Frontmatter: raise on duplicated @children_order entry

Author: panglesd

src/model/frontmatter.ml

@@ -13,7 +13,9 @@ let apply fm line =
   | Children_order children_order, { children_order = None } ->
       { children_order = Some (Location_.same line children_order) }
   | Children_order _, { children_order = Some _ } ->
-      (* TODO raise warning about duplicate children field *) fm
+      Error.raise_warning
+        (Error.make "Duplicated @children_order entry" line.location);
+      fm
 
 let parse_child c =
   if Astring.String.is_suffix ~affix:"/" c then
@@ -39,4 +41,5 @@ let parse_children_order loc co =
       Error
         (Error.make "Only words are accepted when specifying children order" loc)
 
-let of_lines lines = List.fold_left apply empty lines
+let of_lines lines =
+  Error.catch_warnings @@ fun () -> List.fold_left apply empty lines

src/model/frontmatter.mli

@@ -13,4 +13,4 @@ val parse_children_order :
   Odoc_parser.Ast.nestable_block_element Location_.with_location list ->
   (line Location_.with_location, Error.t) result
 
-val of_lines : line Location_.with_location list -> t
+val of_lines : line Location_.with_location list -> t Error.with_warnings

src/model/semantics.ml

@@ -44,7 +44,7 @@ let rec find_tag f = function
           find_tag f tl)
 
 let rec find_tags acc f = function
-  | [] -> acc
+  | [] -> List.rev acc
   | hd :: tl -> (
       match f hd.Location.value with
       | Some x -> find_tags ((x, hd.location) :: acc) f tl
@@ -85,7 +85,7 @@ let handle_internal_tags (type a) tags : a handle_internal_tags -> a = function
                     None))
           unparsed_lines
       in
-      Frontmatter.of_lines lines
+      Frontmatter.of_lines lines |> Error.raise_warnings
   | Expect_none ->
       (* Will raise warnings. *)
       ignore (find_tag (fun _ -> None) tags);

test/frontmatter/frontmatter.t/run.t

@@ -56,20 +56,22 @@ When there is one frontmatter, it is extracted from the content:
     }
   ]
 
-When there is more than one children order, the last one:
+When there is more than one children order, we raise a warning and keep only the first entry:
 
   $ odoc compile two_frontmatters.mld
+  File "two_frontmatters.mld", line 5, characters 0-25:
+  Warning: Duplicated @children_order entry
   File "two_frontmatters.mld":
   Warning: Non-index page cannot specify (children _) in the frontmatter.
   $ odoc_print page-two_frontmatters.odoc | jq '.frontmatter'
   {
     "children": {
       "Some": [
         {
-          "Page": "bli3"
+          "Page": "bli1"
         },
         {
-          "Page": "bli4"
+          "Page": "bli2"
         }
       ]
     }