
+module Main (Test(..)) where
+
+#test simple-export-with-module-contents
+module Main (module Main) where
+
+#test export-with-things
+module Main (Test(Test, a, b)) where
+
+#test export-with-empty-thing
+module Main (Test()) where
+
+#test empty-with-comment
+-- Intentionally left empty
+
+###############################################################################
+###############################################################################
+###############################################################################
+#group import
+###############################################################################
+###############################################################################
+###############################################################################
+
+#test simple-import
+import Data.List
+
+#test simple-import-alias
+import Data.List as L
+
+#test simple-qualified-import
+import qualified Data.List
+
+#test simple-qualified-import-alias
+import qualified Data.List as L
+
+#test simple-safe
+import safe Data.List as L
+
+#test simple-source
+import {-# SOURCE #-} Data.List ()
+
+#test simple-safe-qualified
+import safe qualified Data.List hiding (nub)
+
+#test simple-safe-qualified-source
+import {-# SOURCE #-} safe qualified Data.List
+
+#test simple-qualified-package
+import qualified "base" Data.List
+
+#test qualifier-effect
+import {-# SOURCE #-} safe qualified "base" Data.List as L
+import {-# SOURCE #-} safe qualified "base" Data.List ()
+import {-# SOURCE #-} safe qualified Data.List hiding ()
+
+#test instances-only
+import qualified Data.List ()
+
+#test one-element
+import Data.List (nub)
+
+#test several-elements
+import Data.List (nub, foldl', indexElem)
+
+#test a-ridiculous-amount-of-elements
+import Test
+  ( Long
+  , list
+  , with
+  , items
+  , that
+  , will
+  , not
+  , quite
+  , fit
+  , onA
+  , single
+  , line
+  , anymore
+  )
+
+#test with-things
+import Test (T, T2(), T3(..), T4(T4), T5(T5, t5), T6((<|>)), (+))
+
+#test hiding
+import Test hiding ()
+import Test as T hiding ()
+
+#test long-module-name
+import TestJustShortEnoughModuleNameLikeThisOne ()
+import TestJustAbitToLongModuleNameLikeThisOneIs ()
+import TestJustShortEnoughModuleNameLikeThisOn as T
+import TestJustAbitToLongModuleNameLikeThisOneI as T
+import TestJustShortEnoughModuleNameLike hiding ()
+import TestJustAbitToLongModuleNameLikeTh hiding ()
+import MoreThanSufficientlyLongModuleNameWithSome
+  (items, that, will, not, fit, inA, compact, layout)
+
+#test import-with-comments
+-- Test
+import Data.List (nub) -- Test
+{- Test -}
+import qualified Data.List as L (foldl') {- Test -}
+
+#test import-with-comments-2
+
+import Test
+  ( abc
+  , def
+  -- comment
+  )
+
+#test import-with-comments-3
+
+import Test
+  ( abc
+  -- comment
+  )
+
+#test import-with-comments-4
+import Test
+  ( abc
+  -- comment
+  , def
+  , ghi
+  {- comment -}
+  , jkl
+  -- comment
+  )
+
+-- Test
+import Test (test)
+
+#test import-with-comments-5
+import Test
+  ( -- comment
+  )
+
+#test long-bindings
+import Test (longbindingNameThatoverflowsColum)
+import Test (Long(List, Of, Things))
+
+#test things-with-with-comments
+import Test
+  ( Thing
+    ( With
+    -- Comments
+    , and
+    -- also
+    , items
+    -- !
+    )
+  )
+import Test
+  ( Thing
+    ( Item
+    -- and Comment
+    )
+  )
+import Test
+  ( Thing
+    ( With
+    -- Comments
+    , and
+    -- also
+    , items
+    -- !
+    )
+  )
+
+#test prefer-dense-empty-list
+import VeryLongModuleNameThatCouldEvenCauseAnEmptyBindingListToExpandIntoMultipleLine
+  ()
+
+#test preamble full-preamble
+{-# LANGUAGE BangPatterns #-}
+
+{-
+ - Test module
+ -}
+module Test
+  ( test1
+  -- ^ test
+  , test2
+  -- | test
+  , test3
+  , test4
+  , test5
+  , test6
+  , test7
+  , test8
+  , test9
+  , test10
+  )
+where
+
+-- Test
+import Data.List (nub) -- Test
+{- Test -}
+import qualified Data.List as L (foldl') {- Test -}
+
+-- Test
+import Test (test)
 
 ###############################################################################
 ###############################################################################
@@ -1133,4 +1386,3 @@ foo =
 ##           ]
 ##  where
 ##   role = stringProperty "WM_WINDOW_ROLE"
-

src-unittests/TestUtils.hs

@@ -51,11 +51,14 @@ defaultTestConfig = Config
     , _lconfig_indentWhereSpecial        = coerce True
     , _lconfig_indentListSpecial         = coerce True
     , _lconfig_importColumn              = coerce (60 :: Int)
+    , _lconfig_importAsColumn            = coerce (60 :: Int)
     , _lconfig_altChooser                = coerce $ AltChooserBoundedSearch 3
     , _lconfig_columnAlignMode           = coerce (ColumnAlignModeMajority 0.7)
     , _lconfig_alignmentLimit            = coerce (30 :: Int)
     , _lconfig_alignmentBreakOnMultiline = coerce True
     , _lconfig_hangingTypeSignature      = coerce False
+    , _lconfig_reformatModulePreamble    = coerce True
+    , _lconfig_allowSingleLineExportList = coerce True
     }
   , _conf_errorHandling = (_conf_errorHandling staticDefaultConfig)
     { _econf_ExactPrintFallback = coerce ExactPrintFallbackModeNever

src/Language/Haskell/Brittany/Internal.hs

@@ -16,7 +16,7 @@ where
 #include "prelude.inc"
 
 import qualified Language.Haskell.GHC.ExactPrint as ExactPrint
-import qualified Language.Haskell.GHC.ExactPrint.Types as ExactPrint.Types
+import qualified Language.Haskell.GHC.ExactPrint.Types as ExactPrint
 import qualified Language.Haskell.GHC.ExactPrint.Parsers as ExactPrint.Parsers
 
