Data.Text.Display.Generic

Generic machinery for automatically deriving display instances for record types

Documentation

class GDisplay1 f where

Generic typeclass machinery for inducting on the structure of the type, such that we can thread Display instances through the structure of the type. The primary use case is for implementing RecordInstance, which does this "threading" for record fields. This machinery does, crucially, depend on child types (i.e. the type of a record field) having a Display instance.

Since: 0.0.5.0

Methods

gdisplayBuilder1 :: f p -> Builder

Instances

GDisplay1 (U1 :: Type -> Type)

Defined in Data.Text.Display.Generic

Methods

gdisplayBuilder1 :: U1 p -> Builder

GDisplay1 (V1 :: Type -> Type)

Defined in Data.Text.Display.Generic

Methods

gdisplayBuilder1 :: V1 p -> Builder

(GDisplay1 a, GDisplay1 b) => GDisplay1 (a :*: b)

Defined in Data.Text.Display.Generic

Methods

gdisplayBuilder1 :: (a :*: b) p -> Builder

(GDisplay1 a, GDisplay1 b) => GDisplay1 (a :+: b)

Defined in Data.Text.Display.Generic

Methods

gdisplayBuilder1 :: (a :+: b) p -> Builder

Display c => GDisplay1 (K1 i c :: Type -> Type)

This is the most important instance, it can be considered as the "base case". It requires a non-generic Display instance. All this generic machinery can be conceptualized as distributing these displayBuilder calls across a product type.

Defined in Data.Text.Display.Generic

Methods

gdisplayBuilder1 :: K1 i c p -> Builder

(Constructor c, GDisplay1 f) => GDisplay1 (M1 C c f)

Defined in Data.Text.Display.Generic

Methods

gdisplayBuilder1 :: M1 C c f p -> Builder

GDisplay1 f => GDisplay1 (M1 D s f)

Defined in Data.Text.Display.Generic

Methods

gdisplayBuilder1 :: M1 D s f p -> Builder

(Selector s, GDisplay1 f) => GDisplay1 (M1 S s f)

Defined in Data.Text.Display.Generic

Methods

gdisplayBuilder1 :: M1 S s f p -> Builder

gdisplayBuilderDefault :: (Generic a, GDisplay1 (Rep a)) => a -> Builder

newtype RecordInstance a

This wrapper allows you to create an Display instance for a record, so long as all the record fields have a Display instance as well.

Example

data Password = Password
 deriving Display
   via (OpaqueInstance "[REDACTED]" Password)

data MyRecord =
   MyRecord
     { fieldA :: String
     , fieldB :: Maybe String
     , fieldC :: Int
     , pword :: Password
     }
     deriving stock (Generic)
     deriving (Display) via (RecordInstance MyRecord)

putStrLn . Data.Text.unpack . display $ MyRecord "hello" (Just "world") 22 Password

MyRecord
  { fieldA = hello
  , fieldB = Just world
  , fieldC = 22
  , pword = [REDACTED]
  }

Since: 0.0.5.0

Constructors

RecordInstance

Fields

• unDisplayProduct :: a

Instances

Generic a => Generic (RecordInstance a)

Defined in Data.Text.Display.Generic

Associated Types

type Rep (RecordInstance a) :: Type -> Type

Methods

from :: RecordInstance a -> Rep (RecordInstance a) x

to :: Rep (RecordInstance a) x -> RecordInstance a

(AssertNoSumRecordInstance Display a, Generic a, GDisplay1 (Rep a)) => Display (RecordInstance a)

We leverage the AssertNoSum type family to prevent consumers from deriving instances for sum types. Sum types should use a manual instance or derive one via ShowInstance.

Since: 0.0.5.0

Defined in Data.Text.Display.Generic

Methods

displayBuilder :: RecordInstance a -> Builder

displayList :: [RecordInstance a] -> Builder

displayPrec :: Int -> RecordInstance a -> Builder

type Rep (RecordInstance a)

Defined in Data.Text.Display.Generic

type Rep (RecordInstance a) = Rep a

type family HasSum f where ...

This type family is lifted from generic-data. We use it to prevent the user from deriving a RecordInstance for sum types

Since: 0.0.5.0

Equations

HasSum V1 = 'False

HasSum U1 = 'False

HasSum (K1 i c) = 'False

HasSum (M1 i c f) = HasSum f

HasSum (f :*: g) = HasSum f || HasSum g

HasSum (f :+: g) = 'True

class Assert (pred :: Bool) (msg :: ErrorMessage)

Instances

(TypeError msg :: ()) ~ '() => Assert 'False msg

Defined in Data.Text.Display.Generic

Assert 'True msg

Defined in Data.Text.Display.Generic

type AssertNoSumRecordInstance (constraint :: Type -> Constraint) a = Assert (Not (HasSum (Rep a))) ((((('Text "\128683 Cannot derive " ':<>: 'ShowType constraint) ':<>: 'Text " instance for ") ':<>: 'ShowType a) ':<>: 'Text " via RecordInstance due to sum type") ':$$: 'Text "\128161 Sum types should use a manual instance or derive one via ShowInstance.")

Constraint to prevent misuse of RecordInstance deriving via mechanism.

Example

data MySum = A | B | C deriving stock (Generic) deriving (Display) via (RecordInstance MySum)

   • 🚫 Cannot derive Display instance for MySum via RecordInstance due to sum type
     💡 Sum types should use a manual instance or derive one via ShowInstance.
   • When deriving the instance for (Display MySum)

Since: 0.0.5.0