Use ghc-lib-parser rather than haskell-src-exts

This patch swaps out the parsing library from `haskell-src-exts` to
`ghc-lib-parser`, which gives us better compatibility with GHC.

Because almost every module heavily used the Haskell AST provided by
`haskell-src-exts`, this was a huge effort and it would not have been possible
without Felix Mulder doing an initial port, GSoC student Beatrice Vergani
porting several other steps, and Łukasz Gołębiewski and Paweł Szulc who helped
me finish up things in the home stretch.

I've generally tried to keep styling 100% compatible with what was there before,
but some issues may have unintentionally slipped in so please report those.

This introduces one new import styling contributed by Felix: when wrapping
import lists over multiple lines, you can repeat the module name, e.g.:

    import Control.Monad.Except as X (ExceptT (..), MonadError (..), liftEither)
    import Control.Monad.Except as X (runExceptT, withExceptT)

This is activated by using `import_align: repeat`.

Secondly, a new Step was added, `module_header`, which formats the export list
of a module, including the trailing `where` clause.  Details for this new step
can be found in the `data/stylish-haskell.yaml`.

Co-Authored-By: Beatrice Vergani <beatrice.vergani11@gmail.com>
Co-Authored-By: Paweł Szulc <paul.szulc@gmail.com>
Co-Authored-By: Łukasz Gołębiewski <lukasz.golebiewski@gmail.com>
Co-Authored-By: Felix Mulder <felix.mulder@klarna.com>

1 files changed, 687 insertions, 7 deletions

diff --git a/tests/Language/Haskell/Stylish/Step/Data/Tests.hs b/tests/Language/Haskell/Stylish/Step/Data/Tests.hs
index b43e6dc..4357af6 100644
--- a/tests/Language/Haskell/Stylish/Step/Data/Tests.hs
+++ b/tests/Language/Haskell/Stylish/Step/Data/Tests.hs
@@ -35,6 +35,36 @@ tests = testGroup "Language.Haskell.Stylish.Step.Data.Tests"
     , testCase "case 22" case22
     , testCase "case 23" case23
     , testCase "case 24" case24
+    , testCase "case 25" case25
+    , testCase "case 26" case26
+    , testCase "case 27" case27
+    , testCase "case 28" case28
+    , testCase "case 29" case29
+    , testCase "case 30" case30
+    , testCase "case 31" case31
+    , testCase "case 32" case32
+    , testCase "case 33" case33
+    , testCase "case 34" case34
+    , testCase "case 35" case35
+    , testCase "case 36" case36
+    , testCase "case 37" case37
+    , testCase "case 38" case38
+    , testCase "case 39" case39
+    , testCase "case 40" case40
+    , testCase "case 41" case41
+    , testCase "case 42" case42
+    , testCase "case 43" case43
+    , testCase "case 44" case44
+    , testCase "case 45" case45
+    , testCase "case 46" case46
+    , testCase "case 47" case47
+    , testCase "case 48" case48
+    , testCase "case 49" case49
+    , testCase "case 50" case50
+    , testCase "case 51" case51
+    , testCase "case 52" case52
+    , testCase "case 53" case53
+    , testCase "case 54" case54
     ]
 
 case00 :: Assertion
@@ -165,7 +195,7 @@ case07 = expected @=? testStep (step sameSameStyle) input
     expected = input
 
 case08 :: Assertion
-case08 = input @=? testStep (step sameSameStyle) input
+case08 = expected @=? testStep (step sameSameStyle) input
   where
     input = unlines
       [ "module Herp where"
@@ -173,6 +203,11 @@ case08 = input @=? testStep (step sameSameStyle) input
       , "data Phantom a ="
       , "  Phantom"
       ]
+    expected = unlines
+      [ "module Herp where"
+      , ""
+      , "data Phantom a = Phantom"
+      ]
 
 case09 :: Assertion
 case09 = expected @=? testStep (step indentIndentStyle4) input
@@ -333,7 +368,8 @@ case16 = expected @=? testStep (step indentIndentStyle) input
       , ""
       , "data Foo"
       , "  = Foo"
-      , "      { a :: Int -- ^ comment"
+      , "      { a :: Int"
+      , "        -- ^ comment"
       , "      }"
       ]
 
@@ -520,17 +556,661 @@ case24 = expected @=? testStep (step indentIndentStyle) input
        , "  deriving (ToJSON)"
        ]
 