 import           Data.Data
@@ -33,6 +33,7 @@ import           Language.Haskell.Brittany.Internal.LayouterBasics
 
 import           Language.Haskell.Brittany.Internal.Layouters.Type
 import           Language.Haskell.Brittany.Internal.Layouters.Decl
+import           Language.Haskell.Brittany.Internal.Layouters.Module
 import           Language.Haskell.Brittany.Internal.Utils
 import           Language.Haskell.Brittany.Internal.Backend
 import           Language.Haskell.Brittany.Internal.BackendUtils
@@ -132,7 +133,7 @@ parsePrintModule configRaw inputText = runExceptT $ do
 -- can occur.
 pPrintModule
   :: Config
-  -> ExactPrint.Types.Anns
+  -> ExactPrint.Anns
   -> GHC.ParsedSource
   -> ([BrittanyError], TextL.Text)
 pPrintModule conf anns parsedModule =
@@ -160,7 +161,7 @@ pPrintModule conf anns parsedModule =
   in
     tracer $ (errs, Text.Builder.toLazyText out)
   -- unless () $ do
-  --   
+  --
   --   debugStrings `forM_` \s ->
   --     trace s $ return ()
 
@@ -168,7 +169,7 @@ pPrintModule conf anns parsedModule =
 -- if it does not.
 pPrintModuleAndCheck
   :: Config
-  -> ExactPrint.Types.Anns
+  -> ExactPrint.Anns
   -> GHC.ParsedSource
   -> IO ([BrittanyError], TextL.Text)
 pPrintModuleAndCheck conf anns parsedModule = do
@@ -248,33 +249,11 @@ parsePrintModuleTests conf filename input = do
 --         else return $ TextL.toStrict $ Text.Builder.toLazyText out
 
 ppModule :: GenLocated SrcSpan (HsModule RdrName) -> PPM ()
-ppModule lmod@(L loc m@(HsModule _name _exports _imports decls _ _)) = do
-  let emptyModule = L loc m { hsmodDecls = [] }
-  (anns', post) <- do
-    anns <- mAsk
-    -- evil partiality. but rather unlikely.
-    return $ case Map.lookup (ExactPrint.Types.mkAnnKey lmod) anns of
-      Nothing -> (anns, [])
-      Just mAnn ->
-        let modAnnsDp = ExactPrint.Types.annsDP mAnn
-            isWhere (ExactPrint.Types.G AnnWhere) = True
-            isWhere _                             = False
-            isEof (ExactPrint.Types.G AnnEofPos) = True
-            isEof _                              = False
-            whereInd    = List.findIndex (isWhere . fst) modAnnsDp
-            eofInd      = List.findIndex (isEof . fst) modAnnsDp
-            (pre, post) = case (whereInd, eofInd) of
-              (Nothing, Nothing) -> ([], modAnnsDp)
-              (Just i , Nothing) -> List.splitAt (i + 1) modAnnsDp
-              (Nothing, Just _i) -> ([], modAnnsDp)
-              (Just i , Just j ) -> List.splitAt (min (i + 1) j) modAnnsDp
-            mAnn'       = mAnn { ExactPrint.Types.annsDP = pre }
-            anns'       = Map.insert (ExactPrint.Types.mkAnnKey lmod) mAnn' anns
-        in  (anns', post)
-  MultiRWSS.withMultiReader anns' $ processDefault emptyModule
+ppModule lmod@(L _loc _m@(HsModule _name _exports _ decls _ _)) = do
+  post <- ppPreamble lmod
   decls `forM_` \decl -> do
     filteredAnns <- mAsk <&> \annMap ->
-      Map.findWithDefault Map.empty (ExactPrint.Types.mkAnnKey decl) annMap
+      Map.findWithDefault Map.empty (ExactPrint.mkAnnKey decl) annMap
 
     traceIfDumpConf "bridoc annotations filtered/transformed"
                     _dconf_dump_annotations
@@ -287,26 +266,26 @@ ppModule lmod@(L loc m@(HsModule _name _exports _imports decls _ _)) = do
       ppDecl decl
   let finalComments = filter
         ( fst .> \case
-          ExactPrint.Types.AnnComment{} -> True
+          ExactPrint.AnnComment{} -> True
           _                             -> False
         )
         post
   post `forM_` \case
-    (ExactPrint.Types.AnnComment (ExactPrint.Types.Comment cmStr _ _), l) -> do
+    (ExactPrint.AnnComment (ExactPrint.Comment cmStr _ _), l) -> do
       ppmMoveToExactLoc l
       mTell $ Text.Builder.fromString cmStr
-    (ExactPrint.Types.G AnnEofPos, (ExactPrint.Types.DP (eofX, eofY))) ->
+    (ExactPrint.G AnnEofPos, (ExactPrint.DP (eofZ, eofX))) ->
       let
-        folder (acc, _) (kw, ExactPrint.Types.DP (x, y)) = case kw of
-          ExactPrint.Types.AnnComment cm
-            | GHC.RealSrcSpan span <- ExactPrint.Types.commentIdentifier cm
-            -> ( acc + x + GHC.srcSpanEndLine span - GHC.srcSpanStartLine span
-               , y + GHC.srcSpanEndCol span - GHC.srcSpanStartCol span
+        folder (acc, _) (kw, ExactPrint.DP (y, x)) = case kw of
+          ExactPrint.AnnComment cm
+            | GHC.RealSrcSpan span <- ExactPrint.commentIdentifier cm
+            -> ( acc + y + GHC.srcSpanEndLine span - GHC.srcSpanStartLine span
+               , x + GHC.srcSpanEndCol span - GHC.srcSpanStartCol span
                )
-          _ -> (acc + x, y)
-        (cmX, cmY) = foldl' folder (0, 0) finalComments
+          _ -> (acc + y, x)
+        (cmY, cmX) = foldl' folder (0, 0) finalComments
       in
-        ppmMoveToExactLoc $ ExactPrint.Types.DP (eofX - cmX, eofY - cmY)
+        ppmMoveToExactLoc $ ExactPrint.DP (eofZ - cmY, eofX - cmX)
     _ -> return ()
 
 withTransformedAnns :: Data ast => ast -> PPMLocal () -> PPMLocal ()
@@ -341,6 +320,76 @@ ppDecl d@(L loc decl) = case decl of
     layoutBriDoc briDoc
   _ -> briDocMToPPM (briDocByExactNoComment d) >>= layoutBriDoc
 
