Parser: Use implicit ending for tags

They are not necessarily at the end anymore, and the end similarly as light
syntax list: on new lines or heading.

This is a breaking change, which according to ocaml#1138 is fixing more things than
breaking them.
It will allow using custom tags and tags in mld files.

Author: panglesd

src/parser/syntax.ml

@@ -580,7 +580,7 @@ type ('block, 'stops_at_which_tokens) context =
   | In_explicit_list : (Ast.nestable_block_element, stops_at_delimiters) context
   | In_table_cell : (Ast.nestable_block_element, stops_at_delimiters) context
   | In_code_results : (Ast.nestable_block_element, code_stop) context
-  | In_tag : (Ast.nestable_block_element, Token.t) context
+  | In_tag : (Ast.nestable_block_element, stopped_implicitly) context
 
 (* This is a no-op. It is needed to prove to the type system that nestable block
    elements are acceptable block elements in all contexts. *)
@@ -638,13 +638,12 @@ let rec block_element_list :
     * where_in_line =
  fun context ~parent_markup input ->
   let rec consume_block_elements :
-      parsed_a_tag:bool ->
       where_in_line ->
       block with_location list ->
       block with_location list
       * stops_at_which_tokens with_location
       * where_in_line =
-   fun ~parsed_a_tag where_in_line acc ->
+   fun where_in_line acc ->
     let describe token =
       match token with
       | #token_that_always_begins_an_inline_element -> "paragraph"
@@ -657,16 +656,6 @@ let rec block_element_list :
         |> add_warning input
     in
 
-    let warn_if_after_tags { Loc.location; value = token } =
-      if parsed_a_tag then
-        let suggestion =
-          Printf.sprintf "move %s before any tags." (Token.describe token)
-        in
-        Parse_error.not_allowed ~what:(describe token)
-          ~in_what:"the tags section" ~suggestion location
-        |> add_warning input
-    in
-
     let warn_because_not_at_top_level { Loc.location; value = token } =
       let suggestion =
         Printf.sprintf "move %s outside of any other markup."
@@ -700,31 +689,33 @@ let rec block_element_list :
         | In_tag -> (List.rev acc, next_token, where_in_line)
         | In_code_results ->
             junk input;
-            consume_block_elements ~parsed_a_tag where_in_line acc)
+            consume_block_elements where_in_line acc)
     | { value = `Right_code_delimiter; _ } as next_token -> (
         match context with
         | In_code_results -> (List.rev acc, next_token, where_in_line)
         | _ ->
             junk input;
-            consume_block_elements ~parsed_a_tag where_in_line acc)
+            consume_block_elements where_in_line acc)
     (* Whitespace. This can terminate some kinds of block elements. It is also
        necessary to track it to interpret [`Minus] and [`Plus] correctly, as
        well as to ensure that all block elements begin on their own line. *)
     | { value = `Space _; _ } ->
         junk input;
-        consume_block_elements ~parsed_a_tag where_in_line acc
+        consume_block_elements where_in_line acc
     | { value = `Single_newline _; _ } ->
         junk input;
-        consume_block_elements ~parsed_a_tag `At_start_of_line acc
+        consume_block_elements `At_start_of_line acc
     | { value = `Blank_line _; _ } as next_token -> (
         match context with
-        (* Blank lines terminate shorthand lists ([- foo]). They also terminate
-           paragraphs, but the paragraph parser is aware of that internally. *)
+        (* Blank lines terminate shorthand lists ([- foo]) and tags. They also
+           terminate paragraphs, but the paragraph parser is aware of that
+           internally. *)
         | In_shorthand_list -> (List.rev acc, next_token, where_in_line)
+        | In_tag -> (List.rev acc, next_token, where_in_line)
         (* Otherwise, blank lines are pretty much like single newlines. *)
         | _ ->
             junk input;
-            consume_block_elements ~parsed_a_tag `At_start_of_line acc)
+            consume_block_elements `At_start_of_line acc)
     (* Explicit list items ([{li ...}] and [{- ...}]) can never appear directly
        in block content. They can only appear inside [{ul ...}] and [{ol ...}].
        So, catch those. *)
@@ -740,7 +731,7 @@ let rec block_element_list :
         |> add_warning input;
 
         junk input;
-        consume_block_elements ~parsed_a_tag where_in_line acc
+        consume_block_elements where_in_line acc
     (* Table rows ([{tr ...}]) can never appear directly
        in block content. They can only appear inside [{table ...}]. *)
     | { value = `Begin_table_row as token; location } ->
@@ -753,7 +744,7 @@ let rec block_element_list :
           ~suggestion location
         |> add_warning input;
         junk input;
-        consume_block_elements ~parsed_a_tag where_in_line acc
+        consume_block_elements where_in_line acc
     (* Table cells ([{th ...}] and [{td ...}]) can never appear directly
        in block content. They can only appear inside [{tr ...}]. *)
     | { value = `Begin_table_cell _ as token; location } ->
@@ -766,9 +757,8 @@ let rec block_element_list :
           ~suggestion location
         |> add_warning input;
         junk input;
-        consume_block_elements ~parsed_a_tag where_in_line acc
-    (* Tags. These can appear at the top level only. Also, once one tag is seen,
-       the only top-level elements allowed are more tags. *)
+        consume_block_elements where_in_line acc
+    (* Tags. These can appear at the top level only. *)
     | { value = `Tag tag as token; location } as next_token -> (
         let recover_when_not_at_top_level context =
           warn_because_not_at_top_level next_token;
@@ -779,8 +769,7 @@ let rec block_element_list :
             |> accepted_in_all_contexts context
             |> Loc.at location
           in
-          consume_block_elements ~parsed_a_tag `At_start_of_line
-            (paragraph :: acc)
+          consume_block_elements `At_start_of_line (paragraph :: acc)
         in
 
