print headings as bold

lib/mrkdwn.ml

@@ -110,8 +110,21 @@ module Cmarkit_slack = struct
       | Inline.Link (l, _) -> link c l
       | _ -> false (* let the default renderer handle that *)
     in
+    let block c block =
+      let open Cmarkit in
+      let module C = Cmarkit_renderer.Context in
+      match block with
+      | Block.Heading (heading, _) ->
+        let inline = Block.Heading.inline heading in
+        C.byte c '*';
+        C.inline c inline;
+        C.byte c '*';
+        C.byte c '\n';
+        true
+      | _ -> false
+    in
     let default_renderer = Cmarkit_commonmark.renderer () in
-    let renderer = Cmarkit_renderer.make ~inline () in
+    let renderer = Cmarkit_renderer.make ~inline ~block () in
     Cmarkit_renderer.compose default_renderer renderer
 end
 

lib_test/mrkdwn/mrkdwn_of_md.t

@@ -28,3 +28,19 @@ link
   > [hello](https://google.be)
   > MD
   <https://google.be|hello>
+
+headings
+  $ mrkdwn_of_md << "MD"
+  > # one
+  > ## two
+  > ### three
+  > #### four
+  > ##### five
+  > ###### six
+  > MD
+  *one*
+  *two*
+  *three*
+  *four*
+  *five*
+  *six*