+-- Prints the information associated with the module annotation
+-- This includes the imports
+ppPreamble :: GenLocated SrcSpan (HsModule RdrName)
+           -> PPM [(ExactPrint.KeywordId, ExactPrint.DeltaPos)]
+ppPreamble lmod@(L loc m@(HsModule _ _ _ _ _ _)) = do
+  filteredAnns <- mAsk <&> \annMap ->
+    Map.findWithDefault Map.empty (ExactPrint.mkAnnKey lmod) annMap
+    -- Since ghc-exactprint adds annotations following (implicit)
+    -- modules to both HsModule and the elements in the module
+    -- this can cause duplication of comments. So strip
+    -- attached annotations that come after the module's where
+    -- from the module node
+  config <- mAsk
+  let shouldReformatPreamble =
+        config & _conf_layout & _lconfig_reformatModulePreamble & confUnpack
+
+  let
+    (filteredAnns', post) =
+      case (ExactPrint.mkAnnKey lmod) `Map.lookup` filteredAnns of
+        Nothing -> (filteredAnns, [])
+        Just mAnn ->
+          let
+            modAnnsDp = ExactPrint.annsDP mAnn
+            isWhere (ExactPrint.G AnnWhere) = True
+            isWhere _                       = False
+            isEof (ExactPrint.G AnnEofPos) = True
+            isEof _                        = False
+            whereInd     = List.findIndex (isWhere . fst) modAnnsDp
+            eofInd       = List.findIndex (isEof . fst) modAnnsDp
+            (pre, post') = case (whereInd, eofInd) of
+              (Nothing, Nothing) -> ([], modAnnsDp)
+              (Just i , Nothing) -> List.splitAt (i + 1) modAnnsDp
+              (Nothing, Just _i) -> ([], modAnnsDp)
+              (Just i , Just j ) -> List.splitAt (min (i + 1) j) modAnnsDp
+            findInitialCommentSize = \case
+              ((ExactPrint.AnnComment cm, ExactPrint.DP (y, _)) : rest) ->
+                let GHC.RealSrcSpan span = ExactPrint.commentIdentifier cm
+                in  y
+                    + GHC.srcSpanEndLine span
+                    - GHC.srcSpanStartLine span
+                    + findInitialCommentSize rest
+              _ -> 0
+            initialCommentSize  = findInitialCommentSize pre
+            fixAbsoluteModuleDP = \case
+              (g@(ExactPrint.G AnnModule), ExactPrint.DP (y, x)) ->
+                (g, ExactPrint.DP (y - initialCommentSize, x))
+              x -> x
+            pre' = if shouldReformatPreamble
+              then map fixAbsoluteModuleDP pre
+              else pre
+            mAnn' = mAnn { ExactPrint.annsDP = pre' }
+            filteredAnns'' =
+              Map.insert (ExactPrint.mkAnnKey lmod) mAnn' filteredAnns
+          in
+            (filteredAnns'', post')
+  traceIfDumpConf "bridoc annotations filtered/transformed"
+                  _dconf_dump_annotations
+    $ annsDoc filteredAnns'
+
+  if shouldReformatPreamble
+    then MultiRWSS.withoutMultiReader $ do
+      MultiRWSS.mPutRawR $ config :+: filteredAnns' :+: HNil
+      withTransformedAnns lmod $ do
+        briDoc <- briDocMToPPM $ layoutModule lmod
+        layoutBriDoc briDoc
+    else
+      let emptyModule = L loc m { hsmodDecls = [] }
+      in  MultiRWSS.withMultiReader filteredAnns' $ processDefault emptyModule
+  return post
+
 _sigHead :: Sig RdrName -> String
 _sigHead = \case
   TypeSig names _ ->
@@ -391,7 +440,7 @@ layoutBriDoc briDoc = do
     -- simpl <- mGet <&> transformToSimple
     -- return simpl
 
-  anns :: ExactPrint.Types.Anns <- mAsk
+  anns :: ExactPrint.Anns <- mAsk
 
   let state = LayoutState
         { _lstate_baseYs           = [0]

src/Language/Haskell/Brittany/Internal/Backend.hs

@@ -250,6 +250,23 @@ layoutBriDocM = \case
             -- layoutMoveToIndentCol y
             layoutWriteAppendMultiline $ Text.pack $ comment
       -- mModify $ \s -> s { _lstate_curYOrAddNewline = Right 0 }
+  BDMoveToKWDP annKey keyword bd -> do
+    mDP <- do
+      state <- mGet
+      let m    = _lstate_comments state
+      let mAnn = ExactPrint.annsDP <$> Map.lookup annKey m
+      let relevant = [ dp
+                     | Just ann <- [mAnn]
+                     , (ExactPrint.Types.G kw1, dp) <- ann
+                     , keyword == kw1
+                     ]
+      pure $ case relevant of
+        [] -> Nothing
+        (dp:_) -> Just dp
+    case mDP of
+      Nothing                           -> pure ()
+      Just (ExactPrint.Types.DP (y, x)) -> layoutMoveToCommentPos y x
+    layoutBriDocM bd
   BDNonBottomSpacing bd -> layoutBriDocM bd
   BDSetParSpacing    bd -> layoutBriDocM bd
   BDForceParSpacing  bd -> layoutBriDocM bd
@@ -282,6 +299,7 @@ briDocLineLength briDoc = flip StateS.evalState False $ rec briDoc
     BDAnnotationPrior _ bd  -> rec bd
     BDAnnotationKW _ _ bd   -> rec bd
     BDAnnotationRest _ bd   -> rec bd
+    BDMoveToKWDP _ _ bd     -> rec bd
     BDLines ls@(_:_)        -> do
       x <- StateS.get
       return $ maximum $ ls <&> \l -> StateS.evalState (rec l) x
@@ -317,6 +335,7 @@ briDocIsMultiLine briDoc = rec briDoc
     BDAnnotationPrior _ bd  -> rec bd
     BDAnnotationKW _ _ bd   -> rec bd
     BDAnnotationRest _ bd   -> rec bd
+    BDMoveToKWDP _ _ bd     -> rec bd
     BDLines (_:_:_)         -> True
     BDLines [_    ]         -> False
     BDLines []              -> error "briDocIsMultiLine BDLines []"