         match context with
@@ -831,8 +820,7 @@ let rec block_element_list :
                 in
 
                 let tag = Loc.at location (`Tag tag) in
-                consume_block_elements ~parsed_a_tag:true `After_text
-                  (tag :: acc)
+                consume_block_elements `After_text (tag :: acc)
             | (`Deprecated | `Return) as tag ->
                 let content, _stream_head, where_in_line =
                   block_element_list In_tag ~parent_markup:token input
@@ -846,8 +834,7 @@ let rec block_element_list :
                   location :: List.map Loc.location content |> Loc.span
                 in
                 let tag = Loc.at location (`Tag tag) in
-                consume_block_elements ~parsed_a_tag:true where_in_line
-                  (tag :: acc)
+                consume_block_elements where_in_line (tag :: acc)
             | (`Param _ | `Raise _ | `Before _) as tag ->
                 let content, _stream_head, where_in_line =
                   block_element_list In_tag ~parent_markup:token input
@@ -862,8 +849,7 @@ let rec block_element_list :
                   location :: List.map Loc.location content |> Loc.span
                 in
                 let tag = Loc.at location (`Tag tag) in
-                consume_block_elements ~parsed_a_tag:true where_in_line
-                  (tag :: acc)
+                consume_block_elements where_in_line (tag :: acc)
             | `See (kind, target) ->
                 let content, _next_token, where_in_line =
                   block_element_list In_tag ~parent_markup:token input
@@ -873,23 +859,19 @@ let rec block_element_list :
                 in
                 let tag = `Tag (`See (kind, target, content)) in
                 let tag = Loc.at location tag in
-                consume_block_elements ~parsed_a_tag:true where_in_line
-                  (tag :: acc)
+                consume_block_elements where_in_line (tag :: acc)
             | (`Inline | `Open | `Closed | `Hidden) as tag ->
                 let tag = Loc.at location (`Tag tag) in
-                consume_block_elements ~parsed_a_tag:true `After_text
-                  (tag :: acc)))
+                consume_block_elements `After_text (tag :: acc)))
     | ( { value = #token_that_always_begins_an_inline_element; _ }
       | { value = `Bar; _ } ) as next_token ->
-        warn_if_after_tags next_token;
         warn_if_after_text next_token;
 
         let block = paragraph input in
         let block = Loc.map (accepted_in_all_contexts context) block in
         let acc = block :: acc in
-        consume_block_elements ~parsed_a_tag `After_text acc
+        consume_block_elements `After_text acc
     | { value = `Verbatim s as token; location } as next_token ->
-        warn_if_after_tags next_token;
         warn_if_after_text next_token;
         if s = "" then
           Parse_error.should_not_be_empty ~what:(Token.describe token) location
@@ -899,9 +881,8 @@ let rec block_element_list :
         let block = accepted_in_all_contexts context token in
         let block = Loc.at location block in
         let acc = block :: acc in
-        consume_block_elements ~parsed_a_tag `After_text acc
+        consume_block_elements `After_text acc
     | { value = `Math_block s as token; location } as next_token ->
-        warn_if_after_tags next_token;
         warn_if_after_text next_token;
         if s = "" then
           Parse_error.should_not_be_empty ~what:(Token.describe token) location
@@ -911,14 +892,13 @@ let rec block_element_list :
         let block = accepted_in_all_contexts context token in
         let block = Loc.at location block in
         let acc = block :: acc in
-        consume_block_elements ~parsed_a_tag `After_text acc
+        consume_block_elements `After_text acc
     | {
         value =
           `Code_block (meta, delim, { value = s; location = v_loc }, has_outputs)
           as token;
         location;
       } as next_token ->
-        warn_if_after_tags next_token;
         warn_if_after_text next_token;
         junk input;
         let delimiter = if delim = "" then None else Some delim in
@@ -958,9 +938,8 @@ let rec block_element_list :
         in
         let block = Loc.at location block in
         let acc = block :: acc in
-        consume_block_elements ~parsed_a_tag `After_text acc
+        consume_block_elements `After_text acc
     | { value = `Modules s as token; location } as next_token ->
-        warn_if_after_tags next_token;
         warn_if_after_text next_token;
 
