Refractive PPX

PPX Rewriter for generating Refractive lenses and selectors.

To enable

Install @tizoc/refractive_ppx:

npm i --save-dev @tizoc/refractive_ppx

Add this to your bsconfig.json file:

  "ppx-flags": [
    "@tizoc/refractive_ppx/ppx.exe"
  ],

How to use

Add a [@refractive.derive] annotation to a type declaration (only record types are supported):

[@refractive.derive]
type t = { ... };

The expansion will define two new modules:

• Lenses if the type name is t, or <Titlecased-type-name>Lenses for any other name.
• Selectors if the type name is t, or <Titlecased-type-name>Selectors for any other name.

The Lenses module will include one lense declaration for each record field, with the same name. The Selectors module will include one selector declaration for each record field, with the same name. The path will be the same as the name of the field, and a lense of the same name will be used.

For recursive type definitions, the [@refractive.derive] has to be added to each type declaration for which lenses and selectors should be generated.

Example

The following declaration:

module User = {
  [@refractive.derive]
  type t = {
    id:       string,
    email:    string,
    username: string,
    score:    int,
  };
};

gets expanded to:

module User = {
  type t = {
    id:       string,
    email:    string,
    username: string,
    score:    int,
  };

  module Lenses = {
    let id =
      Refractive.Lens.make(
        ~get=x => x.id,
        ~set=(newVal, x) => {...x, id: newVal},
      );
    let email =
      Refractive.Lens.make(
        ~get=x => x.email,
        ~set=(newVal, x) => {...x, email: newVal},
      );
    let username =
      Refractive.Lens.make(
        ~get=x => x.username,
        ~set=(newVal, x) => {...x, username: newVal},
      );
    let score =
      Refractive.Lens.make(
        ~get=x => x.score,
        ~set=(newVal, x) => {...x, score: newVal},
      );
  };

  module Selectors = {
    let id       = Refractive.Selector.make(~lens=Lenses.id,       ~path=[|"id"|]);
    let email    = Refractive.Selector.make(~lens=Lenses.email,    ~path=[|"email"|]);
    let username = Refractive.Selector.make(~lens=Lenses.username, ~path=[|"username"|]);
    let score    = Refractive.Selector.make(~lens=Lenses.score,    ~path=[|"score"|]);
  };
};

For a type named t, no prefix is added to the generated modules. Otherwise, the name of the type is titlecased and used as a prefix. A type named user will generate modules named UserLenses and UserSelectors.