add -as-pp flag

Author: bobzhang

jscomp/common/js_config.ml

@@ -92,4 +92,6 @@ let as_ppx = ref false
 
 let mono_empty_array = ref true
 
-let customize_runtime = ref None 
+let customize_runtime = ref None 
+
+let as_pp = ref false

jscomp/common/js_config.mli

@@ -100,4 +100,5 @@ val no_export: bool ref
 val as_ppx : bool ref 
 
 val mono_empty_array : bool ref
-val customize_runtime : string option ref 
+val customize_runtime : string option ref 
+val as_pp: bool ref

jscomp/core/js_implementation.ml

@@ -67,7 +67,12 @@ let after_parsing_sig ppf  outputprefix ast  =
         ast 
 
     end;
-  if !Js_config.syntax_only then 
+  if !Js_config.as_pp then begin 
+      output_string stdout Config.ast_intf_magic_number;
+      output_value stdout (!Location.input_name : string);
+      output_value stdout ast;
+  end; 
+  if !Js_config.syntax_only then
     Warnings.check_fatal()
   else 
     begin 
@@ -170,6 +175,11 @@ let after_parsing_impl ppf  outputprefix (ast : Parsetree.structure) =
       Ml ~output:(outputprefix ^ Literals.suffix_ast)
       ast
   end ;
+  if !Js_config.as_pp then begin 
+    output_string stdout Config.ast_impl_magic_number;
+    output_value stdout (!Location.input_name : string);
+    output_value stdout ast;
+  end; 
   if !Js_config.syntax_only then 
     Warnings.check_fatal ()
   else 

jscomp/main/js_main.ml

@@ -287,7 +287,8 @@ let buckle_script_flags : (string * Bsc_args.spec * string) array =
 
     "-as-ppx", set Js_config.as_ppx, 
     "*internal*As ppx for editor integration";
-
+    "-as-pp", unit_call(fun _ ->  Js_config.as_pp := true ; Js_config.syntax_only := true),
+    "*internal*As pp to interact with native tools";
     "-no-alias-deps", set Clflags.transparent_modules, 
     "*internal*Do not record dependencies for module aliases";
 

jscomp/test/hello_res.res

@@ -0,0 +1,4 @@
+
+let b = List.length(list{1,2,3})
+let a = b - 1
+Js.log ("hello, res")

jscomp/test/hello_res.resi

@@ -0,0 +1 @@
+let a : int