src/Language/Haskell/Brittany/Internal/Config.hs

@@ -65,12 +65,15 @@ staticDefaultConfig = Config
     , _lconfig_indentAmount              = coerce (2 :: Int)
     , _lconfig_indentWhereSpecial        = coerce True
     , _lconfig_indentListSpecial         = coerce True
-    , _lconfig_importColumn              = coerce (60 :: Int)
+    , _lconfig_importColumn              = coerce (50 :: Int)
+    , _lconfig_importAsColumn            = coerce (50 :: Int)
     , _lconfig_altChooser                = coerce (AltChooserBoundedSearch 3)
     , _lconfig_columnAlignMode           = coerce (ColumnAlignModeMajority 0.7)
     , _lconfig_alignmentLimit            = coerce (30 :: Int)
     , _lconfig_alignmentBreakOnMultiline = coerce True
     , _lconfig_hangingTypeSignature      = coerce False
+    , _lconfig_reformatModulePreamble    = coerce True
+    , _lconfig_allowSingleLineExportList = coerce False
     }
   , _conf_errorHandling = ErrorHandlingConfig
     { _econf_produceOutputOnErrors   = coerce False
@@ -111,6 +114,7 @@ configParser = do
   ind                <- addFlagReadParams "" ["indent"] "AMOUNT" (flagHelpStr "spaces per indentation level")
   cols               <- addFlagReadParams "" ["columns"] "AMOUNT" (flagHelpStr "target max columns (80 is an old default for this)")
   importCol          <- addFlagReadParams "" ["import-col"] "N" (flagHelpStr "column to align import lists at")
+  importAsCol        <- addFlagReadParams "" ["import-as-col"] "N" (flagHelpStr "column to qualified-as module names at")
 
   dumpConfig         <- addSimpleBoolFlag "" ["dump-config"] (flagHelp $ parDoc "dump the programs full config (merged commandline + file + defaults)")
   dumpAnnotations    <- addSimpleBoolFlag "" ["dump-annotations"] (flagHelp $ parDoc "dump the full annotations returned by ghc-exactprint")
@@ -160,11 +164,14 @@ configParser = do
       , _lconfig_indentWhereSpecial        = mempty -- falseToNothing _
       , _lconfig_indentListSpecial         = mempty -- falseToNothing _
       , _lconfig_importColumn              = optionConcat importCol
+      , _lconfig_importAsColumn            = optionConcat importAsCol
       , _lconfig_altChooser                = mempty
       , _lconfig_columnAlignMode           = mempty
       , _lconfig_alignmentLimit            = mempty
       , _lconfig_alignmentBreakOnMultiline = mempty
       , _lconfig_hangingTypeSignature      = mempty
+      , _lconfig_reformatModulePreamble    = mempty
+      , _lconfig_allowSingleLineExportList = mempty
       }
     , _conf_errorHandling = ErrorHandlingConfig
       { _econf_produceOutputOnErrors   = wrapLast $ falseToNothing outputOnErrors

src/Language/Haskell/Brittany/Internal/Config/Types.hs

@@ -53,7 +53,12 @@ data CLayoutConfig f = LayoutConfig
   , _lconfig_indentListSpecial  :: f (Last Bool) -- use some special indentation for ","
                                                  -- when creating zero-indentation
                                                  -- multi-line list literals.
-  , _lconfig_importColumn :: f (Last Int)
+  , _lconfig_importColumn    :: f (Last Int)
+    -- ^ for import statement layouting, column at which to align the
+    -- elements to be imported from a module.
+  , _lconfig_importAsColumn  :: f (Last Int)
+    -- ^ for import statement layouting, column at which put the module's
+    -- "as" name (which also affects the positioning of the "as" keyword).
   , _lconfig_altChooser      :: f (Last AltChooser)
   , _lconfig_columnAlignMode :: f (Last ColumnAlignMode)
   , _lconfig_alignmentLimit  :: f (Last Int)
@@ -84,6 +89,21 @@ data CLayoutConfig f = LayoutConfig
     --   -> SomeLongStuff
     -- As usual for hanging indentation, the result will be
     -- context-sensitive (in the function name).
+  , _lconfig_reformatModulePreamble :: f (Last Bool)
+    -- whether the module preamble/header (module keyword, name, export list,
+    -- import statements) are reformatted. If false, only the elements of the
+    -- module (everything past the "where") are reformatted.
+  , _lconfig_allowSingleLineExportList :: f (Last Bool)
+    -- if true, and it fits in a single line, and there are no comments in the
+    -- export list, the following layout will be used:
+    -- > module MyModule (abc, def) where
+    -- > [stuff]
+    -- otherwise, the multi-line version is used:
+    -- > module MyModule
+    -- >   ( abc
+    -- >   , def
+    -- >   )
+    -- > where
   }
   deriving (Generic)
 

src/Language/Haskell/Brittany/Internal/LayouterBasics.hs

@@ -17,6 +17,7 @@ module Language.Haskell.Brittany.Internal.LayouterBasics
   , docSeq
   , docPar
   , docNodeAnnKW
+  , docNodeMoveToKWDP
   , docWrapNode
   , docWrapNodePrior
   , docWrapNodeRest
@@ -30,6 +31,7 @@ module Language.Haskell.Brittany.Internal.LayouterBasics
   , docAnnotationPrior
   , docAnnotationKW
   , docAnnotationRest
+  , docMoveToKWDP
   , docNonBottomSpacing
   , docSetParSpacing
   , docForceParSpacing
@@ -43,6 +45,7 @@ module Language.Haskell.Brittany.Internal.LayouterBasics
   , appSep
   , docCommaSep
   , docParenLSep
+  , docParenR
   , docTick
   , spacifyDocs
   , briDocMToPPM
@@ -462,6 +465,13 @@ docAnnotationKW
   -> ToBriDocM BriDocNumbered
 docAnnotationKW annKey kw bdm = allocateNode . BDFAnnotationKW annKey kw =<< bdm
 