+case25 :: Assertion
+case25 = expected @=? testStep (step indentIndentStyle { cBreakSingleConstructors = False }) input
+  where
+    input = unlines
+       [ "data Foo a"
+       , "  = Foo { a :: Int,"
+       , "          a2 :: String"
+       , "          -- ^ some haddock"
+       , "        }"
+       , "  deriving (Eq, Show)"
+       , "  deriving (ToJSON)"
+       ]
+
+    expected = unlines
+       [ "data Foo a = Foo"
+       , "  { a :: Int"
+       , "  , a2 :: String"
+       , "    -- ^ some haddock"
+       , "  }"
+       , "  deriving (Eq, Show)"
+       , "  deriving (ToJSON)"
+       ]
+
+case26 :: Assertion
+case26 = expected @=? testStep (step indentIndentStyle) input
+  where
+    input = unlines
+      [ "module Herp where"
+      , ""
+      , "data Foo = Foo { a :: Int } deriving (FromJSON) via Bla Foo"
+      ]
+
+    expected = unlines
+       [ "module Herp where"
+       , ""
+       , "data Foo"
+       , "  = Foo"
+       , "      { a :: Int"
+       , "      }"
+       , "  deriving (FromJSON) via Bla Foo"
+       ]
+
+case27 :: Assertion
+case27 = expected @=? testStep (step sameIndentStyle { cBreakEnums = True }) input
+  where
+    input = unlines
+      [ "module Herp where"
+      , ""
+      , "data Foo = Foo | Bar | Baz deriving (Eq, Show)"
+      ]
+
+    expected = unlines
+      [ "module Herp where"
+      , ""
+      , "data Foo"
+      , "  = Foo"
+      , "  | Bar"
+      , "  | Baz"
+      , "  deriving (Eq, Show)"
+      ]
+
+case28 :: Assertion
+case28 = expected @=? testStep (step sameIndentStyle { cBreakEnums = True }) input
+  where
+    input = unlines
+      [ "module Some.Types where"
+      , ""
+      , "newtype BankCode = BankCode {"
+      , "    unBankCode :: Text"
+      , "  }"
+      , "  deriving stock (Generic, Eq, Show)"
+      , "  deriving anyclass (Newtype)"
+      , ""
+      , "newtype CheckDigit = CheckDigit { unCheckDigit :: Text }"
+      , "  deriving stock (Generic, Eq, Show)"
+      , "  deriving anyclass (Newtype)"
+      , ""
+      , "newtype WrappedInt = WrappedInt Int"
+      , "  deriving stock (Generic, Eq, Show)"
+      , "  deriving anyclass (Newtype)"
+      , ""
+      , "data MandateStatus"
+      , "  = Approved"
+      , "  | Failed"
+      , "  | UserCanceled"
+      , "  | Inactive"
+      , "  deriving stock (Generic, Show, Eq, Enum, Bounded)"
+      , "  deriving (ToJSON, FromJSON) via SnakeCaseCapsEnumEncoding MandateStatus"
+      ]
+
+    expected = unlines
+      [ "module Some.Types where"
+      , ""
+      , "newtype BankCode = BankCode { unBankCode :: Text }"
+      , "  deriving stock (Eq, Generic, Show)"
+      , "  deriving anyclass (Newtype)"
+      , ""
+      , "newtype CheckDigit = CheckDigit { unCheckDigit :: Text }"
+      , "  deriving stock (Eq, Generic, Show)"
+      , "  deriving anyclass (Newtype)"
+      , ""
+      , "newtype WrappedInt = WrappedInt Int"
+      , "  deriving stock (Eq, Generic, Show)"
+      , "  deriving anyclass (Newtype)"
+      , ""
+      , "data MandateStatus"
+      , "  = Approved"
+      , "  | Failed"
+      , "  | UserCanceled"
+      , "  | Inactive"
+      , "  deriving stock (Bounded, Enum, Eq, Generic, Show)"
+      , "  deriving (FromJSON, ToJSON) via SnakeCaseCapsEnumEncoding MandateStatus"
+      ]
+
+case29 :: Assertion
+case29 = expected @=? testStep (step sameIndentStyle) input
+  where
+    input = unlines
+      [ "module Some.Types where"
+      , ""
+      , "data NonEmpty a"
+      , "  = a :| [a]"
+      ]
+
+    expected = unlines
+      [ "module Some.Types where"
+      , ""
+      , "data NonEmpty a = a :| [a]"
+      ]
+