         junk input;
@@ -999,9 +978,8 @@ let rec block_element_list :
         let block = accepted_in_all_contexts context (`Modules modules) in
         let block = Loc.at location block in
         let acc = block :: acc in
-        consume_block_elements ~parsed_a_tag `After_text acc
+        consume_block_elements `After_text acc
     | { value = `Begin_list kind as token; location } as next_token ->
-        warn_if_after_tags next_token;
         warn_if_after_text next_token;
 
         junk input;
@@ -1018,10 +996,9 @@ let rec block_element_list :
         let block = accepted_in_all_contexts context block in
         let block = Loc.at location block in
         let acc = block :: acc in
-        consume_block_elements ~parsed_a_tag `After_text acc
+        consume_block_elements `After_text acc
     | { value = (`Begin_table_light | `Begin_table_heavy) as token; location }
       as next_token ->
-        warn_if_after_tags next_token;
         warn_if_after_text next_token;
         junk input;
         let block, brace_location =
@@ -1037,7 +1014,7 @@ let rec block_element_list :
         let block = accepted_in_all_contexts context (`Table block) in
         let block = Loc.at location block in
         let acc = block :: acc in
-        consume_block_elements ~parsed_a_tag `After_text acc
+        consume_block_elements `After_text acc
     | { value = (`Minus | `Plus) as token; location } as next_token -> (
         (match where_in_line with
         | `After_text | `After_shorthand_bullet ->
@@ -1046,8 +1023,6 @@ let rec block_element_list :
             |> add_warning input
         | _ -> ());
 
-        warn_if_after_tags next_token;
-
         match context with
         | In_shorthand_list -> (List.rev acc, next_token, where_in_line)
         | _ ->
@@ -1064,11 +1039,9 @@ let rec block_element_list :
             let block = accepted_in_all_contexts context block in
             let block = Loc.at location block in
             let acc = block :: acc in
-            consume_block_elements ~parsed_a_tag where_in_line acc)
+            consume_block_elements where_in_line acc)
     | { value = `Begin_section_heading (level, label) as token; location } as
       next_token -> (
-        warn_if_after_tags next_token;
-
         let recover_when_not_at_top_level context =
           warn_because_not_at_top_level next_token;
           junk input;
@@ -1083,8 +1056,7 @@ let rec block_element_list :
             |> accepted_in_all_contexts context
             |> Loc.at location
           in
-          consume_block_elements ~parsed_a_tag `At_start_of_line
-            (paragraph :: acc)
+          consume_block_elements `At_start_of_line (paragraph :: acc)
         in
 
         match context with
@@ -1094,7 +1066,10 @@ let rec block_element_list :
             else recover_when_not_at_top_level context
         | In_explicit_list -> recover_when_not_at_top_level context
         | In_table_cell -> recover_when_not_at_top_level context
-        | In_tag -> recover_when_not_at_top_level context
+        | In_tag ->
+            if where_in_line = `At_start_of_line then
+              (List.rev acc, next_token, where_in_line)
+            else recover_when_not_at_top_level context
         | In_code_results -> recover_when_not_at_top_level context
         | Top_level ->
             if where_in_line <> `At_start_of_line then
@@ -1127,7 +1102,7 @@ let rec block_element_list :
             let heading = `Heading (level, label, content) in
             let heading = Loc.at location heading in
             let acc = heading :: acc in
-            consume_block_elements ~parsed_a_tag `After_text acc)
+            consume_block_elements `After_text acc)
     | { value = `Begin_paragraph_style _ as token; location } ->
         junk input;
         let content, brace_location =
@@ -1146,13 +1121,11 @@ let rec block_element_list :
           |> accepted_in_all_contexts context
           |> Loc.at location
         in
-        consume_block_elements ~parsed_a_tag `At_start_of_line (paragraph :: acc)
+        consume_block_elements `At_start_of_line (paragraph :: acc)
     | {
-        location;
-        value = `Media_with_replacement_text (href, media, content) as token;
-      } as next_token ->
-        warn_if_after_tags next_token;
-
+     location;
+     value = `Media_with_replacement_text (href, media, content) as token;
+    } ->
         junk input;
 
         let r_location =
@@ -1181,10 +1154,8 @@ let rec block_element_list :
         let block = accepted_in_all_contexts context block in
         let block = Loc.at location block in
         let acc = block :: acc in
-        consume_block_elements ~parsed_a_tag `After_text acc
-    | { location; value = `Simple_media (href, media) } as next_token ->
-        warn_if_after_tags next_token;
-
+        consume_block_elements `After_text acc
+    | { location; value = `Simple_media (href, media) } ->
         junk input;
 
         let r_location =
@@ -1198,7 +1169,7 @@ let rec block_element_list :
         let block = accepted_in_all_contexts context block in
         let block = Loc.at location block in
         let acc = block :: acc in
-        consume_block_elements ~parsed_a_tag `After_text acc
+        consume_block_elements `After_text acc
   in
 
   let where_in_line =
@@ -1211,7 +1182,7 @@ let rec block_element_list :
     | In_tag -> `After_tag
   in
 
-  consume_block_elements ~parsed_a_tag:false where_in_line []
+  consume_block_elements where_in_line []
 
 (* {3 Lists} *)