fix: the tests were not passing anymore

Due to recent deep-but-small changes, some tests were not passing anymore.
This commit fixes what is important to fix, the test battery is not fully passing but the cases with known issues are minor issues.

Implementation details: this fix mainly concerns `\n`-related issues at the backend level.

modified:   omd_backend.ml
modified:   omd_parser.ml

Author: pw374

src/omd_backend.ml

@@ -221,6 +221,7 @@ let rec html_and_headers_of_md
               loop indent tl
           end
       end
+    | Paragraph [] :: tl -> loop indent tl
     | Paragraph md as e :: tl ->
       begin match override e with
         | Some s ->
@@ -234,7 +235,7 @@ let rec html_and_headers_of_md
              begin
                Buffer.add_string b "<p>";
                Buffer.add_string b (remove_trailing_blanks s);
-               Buffer.add_string b "</p>";
+               Buffer.add_string b "</p>\n";
              end);
           loop indent tl
       end
@@ -876,14 +877,15 @@ let rec markdown_of_md md =
     | Img_ref(rc, name, alt, fallback) :: tl ->
         if !references = None then references := Some rc;
         loop list_indent (Raw(fallback#to_string)::tl)
+    | Paragraph [] :: tl -> loop list_indent tl
     | Paragraph md :: tl ->
       if is_in_list then
         if fst_p_in_li then
           add_spaces (list_indent-2)
         else
           add_spaces list_indent;
       loop ~fst_p_in_li:false list_indent md;
-      if tl <> [] then Printf.bprintf b "\n\n";
+      Printf.bprintf b "\n\n";
       loop ~fst_p_in_li:false list_indent tl
     | Img(alt, src, title) :: tl ->
       Printf.bprintf b "![%s](%s \"%s\")" alt src title;
@@ -1071,8 +1073,8 @@ let rec markdown_of_md md =
     | (Html_block(tagname, attrs, body))::tl ->
       let is_p =
         match tl with
-        | NL :: Paragraph _ :: _
-        | Paragraph _ :: _ -> true
+        | NL :: Paragraph p :: _
+        | Paragraph p :: _ -> p <> []
         | _ -> false
       in
       if body = [] && StringSet.mem tagname html_void_elements then
@@ -1137,9 +1139,10 @@ let rec markdown_of_md md =
       Buffer.add_string b "\n";
       loop list_indent tl
     | NL :: tl ->
-      if Buffer.length b > 1 &&
-         not(Buffer.nth b (Buffer.length b - 1) = '\n'
-              && Buffer.nth b (Buffer.length b - 2) = '\n')
+      if Buffer.length b = 1
+      || (Buffer.length b > 1 &&
+          not(Buffer.nth b (Buffer.length b - 1) = '\n'
+              && Buffer.nth b (Buffer.length b - 2) = '\n'))
       then
       Buffer.add_string b "\n";
       loop list_indent tl

src/omd_parser.ml

@@ -620,8 +620,6 @@ struct
         List.rev accu
       | Blockquote b1 :: Blockquote b2 :: tl ->
         loop cp accu (Blockquote(b1@b2):: tl)
-      | Blockquote b1 :: (NL|Br as x) :: Blockquote b2 :: tl ->
-        loop cp accu (Blockquote(b1@(x::b2)):: tl)
       | Blockquote b :: tl ->
         let e = Blockquote(loop [] [] b) in
         (match cp with
@@ -2163,13 +2161,16 @@ let read_until_space ?(bq=false) ?(no_nl=false) l =
       | Newline::Greaterthan::Spaces n::tl ->
         assert(n>0);
         loop (Newline::cl@block) [Spaces(n-1)] tl
+
+      (* multi paragraph blockquotes with empty lines *)
       | Newlines 0::Greaterthan::Space::tl ->
         loop (Newlines 0::cl@block) [] tl
       | Newlines 0::Greaterthan::Spaces 0::tl ->
         loop (Newlines 0::cl@block) [Space] tl
       | Newlines 0::Greaterthan::Spaces n::tl ->
         assert(n>0);
         loop (Newlines 0::cl@block) [Spaces(n-1)] tl
+
       | (Newlines _::_ as l) | ([] as l) -> fix(List.rev(cl@block)), l
       | e::tl -> loop block (e::cl) tl
     in