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arch:Type
Archetype is another attempt at IDL (interface description/definition language) inspired by Dhall configuration language.
TODO
TODO
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Protocol/interface is described using types. RPC/REST calls are just types too.
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Has a notion of primitive types that code generator has to understand. It allows us to define:
prim type gRPC : forall(request : Type) -> forall(response : Type) -> gRPC request responseSame using Unicode syntax:
prim type gRPC : ∀(request : Type) → ∀(response : Type) → gRPC request responseIf the code generator doesn't understand gRPC then it will fail.
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Syntax is an extension of Dhall language. Dhall is also used to encode Archetype intermediate representation consumed by code generator.
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Code generators are explicit; there is no default code generator. This is to prevent implementation to be tied to a specific representation too much, and it also encourages users to think of code generators as something they can provide them selves.
As a consequence service API is defined by interface description in the form of Archetype IDL file, and suitable code generator(s).
-- Primitive types are those that are already known to the code generator.
-- It's just a way how to explicitly surface them in Archetype.
prim type NonEmpty : forall(a : Type) -> NonEmpty a
prim type UUID : Type
-- REST and RPC calls are modeled as primitive types as well. This allows us
-- to support any transport layer supported by individual code generator.
prim type RpcCall :
forall(request : Type)
-> forall(response : Type)
-> RpcCall request response
-- Normal types are those for which code will be generated.
type UserId = UUID
-- Enums are supported as a special case of sum types.
type UserRole = < Admin | NormalUser >
-- A user, what a surprise.
type User =
{ id : UserId
, full-name : Text
, emails : NonEmpty Text
, verified : Bool
, role : UserRole
}
type GetUserError =
< NoSuchUser
| AccountDisabled
| OtherError : Text
>
prim type Response :
forall(error : Type)
-> forall(r : Type)
-> Response error r
type rpc-get-user = RpcCall UserId (Response GetUserError User)
ark codegen --backend=EXECUTABLE [--backend-argument=ARGUMENT ...] [FILE]
ark lint [FILE]
ark diff FILE FILE
ark help
ark version
ark {--help|-h}
ark {--version|-V}
In principle Archetype compiler ark does this:
┌────────────────────┐
┌─────────┐ ┌────────────────────┐│
Interface │ │ Dhall │ ││ Native
description ───>│ ark │─────────────>│ code generator ││─────> code
(Archetype) │ │ via pipe │ │┘ (.hs, .psc, etc.)
└─────────┘ └────────────────────┘
However, the implementation of code generator should behave as a pure function, or at least as much as one can be approximated. This allows us to safely examine the output of code generator.
Archetype
│
│
┌──────────│──────────┐
│ ark ▼ │
│ ┌─────────────┐ │
│ │ │ │
│ │ front │ │
│ │ end │ │
│ │ │ │
│ └─────────────┘ │
│ │ │
│ IR │ │
│ ▼ │
│ ┌─────────────┐ │ IR (Dhall) ┌─────────────┐
│ │ │───────────────────>│ │
│ │ back end │ │ │ code │
│ │ executor │ │ Files (Dhall) │ generator │
│ │ │<───────────────────│ │
│ └─────────────┘ │ └─────────────┘
│ │ │
└──────────│──────────┘
│
▼
Generated
Files
┌───────────┐
│ Archetype │
│ source │
│ code │
└───────────┘
│
Parse │
▼
┌───────────┐
│ Archetype │
│ │
│ AST │
└───────────┘
│
Embed │ ┌───────┐
▼ │ │
┌───────────┐ │ Type check and normalise
│ Dhall │ │
│ │<────┘
│ AST │
└───────────┘
│
Simplify │
▼
┌───────────┐
│ │
│ IR │
│ │
└───────────┘
│
Serialise │
▼
┌───────────┐
│ │
│ Dhall │
│ │
└───────────┘
│
Send │
▼
┌───────────┐
│ Code │
│ │
│ Generator │
└───────────┘
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