ppx_deriving_typename

This project serves as a simple example of how to build type driver ppx rewriters. It defines a silly ppx ppx_deriving_typename for deriving the names of custom data types defined with a [@@deriving typename] attribute.

For example:

type address = Email of string [@@deriving typename]

type person = { name : string } [@@deriving typename]

yields the following code once piped through the ppx processor:

type address = | Email of string 
let _ = fun (_ : address)  -> () 
let (address_name : string) = "address" 
let _ = address_name 
type person = { name: string }
let _ = fun (_ : person)  -> () 
let (person_name : string) = "person" 
let _ = person_name 

The rewriter itself is defined in ppx/ppx_deriving_typename.ml.

Build and run

make test to execute the code in test/run.ml. make test-source to print the rewritten source of test/run.ml.

How it works

The ppx driver is defined in ppx/ppx_derive_typename.ml. The implementation uses the following libraries and other ppx rewriters:

• Ppx_core - Standard library for ppx rewriters
• Ppx_type_conv - A support library for type driven code generators
• Ppx_driver - Driver for AST transformers
• Ppx_metaquot - A ppx rewriter allowing you to write values representing the OCaml AST in the OCaml syntax.