+docMoveToKWDP
+  :: AnnKey
+  -> AnnKeywordId
+  -> ToBriDocM BriDocNumbered
+  -> ToBriDocM BriDocNumbered
+docMoveToKWDP annKey kw bdm = allocateNode . BDFMoveToKWDP annKey kw =<< bdm
+
 docAnnotationRest
   :: AnnKey -> ToBriDocM BriDocNumbered -> ToBriDocM BriDocNumbered
 docAnnotationRest annKey bdm = allocateNode . BDFAnnotationRest annKey =<< bdm
@@ -487,6 +497,9 @@ docCommaSep = appSep $ docLit $ Text.pack ","
 docParenLSep :: ToBriDocM BriDocNumbered
 docParenLSep = appSep $ docLit $ Text.pack "("
 
+docParenR :: ToBriDocM BriDocNumbered
+docParenR = docLit $ Text.pack ")"
+
 docTick :: ToBriDocM BriDocNumbered
 docTick = docLit $ Text.pack "'"
 
@@ -499,6 +512,15 @@ docNodeAnnKW
 docNodeAnnKW ast kw bdm =
   docAnnotationKW (ExactPrint.Types.mkAnnKey ast) kw bdm
 
+docNodeMoveToKWDP
+  :: Data.Data.Data ast
+  => Located ast
+  -> AnnKeywordId
+  -> ToBriDocM BriDocNumbered
+  -> ToBriDocM BriDocNumbered
+docNodeMoveToKWDP ast kw bdm =
+  docMoveToKWDP (ExactPrint.Types.mkAnnKey ast) kw bdm
+
 class DocWrapable a where
   docWrapNode :: ( Data.Data.Data ast)
               => Located ast

src/Language/Haskell/Brittany/Internal/Layouters/IE.hs

@@ -0,0 +1,145 @@
+module Language.Haskell.Brittany.Internal.Layouters.IE
+  ( layoutIE
+  , layoutLLIEs
+  , layoutAnnAndSepLLIEs
+  )
+where
+
+#include "prelude.inc"
+
+import           Language.Haskell.Brittany.Internal.Types
+import           Language.Haskell.Brittany.Internal.LayouterBasics
+import           Language.Haskell.Brittany.Internal.Config.Types
+
+import           RdrName (RdrName(..))
+import           GHC     ( unLoc
+                         , runGhc
+                         , GenLocated(L)
+                         , moduleNameString
+                         , AnnKeywordId(..)
+                         , Located
+                         )
+import           HsSyn
+import           Name
+import           HsImpExp
+import           FieldLabel
+import qualified FastString
+import           BasicTypes
+
+import           Language.Haskell.Brittany.Internal.Utils
+
+
+
+#if MIN_VERSION_ghc(8,2,0)
+prepareName :: LIEWrappedName name -> Located name
+prepareName = ieLWrappedName
+#else
+prepareName :: Located name -> Located name
+prepareName = id
+#endif
+
+layoutIE :: ToBriDoc IE
+layoutIE lie@(L _ ie) = docWrapNode lie $ case ie of
+  IEVar      _                     -> ien
+  IEThingAbs _                     -> ien
+  IEThingAll _                     -> docSeq [ien, docLit $ Text.pack "(..)"]
+  IEThingWith _ (IEWildcard _) _ _ -> docSeq [ien, docLit $ Text.pack "(..)"]
+  IEThingWith _ _ ns _ -> do
+    hasComments <- hasAnyCommentsBelow lie
+    docAltFilter
+      [ ( not hasComments
+        , docSeq
+        $  [ien, docLit $ Text.pack "("]
+        ++ intersperse docCommaSep (map nameDoc ns)
+        ++ [docParenR]
+        )
+      , (otherwise
+        , docAddBaseY BrIndentRegular
+        $ docPar ien (layoutItems (splitFirstLast ns))
+        )
+      ]
+   where
+    nameDoc = (docLit =<<) . lrdrNameToTextAnn . prepareName
+    layoutItem n = docSeq [docCommaSep, docWrapNode n $ nameDoc n]
+    layoutItems FirstLastEmpty =
+      docSetBaseY $
+        docLines [docSeq [docParenLSep, docWrapNodeRest lie docEmpty]
+                 ,docParenR
+                 ]
+    layoutItems (FirstLastSingleton n) =
+      docSetBaseY $ docLines
+        [docSeq [docParenLSep, docWrapNodeRest lie $ nameDoc n], docParenR]
+    layoutItems (FirstLast n1 nMs nN)  =
+      docSetBaseY $ docLines $
+         [docSeq [docParenLSep, docWrapNode n1 $ nameDoc n1]]
+         ++ map layoutItem nMs
+         ++ [ docSeq [docCommaSep, docWrapNodeRest lie $ nameDoc nN]
+            , docParenR
+            ]
+  IEModuleContents n -> docSeq
+    [ docLit $ Text.pack "module"
+    , docSeparator
+    , docLit . Text.pack . moduleNameString $ unLoc n
+    ]
+  _ -> docEmpty
+  where ien = docLit =<< lrdrNameToTextAnn (ieName <$> lie)
+
+-- Helper function to deal with Located lists of LIEs.
+-- In particular this will also associate documentation
+-- from the located list that actually belongs to the last IE.
+-- It also adds docCommaSep to all but the first element
+-- This configuration allows both vertical and horizontal
+-- handling of the resulting list. Adding parens is
+-- left to the caller since that is context sensitive
+layoutAnnAndSepLLIEs
+  :: Located [LIE RdrName] -> ToBriDocM [ToBriDocM BriDocNumbered]
+layoutAnnAndSepLLIEs llies@(L _ lies) = do
+  let makeIENode ie = docSeq [docCommaSep, ie]
+  let ieDocs = layoutIE <$> lies
+  ieCommaDocs <-
+    docWrapNodeRest llies $ sequence $ case splitFirstLast ieDocs of
+      FirstLastEmpty        -> []
+      FirstLastSingleton ie -> [ie]
+      FirstLast ie1 ieMs ieN ->
+        [ie1] ++ map makeIENode ieMs ++ [makeIENode ieN]
+  pure $ fmap pure ieCommaDocs -- returned shared nodes
+
+-- Builds a complete layout for the given located
+-- list of LIEs. The layout provides two alternatives:
+-- (item, item, ..., item)
+-- ( item
+-- , item
+-- ...
+-- , item
+-- )
+-- If the llies contains comments the list will
+-- always expand over multiple lines, even when empty:
+-- () -- no comments
+-- ( -- a comment
+-- )
+layoutLLIEs :: Bool -> Located [LIE RdrName] -> ToBriDocM BriDocNumbered
+layoutLLIEs enableSingleline llies = do
+  ieDs        <- layoutAnnAndSepLLIEs llies
+  hasComments <- hasAnyCommentsBelow llies
+  case ieDs of
+    [] -> docAltFilter
+      [ (not hasComments, docLit $ Text.pack "()")
+      , ( hasComments
+        , docPar (docSeq [docParenLSep, docWrapNodeRest llies docEmpty])
+                 docParenR
+        )
+      ]
+    (ieDsH:ieDsT) -> docAltFilter
+      [ ( not hasComments && enableSingleline
+        , docSeq
+        $  [docLit (Text.pack "(")]
+        ++ (docForceSingleline <$> ieDs)
+        ++ [docParenR]
+        )
+      , ( otherwise
+        , docPar (docSetBaseY $ docSeq [docParenLSep, ieDsH])
+        $  docLines
+        $  ieDsT
+        ++ [docParenR]
+        )
+      ]

