[@@deriving show]: add with_path option, to skip module path.

README.md

@@ -153,6 +153,24 @@ It is also possible to use `[@polyprinter]`. The difference is that for a type `
 
 The function `fprintf` is locally defined in the printer.
 
+By default all constructors are printed with prefix which is dot-separated filename and module path. For example
+``` ocaml
+# module X = struct type t = C [@@deriving show] end;;
+...
+# X.(show C);;
+- : Ppx_deriving_runtime.string = "X.C"
+```
+
+This code will create printers which return the string `X.C`, `X` is a module path and `C` is a constructor name. File's name is omitted in the toplevel. To skip all module paths the one needs to derive show with option `with_path` (which defaults to `true`)
+
+``` ocaml
+# module X = struct type t = C [@@deriving show { with_path = false }] end;;
+...
+# X.(show C);;
+- : Ppx_deriving_runtime.string = "C"
+```
+
+
 Plugins: eq and ord
 -------------------
 

src_plugins/ppx_deriving_show.cppo.ml

@@ -12,10 +12,15 @@ open Ast_convenience
 let deriver = "show"
 let raise_errorf = Ppx_deriving.raise_errorf
 
+type options = { with_path : bool }
+
 let parse_options options =
+  let with_path = ref true in
   options |> List.iter (fun (name, expr) ->
     match name with
-    | _ -> raise_errorf ~loc:expr.pexp_loc "%s does not support option %s" deriver name)
+    | "with_path" -> with_path := Ppx_deriving.Arg.(get_expr ~deriver bool) expr
+    | _ -> raise_errorf ~loc:expr.pexp_loc "%s does not support option %s" deriver name);
+  { with_path = !with_path }
 
 let attr_nobuiltin attrs =
   Ppx_deriving.(attrs |> attr ~deriver "nobuiltin" |> Arg.get_flag ~deriver)
@@ -42,23 +47,23 @@ let wrap_printer quoter printer =
     [%expr (let fprintf = Format.fprintf in [%e printer]) [@ocaml.warning "-26"]]
 
 let pp_type_of_decl ~options ~path type_decl =
-  parse_options options;
+  let _ = parse_options options in
   let typ = Ppx_deriving.core_type_of_type_decl type_decl in
   Ppx_deriving.poly_arrow_of_type_decl
     (fun var -> [%type: Format.formatter -> [%t var] -> Ppx_deriving_runtime.unit])
     type_decl
     [%type: Format.formatter -> [%t typ] -> Ppx_deriving_runtime.unit]
 
 let show_type_of_decl ~options ~path type_decl =
-  parse_options options;
+  let _ = parse_options options in
   let typ = Ppx_deriving.core_type_of_type_decl type_decl in
   Ppx_deriving.poly_arrow_of_type_decl
     (fun var -> [%type: Format.formatter -> [%t var] -> Ppx_deriving_runtime.unit])
     type_decl
     [%type: [%t typ] -> Ppx_deriving_runtime.string]
 
 let sig_of_type ~options ~path type_decl =
-  parse_options options;
+  let _ = parse_options options in
   [Sig.value (Val.mk (mknoloc (Ppx_deriving.mangle_type_decl (`Prefix "pp") type_decl))
               (pp_type_of_decl ~options ~path type_decl));
    Sig.value (Val.mk (mknoloc (Ppx_deriving.mangle_type_decl (`Prefix "show") type_decl))
@@ -182,7 +187,7 @@ let rec expr_of_typ quoter typ =
                    deriver (Ppx_deriving.string_of_core_type typ)
 
 let str_of_type ~options ~path ({ ptype_loc = loc } as type_decl) =
-  parse_options options;
+  let show_opts = parse_options options in
   let quoter = Ppx_deriving.create_quoter () in
   let path = Ppx_deriving.path_of_type_decl ~path type_decl in
   let prettyprinter =
@@ -192,7 +197,11 @@ let str_of_type ~options ~path ({ ptype_loc = loc } as type_decl) =
     | Ptype_variant constrs, _ ->
       let cases =
         constrs |> List.map (fun { pcd_name = { txt = name' }; pcd_args; pcd_attributes } ->
-          let constr_name = Ppx_deriving.expand_path ~path name' in
+          let constr_name =
+            let path = if show_opts.with_path then path else [] in
+            Ppx_deriving.expand_path ~path name'
+          in
+
           match attr_printer pcd_attributes, pcd_args with
           | Some printer, Pcstr_tuple(args) ->
             let rec range from_idx to_idx =

src_test/test_deriving_show.cppo.ml

@@ -214,6 +214,17 @@ let test_variant_printer ctxt =
   assert_equal ~printer
     "fourth: 8 4" (show_variant_printer (Fourth(8,4)))
 
+type no_full    = NoFull   of int [@@deriving show { with_path = false }]
+type with_full  = WithFull of int [@@deriving show { with_path = true  }]
+module WithFull = struct
+  type t = A of int [@@deriving show ]
+end
+let test_paths_printer ctxt =
+  assert_equal ~printer "(NoFull 1)"   (show_no_full   (NoFull 1));
+  assert_equal ~printer "(Test_deriving_show.WithFull 1)" (show_with_full (WithFull 1));
+  assert_equal ~printer "(Test_deriving_show.WithFull.A 1)" (WithFull.show (WithFull.A 1));
+  ()
+
 let suite = "Test deriving(show)" >::: [
     "test_alias"           >:: test_alias;
     "test_variant"         >:: test_variant;
@@ -232,5 +243,6 @@ let suite = "Test deriving(show)" >::: [
     "test_std_shadowing"   >:: test_std_shadowing;
     "test_poly_app"        >:: test_poly_app;
     "test_variant_printer" >:: test_variant_printer;
+    "test_paths"           >:: test_paths_printer;
     "test_result"          >:: test_result
   ]