+case30 :: Assertion
+case30 = expected @=? testStep (step sameIndentStyle { cBreakEnums = True }) input
+  where
+    expected = input
+    input = unlines
+      [ "data ReasonCode"
+      , "  = MissingTenantId"
+      , "  -- Transaction errors:"
+      , "  | TransactionDoesNotExist"
+      , "  | TransactionAlreadyExists"
+      , "  -- Engine errors:"
+      , "  | EnginePersistenceError"
+      , "  | EngineValidationError"
+      , "  -- | Transaction was created in Info mode"
+      , "  | RegisteredByNetworkEngine"
+      , "  -- | Transaction was created in Routing mode"
+      , "  | SentToNetworkEngine"
+      , "  -- Network connection reasons:"
+      , "  | SentToNetworkConnection"
+      , "  | ReceivedByNetworkConnection"
+      , "  | ValidatedByNetworkConnection"
+      ]
+
+
+case31 :: Assertion
+case31 = expected @=? testStep (step indentIndentStyle { cBreakEnums = True }) input
+  where
+    expected = input
+    input = unlines
+      [ "data ConfiguredLogger"
+      , "  -- | Logs to file"
+      , "  = LogTo FilePath"
+      , "  -- | Logs to stdout"
+      , "  | LogToConsole"
+      , "  -- | No logging, discards all messages"
+      , "  | NoLogging"
+      , "  deriving stock (Generic, Show)"
+      ]
+
+case32 :: Assertion
+case32 = expected @=? testStep (step indentIndentStyle { cBreakEnums = True }) input
+  where
+    expected = input
+    input = unlines
+      [ "data RejectionReason"
+      , "  -- InvalidState"
+      , "  = CancellationFailed"
+      , "  | TotalAmountConfirmationInvalid"
+      , "  -- InvalidApiUsage"
+      , "  | AccessTokenNotActive"
+      , "  | VersionNotFound"
+      , "  -- ValidationFailed"
+      , "  | BankAccountExists"
+      , "  deriving stock (Eq, Generic, Show)"
+      , "  deriving (FromJSON, ToJSON) via SnakeCaseLowercaseEnumEncoding RejectionReason"
+      ]
+
+case33 :: Assertion
+case33 = expected @=? testStep (step indentIndentStyle { cBreakEnums = True, cBreakSingleConstructors = False }) input
+  where
+    input = unlines
+      [ "module Some.Types where"
+      , ""
+      , "newtype NonEmpty a = NonEmpty { unNonEmpty :: a }"
+      ]
+
+    expected = unlines
+      [ "module Some.Types where"
+      , ""
+      , "newtype NonEmpty a"
+      , "  = NonEmpty { unNonEmpty :: a }"
+      ]
+
+case34 :: Assertion
+case34 = expected @=? testStep (step indentIndentStyle { cVia = Indent 2 }) input
+  where
+    input = unlines
+      [ "module Some.Types where"
+      , ""
+      , "newtype NonEmpty a = NonEmpty { unNonEmpty :: a }"
+      , "     deriving (ToJSON, FromJSON) via Something Magic (NonEmpty a)"
+      ]
+
+    expected = unlines
+      [ "module Some.Types where"
+      , ""
+      , "newtype NonEmpty a"
+      , "  = NonEmpty { unNonEmpty :: a }"
+      , "  deriving (FromJSON, ToJSON)"
+      , "    via Something Magic (NonEmpty a)"
+      ]
+
+case35 :: Assertion
+case35 = expected @=? testStep (step indentIndentStyle { cBreakEnums = True, cBreakSingleConstructors = False }) input
+  where
+    input = unlines
+      [ "module Some.Types where"
+      , ""
+      , "data Foo = Foo"
+      , "  { _transfer :: MonetaryAmount"
+      , "      -> TransactionId"
+      , "      -> m (Either CreditTransferError TransactionId)"
+      , "  }"
+      ]
+
+    expected = unlines
+      [ "module Some.Types where"
+      , ""
+      , "data Foo = Foo"
+      , "  { _transfer :: MonetaryAmount -> TransactionId -> m (Either CreditTransferError TransactionId)"
+      , "  }"
+      ]
+
+case36 :: Assertion
+case36 = expected @=? testStep (step indentIndentStyle { cBreakEnums = True, cBreakSingleConstructors = False }) input
