purescript-tscompat

This library aims to provide types and type classes for typechecking interop with Typescript code without the need for conversion.

In conjuction with purescript-readts, purescript bindings for JS libraries which are written in Typescript or have type definitions can be created with little effort.

Types and Typeclasses

IsTSEq a b - Given a standard purescript type a does it match b where b can contain the following types:

Type	TS type	Matches
Any	any	Anything
OneOf (typed :: A, typed :: B, typed :: C)	(A|B|C)	Either one of A,B or C
StringConst "text"	"text"	An exact string
OptionRecord (optional :: A, mandatory :: B) (mandatory :: B)	{optional? : A; mandatory: B }	A record which optionally contains fields from the first row but must contain all the fields specified in the second. All fields are checked with IsTSEq.

In addition to these equivalences the following additional rules apply:

Int will match Number

Effect b matches EffectFn1 a b - very useful for event handlers when you don't need the event.

Nullable a matches a if it's one of the optional properties in OptionRecord.

Examples

Given the following definitions:

type DialogPropsO r = (
  key :: OneOf (
    typed :: String,
    typed :: Number),
  fullScreen :: Boolean,
  fullWidth :: Boolean,
  scroll :: OneOf (
    typed :: StringConst "paper",
    typed :: StringConst "body")
  | r)

type DialogPropsM = (open :: Boolean)
type DialogProps = DialogPropsO DialogPropsM

paper :: StringConst "paper"
paper = unsafeCoerce "paper"

body :: StringConst "body"
body = unsafeCoerce "body"

dialog :: forall a. IsTSEq (Record a) (OptionRecord DialogProps DialogPropsM) => Record a -> Unit

Usage:

dialog {key: 1}
-- Fails because `open` is not specified
dialog {open: true, scroll: body} 
-- Succeeds 
dialog {open: false, key: "stringKey", fullWidth: toNullable $ Just true}
-- Succeeds because optional fields can be Nullable