src/Language/Haskell/Brittany/Internal/Layouters/Import.hs

@@ -0,0 +1,147 @@
+module Language.Haskell.Brittany.Internal.Layouters.Import (layoutImport) where
+
+#include "prelude.inc"
+
+import           Language.Haskell.Brittany.Internal.Types
+import           Language.Haskell.Brittany.Internal.LayouterBasics
+import           Language.Haskell.Brittany.Internal.Layouters.IE
+import           Language.Haskell.Brittany.Internal.Config.Types
+
+import           RdrName                                  ( RdrName(..) )
+import           GHC                                      ( unLoc
+                                                          , GenLocated(L)
+                                                          , moduleNameString
+                                                          , Located
+                                                          )
+import           HsSyn
+import           Name
+import           FieldLabel
+import qualified FastString
+import           BasicTypes
+
+import           Language.Haskell.Brittany.Internal.Utils
+
+
+
+#if MIN_VERSION_ghc(8,2,0)
+prepPkg :: SourceText -> String
+prepPkg rawN = case rawN of
+  SourceText n -> n
+  -- This would be odd to encounter and the
+  -- result will most certainly be wrong
+  NoSourceText -> ""
+#else
+prepPkg :: String -> String
+prepPkg = id
+#endif
+#if MIN_VERSION_ghc(8,2,0)
+prepModName :: Located e -> e
+prepModName = unLoc
+#else
+prepModName :: e -> e
+prepModName = id
+#endif
+
+layoutImport :: ToBriDoc ImportDecl
+layoutImport limportD@(L _ importD) = docWrapNode limportD $ case importD of
+  ImportDecl _ (L _ modName) pkg src safe q False mas mllies -> do
+    importCol <- mAsk <&> _conf_layout .> _lconfig_importColumn .> confUnpack
+    importAsCol <- mAsk <&> _conf_layout .> _lconfig_importAsColumn .> confUnpack
+    indentPolicy <- mAsk <&>  _conf_layout .> _lconfig_indentPolicy .> confUnpack
+    let
+      compact  = indentPolicy == IndentPolicyLeft
+      modNameT = Text.pack $ moduleNameString modName
+      pkgNameT = Text.pack . prepPkg . sl_st <$> pkg
+      masT     = Text.pack . moduleNameString . prepModName <$> mas
+      hiding   = maybe False fst mllies
+      minQLength = length "import qualified "
+      qLengthReal =
+        let qualifiedPart = if q then length "qualified " else 0
+            safePart      = if safe then length "safe " else 0
+            pkgPart       = maybe 0 ((+ 1) . Text.length) pkgNameT
+            srcPart       = if src then length "{-# SOURCE #-} " else 0
+        in  length "import " + srcPart + safePart + qualifiedPart + pkgPart
+      qLength          = max minQLength qLengthReal
+      -- Cost in columns of importColumn
+      asCost           = length "as "
+      bindingCost      = if hiding then length "hiding ( " else length "( "
+      nameCost         = Text.length modNameT + qLength
+      importQualifiers = docSeq
+        [ appSep $ docLit $ Text.pack "import"
+        , if src then appSep $ docLit $ Text.pack "{-# SOURCE #-}" else docEmpty
+        , if safe then appSep $ docLit $ Text.pack "safe" else docEmpty
+        , if q then appSep $ docLit $ Text.pack "qualified" else docEmpty
+        , maybe docEmpty (appSep . docLit) pkgNameT
+        ]
+      indentName =
+        if compact then id else docEnsureIndent (BrIndentSpecial qLength)
+      modNameD =
+        indentName $ appSep $ docLit modNameT
+      hidDoc =
+        if hiding then appSep $ docLit $ Text.pack "hiding" else docEmpty
+      importHead = docSeq [importQualifiers, modNameD]
+      bindingsD  = case mllies of
+        Nothing -> docEmpty
+        Just (_, llies) -> do
+          hasComments <- hasAnyCommentsBelow llies
+          if compact
+          then docSeq [hidDoc, layoutLLIEs True llies]
+          else do
+            ieDs <- layoutAnnAndSepLLIEs llies
+            docWrapNodeRest llies $ case ieDs of
+              -- ..[hiding].( )
+              [] -> if hasComments
+                then docPar
+                  (docSeq [hidDoc, docParenLSep, docWrapNode llies docEmpty])
+                  docParenR
+                else docSeq [hidDoc, docParenLSep, docSeparator, docParenR]
+                -- ..[hiding].( b )
+              [ieD] -> docAltFilter
+                [ ( not hasComments
+                  , docSeq
+                    [ hidDoc
+                    , docParenLSep
+                    , docForceSingleline $ ieD
+                    , docSeparator
+                    , docParenR
+                    ]
+                  )
+                , ( otherwise
+                  , docPar
+                    (docSeq [hidDoc, docParenLSep, docNonBottomSpacing ieD])
+                    docParenR
+                  )
+                ]
+                -- ..[hiding].( b
+                --            , b'
+                --            )
+              (ieD:ieDs') ->
+                docPar (docSeq [hidDoc, docSetBaseY $ docSeq [docParenLSep, ieD]])
+                  $  docLines
+                  $  ieDs'
+                  ++ [docParenR]
+      bindingLine =
+        docEnsureIndent (BrIndentSpecial (importCol - bindingCost)) bindingsD
+      makeAsDoc asT =
+        docSeq [appSep $ docLit $ Text.pack "as", appSep $ docLit asT]
+    if compact
+    then
+      let asDoc = maybe docEmpty makeAsDoc masT
+      in docAlt
+        [ docForceSingleline $ docSeq [importHead, asDoc, bindingsD]
+        , docAddBaseY BrIndentRegular $
+            docPar (docSeq [importHead, asDoc]) bindingsD
+        ]
+    else
+      case masT of
+        Just n | enoughRoom -> docLines [docSeq [importHead, asDoc], bindingLine]
+               | otherwise  -> docLines [importHead, asDoc, bindingLine]
+         where
+          enoughRoom = nameCost < importAsCol - asCost
+          asDoc =
+            docEnsureIndent (BrIndentSpecial (importAsCol - asCost))
+              $ makeAsDoc n
+        Nothing | enoughRoom -> docSeq [importHead, bindingLine]
+                | otherwise  -> docLines [importHead, bindingLine]
+          where enoughRoom = nameCost < importCol - bindingCost
+  _ -> docEmpty