+  where
+    input = unlines
+      [ "module Some.Types where"
+      , ""
+      , "data Foo = Foo"
+      , "  { _transfer :: (a -> b)"
+      , "      -> TransactionId"
+      , "      -> m (Either CreditTransferError TransactionId)"
+      , "  }"
+      ]
+
+    expected = unlines
+      [ "module Some.Types where"
+      , ""
+      , "data Foo = Foo"
+      , "  { _transfer :: (a -> b) -> TransactionId -> m (Either CreditTransferError TransactionId)"
+      , "  }"
+      ]
+
+case37 :: Assertion
+case37 = expected @=? testStep (step indentIndentStyle { cVia = Indent 2 }) input
+  where
+    input = unlines
+      [ "module Some.Types where"
+      , ""
+      , "newtype UndoFlowData"
+      , "  = UndoFlowData { flowDataDetails :: FlowDataDetails }"
+      , "  deriving stock (Generic, Eq, Show)"
+      , "  deriving (ToJSON, FromJSON)"
+      , "    via AddConstTextFields '[\"type0\" := \"undo\","
+      , "                             \"type1\" := \"undo\","
+      , "                     \"reversal_indicator\" := \"Undo\"] FlowDataDetails"
+      ]
+
+    expected = unlines
+      [ "module Some.Types where"
+      , ""
+      , "newtype UndoFlowData"
+      , "  = UndoFlowData { flowDataDetails :: FlowDataDetails }"
+      , "  deriving stock (Eq, Generic, Show)"
+      , "  deriving (FromJSON, ToJSON)"
+      , "    via AddConstTextFields '[\"type0\" := \"undo\", \"type1\" := \"undo\", \"reversal_indicator\" := \"Undo\"] FlowDataDetails"
+      ]
+
+case38 :: Assertion
+case38 = expected @=? testStep (step indentIndentStyle { cVia = Indent 2 }) input
+  where
+    input = unlines
+      [ "data Flat = Flat"
+      , "  { foo :: Int"
+      , "  , bar :: Text"
+      , "  , baz :: Double"
+      , "  , qux :: Bool"
+      , "  }"
+      , "  deriving stock (Generic, Show, Eq)"
+      , "  deriving (FromJSON, ToJSON)"
+      , "    via GenericEncoded"
+      , "      '[ FieldLabelModifier :="
+      , "        '[ \"foo\" ==> \"nestFoo#foo\""
+      , "         , \"bar\" ==> \"nestBar#bar\""
+      , "         , \"baz\" ==> \"nestFoo#baz\""
+      , "         ]"
+      , "       ]"
+      , "      Flat"
+      ]
+
+    expected = unlines
+      [ "data Flat"
+      , "  = Flat"
+      , "      { foo :: Int"
+      , "      , bar :: Text"
+      , "      , baz :: Double"
+      , "      , qux :: Bool"
+      , "      }"
+      , "  deriving stock (Eq, Generic, Show)"
+      , "  deriving (FromJSON, ToJSON)"
+      , "    via GenericEncoded '[FieldLabelModifier := '[\"foo\" ==> \"nestFoo#foo\", \"bar\" ==> \"nestBar#bar\", \"baz\" ==> \"nestFoo#baz\"]] Flat"
+      ]
+
+case39 :: Assertion
+case39 = expected @=? testStep (step indentIndentStyle { cVia = Indent 2 }) input
+  where
+    input = unlines
+      [ "data CreditTransfer = CreditTransfer"
+      , "  { nestedCreditorInfo :: CreditorInfo"
+      , "  }"
+      , "  deriving stock (Show, Eq, Generic)"
+      , "  deriving (ToJSON, FromJSON) via"
+      , "    ( UntaggedEncoded NordeaCreditTransfer"
+      , "    & AddConstTextFields"
+      , "      '[ \"request_type\" ':= \"credit_transfer\""
+      , "       , \"provider\" ':= \"nordea\""
+      , "       ]"
+      , "    & FlattenFields '[\"nested_creditor_info\"]"
+      , "    & RenameKeys"
+      , "        '[ \"nested_creditor_info.creditor_agent_bic\" ==> \"creditor_agent_bic\""
+      , "         , \"nested_creditor_info.creditor_iban\" ==> \"creditor_iban\""
+      , "         , \"nested_creditor_info.creditor_name\" ==> \"creditor_name\""
+      , "         , \"nested_creditor_info.creditor_account\" ==> \"creditor_account\""
+      , "         ]"
+      , "    )"
