Add mustache templates.

.merlin

@@ -2,6 +2,7 @@ S lib
 S syntax
 S tools
 S ppx
+S mustache
 
 B _build/*
 

_oasis

@@ -26,6 +26,10 @@ Flag ppx
   Description: Build the ppx syntax extension.
   Default: true
 
+Flag mustache
+  Description: Build the mustache syntax extension.
+  Default: true
+
 Library tyxml
   FindlibName: tyxml
   Path: implem
@@ -160,6 +164,36 @@ Executable ppx_reflect
   BuildDepends: ppx_tools.metaquot, tyxml.tools
   CompiledObject: best
 
+## Template
+
+Library ppx_mustache
+  Build$: flag(ppx) && flag(mustache)
+  Install$: flag(ppx) && flag(mustache)
+  FindlibName: mustache
+  FindlibParent: ppx
+  InternalModules: Ppx_tyxml_empty
+  Path: ppx
+  XMETADescription:
+    Well typed templates for HTML and SVG (ppx)
+  XMETARequires: tyxml
+  XMETAExtraLines: ppx = "ppx_tyxml_mustache"
+
+Executable ppx_tyxml_mustache
+  Build$: flag(ppx) && flag(mustache)
+  Install$: flag(ppx) && flag(mustache)
+  Path: mustache
+  MainIs: ppx_tyxml_mustache.ml
+  BuildDepends: tyxml.ppx.internal, mustache
+  CompiledObject: best
+
+Executable tymustache
+  Build$: flag(ppx) && flag(mustache)
+  Install$: flag(ppx) && flag(mustache)
+  Path: mustache
+  MainIs: tymustache.ml
+  BuildDepends: tyxml.ppx.internal, mustache
+  CompiledObject: best
+
 ## Tests
 