src/Language/Haskell/Brittany/Internal/Layouters/Module.hs

@@ -0,0 +1,62 @@
+module Language.Haskell.Brittany.Internal.Layouters.Module (layoutModule) where
+
+#include "prelude.inc"
+
+import           Language.Haskell.Brittany.Internal.Types
+import           Language.Haskell.Brittany.Internal.LayouterBasics
+import           Language.Haskell.Brittany.Internal.Layouters.IE
+import           Language.Haskell.Brittany.Internal.Layouters.Import
+import           Language.Haskell.Brittany.Internal.Config.Types
+
+import           RdrName (RdrName(..))
+import GHC (unLoc, runGhc, GenLocated(L), moduleNameString, AnnKeywordId(..))
+import           HsSyn
+import           Name
+import           HsImpExp
+import           FieldLabel
+import qualified FastString
+import           BasicTypes
+import           Language.Haskell.GHC.ExactPrint as ExactPrint
+import           Language.Haskell.GHC.ExactPrint.Types as ExactPrint.Types
+
+import           Language.Haskell.Brittany.Internal.Utils
+
+
+
+layoutModule :: ToBriDoc HsModule
+layoutModule lmod@(L _ mod') = case mod' of
+    -- Implicit module Main
+  HsModule Nothing  _   imports _ _ _ -> docLines $ map layoutImport imports
+  HsModule (Just n) les imports _ _ _ -> do
+    let tn = Text.pack $ moduleNameString $ unLoc n
+    allowSingleLineExportList <- mAsk
+      <&> _conf_layout
+      .>  _lconfig_allowSingleLineExportList
+      .>  confUnpack
+    docLines
+      $ docSeq
+          [ docNodeAnnKW lmod Nothing docEmpty
+             -- A pseudo node that serves merely to force documentation
+             -- before the node
+          , docNodeMoveToKWDP lmod AnnModule $ docAltFilter
+            [ (,) allowSingleLineExportList $ docForceSingleline $ docSeq
+                   [ appSep $ docLit $ Text.pack "module"
+                   , appSep $ docLit tn
+                   , docWrapNode lmod $ appSep $ case les of
+                     Nothing -> docEmpty
+                     Just x  -> layoutLLIEs True x
+                   , docLit $ Text.pack "where"
+                   ]
+            , (,) otherwise $ docLines
+                   [ docAddBaseY BrIndentRegular $ docPar
+                     (docSeq [appSep $ docLit $ Text.pack "module", docLit tn]
+                     )
+                     (docWrapNode lmod $ case les of
+                       Nothing -> docEmpty
+                       Just x  -> layoutLLIEs False x
+                     )
+                   , docLit $ Text.pack "where"
+                   ]
+            ]
+          ]
+      : map layoutImport imports