+      ]
+
+    expected = unlines
+      [ "data CreditTransfer"
+      , "  = CreditTransfer"
+      , "      { nestedCreditorInfo :: CreditorInfo"
+      , "      }"
+      , "  deriving stock (Eq, Generic, Show)"
+      , "  deriving (FromJSON, ToJSON)"
+      , "    via (UntaggedEncoded NordeaCreditTransfer & AddConstTextFields '[\"request_type\" ':= \"credit_transfer\", \"provider\" ':= \"nordea\"] & FlattenFields '[\"nested_creditor_info\"] & RenameKeys '[\"nested_creditor_info.creditor_agent_bic\" ==> \"creditor_agent_bic\", \"nested_creditor_info.creditor_iban\" ==> \"creditor_iban\", \"nested_creditor_info.creditor_name\" ==> \"creditor_name\", \"nested_creditor_info.creditor_account\" ==> \"creditor_account\"])"
+      ]
+
+case40 :: Assertion
+case40 = expected @=? testStep (step indentIndentStyle { cBreakSingleConstructors = False }) input
+  where
+    input = unlines
+      [ "module X where"
+      , ""
+      , "data a :==> b    ="
+      , "                  Arr a b"
+      ]
+
+    expected = unlines
+      [ "module X where"
+      , ""
+      , "data a :==> b = Arr a b"
+      ]
+
+case41 :: Assertion
+case41 = expected @=? testStep (step indentIndentStyle) input
+  where
+    input = expected
+
+    expected = unlines
+      [ "module X where"
+      , ""
+      , "data Callback"
+      , "  -- | Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor"
+      , "  --   incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis"
+      , "  --   nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat."
+      , "  --   Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore"
+      , "  --   eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident,"
+      , "  --   sunt in culpa qui officia deserunt mollit anim id est laborum."
+      , "  = KafkaTopic"
+      , "      { callbackTopic :: CallbackTopic"
+      , "        -- ^ Name of topic to send updates to"
+      , "      , callbackFormat :: CallbackFormat"
+      , "        -- ^ The format used to send these updates"
+      , "      }"
+      , "  deriving stock (Eq, Generic, Show)"
+      , "  deriving (FromJSON, ToJSON) via IdiomaticWithDescription CallbackDesc Callback"
+      , "  deriving (HasGen) via Generically Callback"
+      , "  deriving (FromField) via JsonField Callback"
+      ]
+
+case42 :: Assertion
+case42 = expected @=? testStep (step indentIndentStyle) input
+  where
+    input = expected
+
+    expected = unlines
+      [ "module X where"
+      , ""
+      , "data SignupError"
+      , "  = IdempotencyConflict"
+      , "  | ValidationError Text -- TODO: might be a sumtype of possible error codes"
+      , "  deriving stock (Eq, Generic, Show)"
+      ]
+
+case43 :: Assertion
+case43 = expected @=? testStep (step indentIndentStyle { cBreakEnums = True, cBreakSingleConstructors = False }) input
+  where
+    input = expected
+
+    expected = unlines
+      [ "module X where"
+      , ""
+      , "data CallbackResult"
+      , "  -- | Callback successfully sent"
+      , "  = Success"
+      , "  -- | Kafka error received"
+      , "  | KafkaIssue KafkaError"
+      , "  deriving (Eq, Show)"
+      ]
+
+-- This test showcases a difficult to solve issue. If the comment is in a
+-- deriving clause, it's very hard to guess the correct position of the entire
+-- block. E.g. the deriving clause itself has the wrong position. However, if
+-- we look at all deriving clauses we know where they start and end.
+--
+-- This means that we've needed to make the decision to put all inline comments
+-- before the deriving clause itself
+case44 :: Assertion
