package ocaml-migrate-parsetree

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Convert OCaml parsetrees between different versions

Install 

dune-project
 Dependency

github.com Readme Changelog LGPL-2.1-only WITH OCaml-LGPL-linking-exception License Edit opam file Versions (16)

Authors

  1. F
    Frédéric Bour <frederic.bour@lakaban.net>
  2. J
    Jérémie Dimino <jeremie@dimino.org>

Maintainers

  1. F
    frederic.bour@lakaban.net

Sources

ocaml-migrate-parsetree-v1.7.1.tbz
sha256=41a37f1ad93ffa1e40e5c91002e6840cf9b6c37385da1c9db833014e8d6103b8
sha512=05998114f8caeb0dc1af8bc2b76f80a2b4cba25597088fff01a6643d40c3a49e55b1e2f369fe8959a72c79417ac1438ab06db7bb8cd377a55612b4ab68083576

doc/ocaml-migrate-parsetree/Migrate_parsetree/Ast_405/Ast_mapper/index.html

Module Ast_405.Ast_mapper

The interface of a -ppx rewriter

A -ppx rewriter is a program that accepts a serialized abstract syntax tree and outputs another, possibly modified, abstract syntax tree. This module encapsulates the interface between the compiler and the -ppx rewriters, handling such details as the serialization format, forwarding of command-line flags, and storing state.

mapper allows to implement AST rewriting using open recursion. A typical mapper would be based on default_mapper, a deep identity mapper, and will fall back on it for handling the syntax it does not modify. For example:

open Asttypes
open Parsetree
open Ast_mapper

let test_mapper argv =
  { default_mapper with
    expr = fun mapper expr ->
      match expr with
      | { pexp_desc = Pexp_extension ({ txt = "test" }, PStr [])} ->
        Ast_helper.Exp.constant (Const_int 42)
      | other -> default_mapper.expr mapper other; }

let () =
  register "ppx_test" test_mapper

This -ppx rewriter, which replaces [%test] in expressions with the constant 42, can be compiled using ocamlc -o ppx_test -I +compiler-libs ocamlcommon.cma ppx_test.ml.

A generic Parsetree mapper

type mapper = {
  1. attribute : mapper -> Parsetree.attribute -> Parsetree.attribute;
  2. attributes : mapper -> Parsetree.attribute list -> Parsetree.attribute list;
  3. case : mapper -> Parsetree.case -> Parsetree.case;
  4. cases : mapper -> Parsetree.case list -> Parsetree.case list;
  5. class_declaration : mapper -> Parsetree.class_declaration -> Parsetree.class_declaration;
  6. class_description : mapper -> Parsetree.class_description -> Parsetree.class_description;
  7. class_expr : mapper -> Parsetree.class_expr -> Parsetree.class_expr;
  8. class_field : mapper -> Parsetree.class_field -> Parsetree.class_field;
  9. class_signature : mapper -> Parsetree.class_signature -> Parsetree.class_signature;
  10. class_structure : mapper -> Parsetree.class_structure -> Parsetree.class_structure;
  11. class_type : mapper -> Parsetree.class_type -> Parsetree.class_type;
  12. class_type_declaration : mapper -> Parsetree.class_type_declaration -> Parsetree.class_type_declaration;
  13. class_type_field : mapper -> Parsetree.class_type_field -> Parsetree.class_type_field;
  14. constructor_declaration : mapper -> Parsetree.constructor_declaration -> Parsetree.constructor_declaration;
  15. expr : mapper -> Parsetree.expression -> Parsetree.expression;
  16. extension : mapper -> Parsetree.extension -> Parsetree.extension;
  17. extension_constructor : mapper -> Parsetree.extension_constructor -> Parsetree.extension_constructor;
  18. include_declaration : mapper -> Parsetree.include_declaration -> Parsetree.include_declaration;
  19. include_description : mapper -> Parsetree.include_description -> Parsetree.include_description;
  20. label_declaration : mapper -> Parsetree.label_declaration -> Parsetree.label_declaration;
  21. location : mapper -> Location.t -> Location.t;
  22. module_binding : mapper -> Parsetree.module_binding -> Parsetree.module_binding;
  23. module_declaration : mapper -> Parsetree.module_declaration -> Parsetree.module_declaration;
  24. module_expr : mapper -> Parsetree.module_expr -> Parsetree.module_expr;
  25. module_type : mapper -> Parsetree.module_type -> Parsetree.module_type;
  26. module_type_declaration : mapper -> Parsetree.module_type_declaration -> Parsetree.module_type_declaration;
  27. open_description : mapper -> Parsetree.open_description -> Parsetree.open_description;
  28. pat : mapper -> Parsetree.pattern -> Parsetree.pattern;
  29. payload : mapper -> Parsetree.payload -> Parsetree.payload;
  30. signature : mapper -> Parsetree.signature -> Parsetree.signature;
  31. signature_item : mapper -> Parsetree.signature_item -> Parsetree.signature_item;
  32. structure : mapper -> Parsetree.structure -> Parsetree.structure;
  33. structure_item : mapper -> Parsetree.structure_item -> Parsetree.structure_item;
  34. typ : mapper -> Parsetree.core_type -> Parsetree.core_type;
  35. type_declaration : mapper -> Parsetree.type_declaration -> Parsetree.type_declaration;
  36. type_extension : mapper -> Parsetree.type_extension -> Parsetree.type_extension;
  37. type_kind : mapper -> Parsetree.type_kind -> Parsetree.type_kind;
  38. value_binding : mapper -> Parsetree.value_binding -> Parsetree.value_binding;
  39. value_description : mapper -> Parsetree.value_description -> Parsetree.value_description;
  40. with_constraint : mapper -> Parsetree.with_constraint -> Parsetree.with_constraint;
}

A mapper record implements one "method" per syntactic category, using an open recursion style: each method takes as its first argument the mapper to be applied to children in the syntax tree.

val default_mapper : mapper

A default mapper, which implements a "deep identity" mapping.

Convenience functions to write mappers

val map_opt : ('a -> 'b) -> 'a option -> 'b option
val extension_of_error : Location.error -> Parsetree.extension

Encode an error into an 'ocaml.error' extension node which can be inserted in a generated Parsetree. The compiler will be responsible for reporting the error.

val attribute_of_warning : Location.t -> string -> Parsetree.attribute

Encode a warning message into an 'ocaml.ppwarning' attribute which can be inserted in a generated Parsetree. The compiler will be responsible for reporting the warning.

type nonrec location_error = Location.error
val error_of_exn : exn -> location_error option
val register_error_of_exn : (exn -> location_error option) -> unit
val report_exception : Format.formatter -> exn -> unit
val get_error_message : location_error -> string
val set_error_message : location_error -> string -> location_error
val make_error_of_message : loc:Location.t -> string -> sub:(Location.t * string) list -> location_error
val print_error : Format.formatter -> location_error -> unit
val raise_error : location_error -> 'a