src/Language/Haskell/Brittany/Internal/Transformations/Alt.hs

@@ -301,6 +301,8 @@ transformAlts briDoc =
           reWrap . BDFAnnotationRest annKey <$> rec bd
         BDFAnnotationKW annKey kw bd ->
           reWrap . BDFAnnotationKW annKey kw <$> rec bd
+        BDFMoveToKWDP annKey kw bd ->
+          reWrap . BDFMoveToKWDP annKey kw <$> rec bd
         BDFLines [] -> return $ reWrap BDFEmpty -- evil transformation. or harmless.
         BDFLines (l:lr) -> do
           ind <- _acp_indent <$> mGet
@@ -319,11 +321,16 @@ transformAlts briDoc =
                 BrIndentNone -> 0
                 BrIndentRegular -> indAmount
                 BrIndentSpecial i -> i
-          mSet $ acp { _acp_indentPrep = 0 -- TODO: i am not sure this is valid,
-                                           -- in general.
-                     , _acp_indent = _acp_indent acp + indAdd
-                     , _acp_line = _acp_line acp + indAdd
-                     }
+          mSet $ acp
+            { _acp_indentPrep = 0
+              -- TODO: i am not sure this is valid, in general.
+            , _acp_indent = _acp_indent acp + indAdd
+            , _acp_line = max (_acp_line acp) (_acp_indent acp + indAdd)
+              -- we cannot use just _acp_line acp + indAdd because of the case
+              -- where there are multiple BDFEnsureIndents in the same line.
+              -- Then, the actual indentation is relative to the current
+              -- indentation, not the current cursor position.
+            }
           r <- rec bd
           acp' <- mGet
           mSet $ acp' { _acp_indent = _acp_indent acp }
@@ -455,6 +462,7 @@ getSpacing !bridoc = rec bridoc
       BDFAnnotationPrior _annKey bd -> rec bd
       BDFAnnotationKW _annKey _kw bd -> rec bd
       BDFAnnotationRest  _annKey bd -> rec bd
+      BDFMoveToKWDP _annKey _kw bd -> rec bd
       BDFLines [] -> return
         $ LineModeValid
         $ VerticalSpacing 0 VerticalSpacingParNone False
@@ -700,6 +708,7 @@ getSpacings limit bridoc = preFilterLimit <$> rec bridoc
         BDFAnnotationPrior _annKey bd -> rec bd
         BDFAnnotationKW _annKey _kw bd -> rec bd
         BDFAnnotationRest  _annKey bd -> rec bd
+        BDFMoveToKWDP _annKey _kw bd -> rec bd
         BDFLines [] -> return $ [VerticalSpacing 0 VerticalSpacingParNone False]
         BDFLines ls@(_:_) -> do
           -- we simply assume that lines is only used "properly", i.e. in

src/Language/Haskell/Brittany/Internal/Transformations/Columns.hs

@@ -128,6 +128,7 @@ transformSimplifyColumns = Uniplate.rewrite $ \case
   BDAnnotationPrior{} -> Nothing
   BDAnnotationKW{}    -> Nothing
   BDAnnotationRest{}  -> Nothing
+  BDMoveToKWDP{}      -> Nothing
   BDEnsureIndent{}    -> Nothing
   BDSetParSpacing{}   -> Nothing
   BDForceParSpacing{} -> Nothing

src/Language/Haskell/Brittany/Internal/Types.hs

@@ -178,6 +178,7 @@ data ColSig
   | ColTuple
   | ColTuples
   | ColOpPrefix -- merge with ColList ? other stuff?
+  | ColImport
 
   -- TODO
   deriving (Eq, Ord, Data.Data.Data, Show)
@@ -232,6 +233,7 @@ data BriDoc
   | BDAnnotationPrior AnnKey BriDoc
   | BDAnnotationKW AnnKey (Maybe AnnKeywordId) BriDoc
   | BDAnnotationRest  AnnKey BriDoc
+  | BDMoveToKWDP AnnKey AnnKeywordId BriDoc
   | BDLines [BriDoc]
   | BDEnsureIndent BrIndent BriDoc
   -- the following constructors are only relevant for the alt transformation
@@ -277,6 +279,7 @@ data BriDocF f
   | BDFAnnotationPrior AnnKey (f (BriDocF f))
   | BDFAnnotationKW AnnKey (Maybe AnnKeywordId) (f (BriDocF f))
   | BDFAnnotationRest  AnnKey (f (BriDocF f))
+  | BDFMoveToKWDP AnnKey AnnKeywordId (f (BriDocF f))
   | BDFLines [(f (BriDocF f))]
   | BDFEnsureIndent BrIndent (f (BriDocF f))
   | BDFForceMultiline (f (BriDocF f))
@@ -310,6 +313,7 @@ instance Uniplate.Uniplate BriDoc where
   uniplate (BDAnnotationPrior annKey bd) = plate BDAnnotationPrior |- annKey |* bd
   uniplate (BDAnnotationKW annKey kw bd) = plate BDAnnotationKW |- annKey |- kw |* bd
   uniplate (BDAnnotationRest annKey bd)  = plate BDAnnotationRest |- annKey |* bd
+  uniplate (BDMoveToKWDP annKey kw bd)   = plate BDMoveToKWDP |- annKey |- kw |* bd
   uniplate (BDLines lines)               = plate BDLines ||* lines
   uniplate (BDEnsureIndent ind bd)       = plate BDEnsureIndent |- ind |* bd
   uniplate (BDForceMultiline   bd)       = plate BDForceMultiline |* bd
@@ -341,6 +345,7 @@ unwrapBriDocNumbered tpl = case snd tpl of
   BDFAnnotationPrior annKey bd -> BDAnnotationPrior annKey $ rec bd
   BDFAnnotationKW annKey kw bd -> BDAnnotationKW annKey kw $ rec bd
   BDFAnnotationRest annKey bd  -> BDAnnotationRest annKey $ rec bd
+  BDFMoveToKWDP annKey kw bd   -> BDMoveToKWDP annKey kw $ rec bd
   BDFLines lines               -> BDLines $ rec <$> lines
   BDFEnsureIndent ind bd       -> BDEnsureIndent ind $ rec bd
   BDFForceMultiline   bd       -> BDForceMultiline $ rec bd
@@ -376,6 +381,7 @@ briDocSeqSpine = \case
   BDAnnotationPrior _annKey bd  -> briDocSeqSpine bd
   BDAnnotationKW _annKey _kw bd -> briDocSeqSpine bd
   BDAnnotationRest _annKey bd   -> briDocSeqSpine bd
+  BDMoveToKWDP _annKey _kw bd   -> briDocSeqSpine bd
   BDLines lines                 -> foldl' (\(!()) -> briDocSeqSpine) () lines
   BDEnsureIndent _ind bd        -> briDocSeqSpine bd
   BDForceMultiline   bd         -> briDocSeqSpine bd