+case44 = expected @=? testStep (step indentIndentStyle { cBreakEnums = True, cBreakSingleConstructors = False, cVia = Indent 2 }) input
+  where
+    input = unlines
+      [ "module X where"
+      , ""
+      , " data CreditTransfer = CreditTransfer"
+      , "   { amount :: Amount -- ^ 1 <= amount <= 999_999_999_999"
+      , "   , date :: Day"
+      , "   , accountNumber :: Account"
+      , "   }"
+      , "   deriving stock (Eq, Generic, Show)"
+      , "   deriving (FromJSON, ToJSON) via"
+      , "     AddConstTextFields"
+      , "       '[\"notification_type\" ':= \"credit_transaction\""
+      , "         -- Note that the bcio name has \"transaction\""
+      , "         -- rather than \"transfer\""
+      , "        ]"
+      , "        (UntaggedEncoded CreditTransfer)"
+      ]
+    expected = unlines
+      [ "module X where"
+      , ""
+      , "data CreditTransfer = CreditTransfer"
+      , "  { amount :: Amount"
+      , "    -- ^ 1 <= amount <= 999_999_999_999"
+      , "  , date :: Day"
+      , "  , accountNumber :: Account"
+      , "  }"
+      , "  -- Note that the bcio name has \"transaction\""
+      , "  -- rather than \"transfer\""
+      , "  deriving stock (Eq, Generic, Show)"
+      , "  deriving (FromJSON, ToJSON)"
+      , "    via AddConstTextFields '[\"notification_type\" ':= \"credit_transaction\"] (UntaggedEncoded CreditTransfer)"
+      ]
+
+case45 :: Assertion
+case45 = expected @=? testStep (step indentIndentStyle { cBreakEnums = True, cBreakSingleConstructors = False, cVia = Indent 2 }) input
+  where
+    input = expected
+    expected = unlines
+      [ "module X where"
+      , ""
+      , "data CreditTransfer = CreditTransfer"
+      , "  { amount :: Amount"
+      , "    -- ^ 1 <= amount <= 999_999_999_999"
+      , "  , date :: Day"
+      , "  , accountNumber :: Account"
+      , "  }"
+      , "  -- Note that the bcio name has \"transaction\""
+      , "  -- rather than \"transfer\""
+      , "  deriving stock (Eq, Generic, Show)"
+      , "  deriving (FromJSON, ToJSON)"
+      , "    via AddConstTextFields '[\"notification_type\" ':= \"credit_transaction\"] (UntaggedEncoded CreditTransfer)"
+      ]
+
+case46 :: Assertion
+case46 = expected @=? testStep (step indentIndentStyle { cBreakEnums = True, cBreakSingleConstructors = False, cVia = Indent 2 }) input
+  where
+    input = expected
+    expected = unlines
+      [ "module X where"
+      , ""
+      , "-- | A format detailing which encoding to use for the settlement events"
+      , "data CallbackFormat"
+      , "  -- | The Avro schema is to be used"
+      , "  = AvroEngineEvent"
+      , "  deriving (Bounded, Enum, Eq, Generic, Show)"
+      , "  deriving (FromJSON, ToJSON)"
+      , "    via TypeTaggedWithDescription FormatDesc CallbackFormat"
+      , "  deriving (HasGen)"
+      , "    via EnumBounded CallbackFormat"
+      ]
+
+case47 :: Assertion
+case47 = expected @=? testStep (step indentIndentStyle) input
+  where
+    input = expected
+    expected = unlines
+      [ "module X where"
+      , ""
+      , "-- | A GADT example"
+      , "data T a where"
+      , "  D1 :: Int -> T String"
+      , "  D2 :: T Bool"
+      , "  D3 :: (a, a) -> T [a]"
+      ]
+
+case48 :: Assertion
+case48 = expected @=? testStep (step indentIndentStyle) input
+  where
+    input = expected
+    expected = unlines
+      [ "module X where"
+      , ""
+      , "-- | A GADT example"
+      , "data T a where"
+      , "  D1 :: Int -> T String"
+      , "  D2 :: T Bool"
+      , "  D3 :: forall a. (Eq a, Bounded a) => (a, a) -> T [a]"
+      ]
+
+case49 :: Assertion
+case49 = expected @=? testStep (step indentIndentStyle) input
+  where
+    input = expected
