Add frontmatter to page's root

This allows to load it without loading the whole content. Requires extracting
the frontmatter types to avoid cyclic dependencies.

Author: panglesd

src/model/frontmatter.ml

@@ -0,0 +1 @@
+type t = (string * string) list

src/model/lang.ml

@@ -527,10 +527,6 @@ end =
 module rec Page : sig
   type child = Page_child of string | Module_child of string
 
-  module Frontmatter : sig
-    type t = (string * string) list
-  end
-
   type t = {
     name : Identifier.Page.t;
     root : Root.t;

src/model/root.ml

@@ -29,7 +29,11 @@ end
 module Odoc_file = struct
   type compilation_unit = { name : string; hidden : bool }
 
-  type page = { name : string; title : Comment.link_content option }
+  type page = {
+    name : string;
+    title : Comment.link_content option;
+    frontmatter : Frontmatter.t option;
+  }
 
   type t =
     | Page of page
@@ -41,7 +45,7 @@ module Odoc_file = struct
     let hidden = force_hidden || Names.contains_double_underscore name in
     Compilation_unit { name; hidden }
 
-  let create_page name title = Page { name; title }
+  let create_page name title frontmatter = Page { name; title; frontmatter }
 
   let create_impl name = Impl name
 

src/model/root.mli

@@ -28,7 +28,11 @@ end
 module Odoc_file : sig
   type compilation_unit = { name : string; hidden : bool }
 
-  type page = { name : string; title : Comment.link_content option }
+  type page = {
+    name : string;
+    title : Comment.link_content option;
+    frontmatter : Frontmatter.t option;
+  }
 
   type t =
     | Page of page
@@ -38,7 +42,8 @@ module Odoc_file : sig
 
   val create_unit : force_hidden:bool -> string -> t
 
-  val create_page : string -> Comment.link_content option -> t
+  val create_page :
+    string -> Comment.link_content option -> Frontmatter.t option -> t
 
   val create_impl : string -> t
 

src/model_desc/lang_desc.ml

@@ -697,6 +697,10 @@ and page_t =
     [
       F ("name", (fun t -> t.name), identifier);
       F ("root", (fun t -> t.root), root);
+      F
+        ( "frontmatter",
+          (fun t -> t.frontmatter),
+          Option (List (Pair (string, string))) );
       F ("content", (fun t -> t.content), docs);
       F ("digest", (fun t -> t.digest), Digest.t);
     ]

src/odoc/compile.ml

@@ -240,7 +240,9 @@ let mld ~parent_id ~parents_children ~output ~children ~warnings_options input =
     let zero_heading = Comment.find_zero_heading content in
     let frontmatter, content = Comment.extract_frontmatter content in
     let root =
-      let file = Root.Odoc_file.create_page root_name zero_heading in
+      let file =
+        Root.Odoc_file.create_page root_name zero_heading frontmatter
+      in
       { Root.id = (name :> Paths.Identifier.OdocId.t); file; digest }
     in
     let page =

src/odoc/html_fragment.ml

@@ -9,13 +9,15 @@ let from_mld ~xref_base_uri ~resolver ~output ~warnings_options input =
   in
   let input_s = Fs.File.to_string input in
   let digest = Digest.file input_s in
-  let root =
-    let file = Odoc_model.Root.Odoc_file.create_page page_name None in
-    { Odoc_model.Root.id; file; digest }
-  in
   let to_html content =
     (* This is a mess. *)
     let frontmatter, content = Odoc_model.Comment.extract_frontmatter content in
+    let root =
+      let file =
+        Odoc_model.Root.Odoc_file.create_page page_name None frontmatter
+      in
+      { Odoc_model.Root.id; file; digest }
+    in
     let page =
       Odoc_model.Lang.Page.
         {