 Executable emit_big

mustache/.merlin

@@ -0,0 +1,2 @@
+PKG mustache
+REC

mustache/ppx_tyxml_mustache.ml

@@ -0,0 +1,211 @@
+
+open Ast_helper
+module AC = Ast_convenience
+
+let mustache_from_file file =
+  let chan = open_in file in
+  let lex = Lexing.from_channel chan in
+  Location.init lex file ;
+  let t = Mustache.parse_lx lex in
+  close_in chan ;
+  t
+
+let mustache_from_string ~loc string =
+  let lex = Lexing.from_string string in
+  lex.Lexing.lex_curr_p <- loc ;
+  Mustache.parse_lx lex
+
+let antiquot_pcdata ~loc ~lang var =
+  let pcdata = Ppx_common.make ~loc lang "pcdata" in
+  AC.list [
+    Exp.apply ~loc pcdata
+      [Ppx_common.Label.nolabel, AC.evar var]
+  ]
+
+module Var = struct
+
+  module Env = Map.Make(String)
+
+  type kind =
+    | Var
+    | Expr
+    | Section of kind Env.t
+
+  let pp fmt = function
+    | Var -> Format.pp_print_string fmt "variable"
+    | Expr -> Format.pp_print_string fmt "unescaped variable"
+    | Section _ -> Format.pp_print_string fmt "section"
+
+  let rec equal k k' = match k, k' with
+    | Var, Var | Expr, Expr -> true
+    | Section env, Section env' ->
+      Env.equal equal env env'
+    | _, _ -> false
+
+  let error s k k' =
+    Location.error @@ Format.asprintf
+      "Variable %s is used both as a %a and a %a. This is not allowed."
+      s   pp k'   pp k
+
+  let add env s k =
+    if Env.mem s env then
+      let k' = Env.find s env in
+      if equal k k then env
+      else raise @@ Location.Error (error s k k')
+    else
+      Env.add s k env
+
+  let union =
+    let f s parentkind kind = match parentkind, kind with
+      | Some k, Some k' -> raise @@ Location.Error (error s k k')
+      | Some k, None | None, Some k -> Some k
+      | None, None -> None
+    in Env.merge f
+
+  let section env s secenv =
+    let k = Section secenv in
+    add env s k
+
+end
+
+module Template = struct
+
+  type t = desc list
+  and desc =
+    | Markup of string
+    | Pcdata of string
+    | Expr of string
+    | Section of section
+  and section = {
+    inverted : bool;
+    name: string;
+    contents: t;
+  }
+
+  let rec of_mustache resolve =
+    Mustache.fold
+      ~string:(fun x -> [Markup x])
+      ~section:
+        (fun ~inverted name contents -> [Section { inverted ; name ; contents }])
+      ~escaped:(fun x -> [Pcdata x])
+      ~unescaped:(fun x -> [Expr x])
+      ~partial:
+        (fun s -> of_mustache resolve @@ mustache_from_file @@ resolve s)
+      ~comment:(fun _ -> [])
+      ~concat:List.concat
+
+  let bindings ~env ~sec_env ~id =
+    let f s b b' = match b, b' with
+      | Some k, Some k' ->
+        if Var.equal k k' then None
+        else raise @@ Location.Error (Var.error s k k')
+      | None, Some k' -> Some k'
+      | _, None -> None
+    in
+    let env = Var.Env.merge f env sec_env in
+    let make_binding k _ l =
+      Vb.mk (AC.pvar k) (Exp.send id k) :: l
+    in
+    Exp.let_ Asttypes.Nonrecursive @@ Var.Env.fold make_binding env []
+
+  let rec desc_to_expr ~loc ~lang env t =
+    Ast_helper.default_loc := loc ;
+    match (t : desc) with
+    | Markup s -> env, AC.str s
+    | Pcdata s ->
+      Var.add env s Var, antiquot_pcdata ~loc ~lang s
+    | Expr s ->
+      Var.add env s Expr, AC.evar s
+    | Section { inverted ; name ; contents } ->
+      let sec_env, e =
+        to_expr ~simplify:false ~loc ~lang Var.Env.empty contents
+      in
+      let env = Var.section env name sec_env in
+      let id = AC.evar name in
+      let pid = AC.pvar name in
+      if inverted then
+        env, [%expr if [%e id] = [] then [] else [%e e]]
+      else
+        let e = bindings ~env ~sec_env ~id e in
+        env, [%expr List.concat (List.map (fun [%p pid] -> [%e e]) [%e id])]
+
+  and to_expr ~simplify ~loc ~lang env l =
+    let f (env, acc) t =
+      let env, expr = desc_to_expr ~loc ~lang env t in
+      env, expr::acc
+    in
+    let env, l = List.fold_left f (env, []) l in
+    env, Ppx_tyxml.markup_to_expr ~simplify lang loc @@ List.rev l
+
+  let make_function env e =
+    let f s _k e =
+      Exp.fun_ (AC.Label.labelled s) None (AC.pvar s) e
+    in
+    Var.Env.fold f env e
+
+end
+
+let list_as_app = function
+  | [] -> AC.unit ()
+  | h :: t -> Exp.apply h (List.map (fun x -> AC.Label.nolabel, x) t)
+
+let expr_of_mustache ~loc ~lang t =
+  let env, e =
+    Template.to_expr ~simplify:true ~loc ~lang Var.Env.empty @@
+    Template.of_mustache (fun _s -> assert false) @@
+    t
+  in
+  Template.make_function env e
+
+let expr_of_string ~loc ~lang s =
+  expr_of_mustache ~loc ~lang @@
+  mustache_from_string ~loc:loc.loc_start s
+
+
+(** Mappers *)
+
+open Parsetree
+
+let error loc =
+  Ppx_common.error loc "Invalid payload for [%%template]."
+
+let extract_str loc str = match AC.get_str str with
+  | None -> error loc
+  | Some s -> s
+
+let expr mapper e =
+  let loc = e.pexp_loc in
+  match e.pexp_desc with
+  | Pexp_extension ({ txt = ("template" | "tyxml.template")}, payload) ->
+    begin match payload with
+      | PStr [[%stri let [%p? var] = [%e? str] in [%e? e]]] ->
+        let s = extract_str loc str in
+        Exp.let_ Asttypes.Nonrecursive
+          [Vb.mk var @@ expr_of_string ~loc:str.pexp_loc ~lang:Html s]
+          e
+
+      | PStr [{pstr_desc = Pstr_eval (str, _)}] ->
+        let s = extract_str loc str in
+        expr_of_string ~loc:str.pexp_loc ~lang:Html s
+
+      | _ -> error loc
+    end
+  | _ -> Ast_mapper.default_mapper.expr mapper e
+
+let structure_item mapper stri =
+  let loc = stri.pstr_loc in
+  match stri.pstr_desc with
+  | Pstr_extension (({ txt = ("template" | "tyxml.template")}, payload), _) ->
+    begin match payload with
+      | PStr [[%stri let [%p? var] = [%e? str]]] ->
+        let s = extract_str loc str in
+        Str.value Asttypes.Nonrecursive
+          [Vb.mk var @@ expr_of_string ~loc:str.pexp_loc ~lang:Html s]
+      | _ -> error loc
+    end
+  | _ -> Ast_mapper.default_mapper.structure_item mapper stri
+
+let mapper _ =
+  { Ast_mapper. default_mapper with expr ; structure_item }
+
+let () = Ast_mapper.register "tyxml.template" mapper

mustache/tymustache.ml

@@ -0,0 +1 @@
+