+    expected = unlines
+      [ "module X where"
+      , ""
+      , "-- | A GADT example"
+      , "data T a where"
+      , "  D1 :: Int -> T String"
+      , "  D2 :: T Bool"
+      , "  D3 :: forall a. (Eq a) => (a, a) -> T [a]"
+      ]
+
+case50 :: Assertion
+case50 = expected @=? testStep (step indentIndentStyle { cCurriedContext = True }) input
+  where
+    input = expected
+    expected = unlines
+      [ "module X where"
+      , ""
+      , "-- | A GADT example"
+      , "data T a where"
+      , "  D1 :: Int -> T String"
+      , "  D2 :: T Bool"
+      , "  D3 :: forall a. Eq a => (a, a) -> T [a]"
+      ]
+
+case51 :: Assertion
+case51 = expected @=? testStep (step indentIndentStyle { cCurriedContext = True }) input
+  where
+    input = unlines
+      [ "module X where"
+      , ""
+      , "-- | A GADT example"
+      , "data T a where"
+      , "  D1 :: Int -> T String"
+      , "  D2 :: T Bool"
+      , "  D3 :: forall a. (Eq a) => (a, a) -> T [a]"
+      ]
+    expected = unlines
+      [ "module X where"
+      , ""
+      , "-- | A GADT example"
+      , "data T a where"
+      , "  D1 :: Int -> T String"
+      , "  D2 :: T Bool"
+      , "  D3 :: forall a. Eq a => (a, a) -> T [a]"
+      ]
+
+case52 :: Assertion
+case52 = expected @=? testStep (step indentIndentStyle { cBreakSingleConstructors = False, cCurriedContext = True }) input
+  where
+    input = unlines
+      [ "module X where"
+      , ""
+      , "data Foo = Foo"
+      , "  { foo :: forall a b. (Eq a, Bounded b) => a -> b -> [(a, b)]"
+      , "  }"
+      ]
+    expected = unlines
+      [ "module X where"
+      , ""
+      , "data Foo = Foo"
+      , "  { foo :: forall a b. Eq a => Bounded b => a -> b -> [(a, b)]"
+      , "  }"
+      ]
+
+case53 :: Assertion
+case53 = expected @=? testStep (step indentIndentStyle { cMaxColumns = MaxColumns 80 }) input
+  where
+    input = unlines
+      [ "newtype Foo m a"
+      , "  = Foo (m a)"
+      , "  deriving newtype (Functor, Applicative, Monad, MonadError, MonadCatch, Foldable, Monoid)"
+      ]
+    expected = unlines
+      [ "newtype Foo m a"
+      , "  = Foo (m a)"
+      , "  deriving newtype"
+      , "    ( Applicative"
+      , "    , Foldable"
+      , "    , Functor"
+      , "    , Monad"
+      , "    , MonadCatch"
+      , "    , MonadError"
+      , "    , Monoid"
+      , "    )"
+      ]
+
+case54 :: Assertion
+case54 = expected @=? testStep (step indentIndentStyle { cMaxColumns = MaxColumns 80 }) input
+  where
+    input = unlines
+      [ "newtype Foo m a"
+      , "  = Foo (m a)"
+      , "  deriving newtype (Functor, Applicative, Monad)"
+      ]
+    expected = unlines
+      [ "newtype Foo m a"
+      , "  = Foo (m a)"
+      , "  deriving newtype (Applicative, Functor, Monad)"
+      ]
+
 sameSameStyle :: Config
-sameSameStyle = Config SameLine SameLine 2 2
+sameSameStyle = Config SameLine SameLine 2 2 False True SameLine False NoMaxColumns
 
 sameIndentStyle :: Config
-sameIndentStyle = Config SameLine (Indent 2) 2 2
+sameIndentStyle = Config SameLine (Indent 2) 2 2 False True SameLine False NoMaxColumns
 
 indentSameStyle :: Config
-indentSameStyle = Config (Indent 2) SameLine 2 2
+indentSameStyle = Config (Indent 2) SameLine 2 2 False True SameLine False NoMaxColumns
 
 indentIndentStyle :: Config
-indentIndentStyle = Config (Indent 2) (Indent 2) 2 2
+indentIndentStyle = Config (Indent 2) (Indent 2) 2 2 False True SameLine False NoMaxColumns
 
 indentIndentStyle4 :: Config
-indentIndentStyle4 = Config (Indent 4) (Indent 4) 4 4
+indentIndentStyle4 = Config (Indent 4) (Indent 4) 4 4 False True SameLine False NoMaxColumns