fix: Increase yaml Buffer to Fix Video Scraper (#3392)

* increase yaml library buffer to fix video scraper

* fmt

Author: sabine

tool/ood-gen/lib/youtube.ml

@@ -187,17 +187,33 @@ let scrape yaml_file =
   in
   match fetched with
   | Ok fetched ->
-      let yaml =
+      let all_videos =
         VideoSet.union fetched scraped
         |> VideoSet.to_seq |> List.of_seq
         |> List.sort (fun a b -> compare b.Vid.published a.Vid.published)
-        |> Vid.video_list_to_yaml
       in
+      let yaml = Vid.video_list_to_yaml all_videos in
+      (* The yaml library uses a fixed-size output buffer. The default is 262140
+         bytes, which was exceeded when we had 203 videos (~262KB output). This
+         caused the document_end operation to fail with "doc_end failed" error.
+
+         Current stats: 203 videos ≈ 260KB, average ~1.3KB per video. We use a
+         2MB buffer to accommodate growth to ~1500 videos before hitting limits.
+         If the list grows beyond that, this will fail with a clear error
+         message. *)
+      let buffer_size = 2 * 1024 * 1024 in
+      (* 2MB *)
       let output =
-        Yaml.pp Format.str_formatter yaml;
-        Format.flush_str_formatter ()
+        match Yaml.to_string ~len:buffer_size yaml with
+        | Ok s -> s
+        | Error (`Msg err) ->
+            failwith
+              (Printf.sprintf
+                 "YAML serialization failed (tried %d videos, buffer size %d \
+                  bytes): %s"
+                 (List.length all_videos) buffer_size err)
       in
       let oc = open_out yaml_file in
-      Printf.fprintf oc "%s" output;
+      output_string oc output;
       close_out oc
   | Error (`Msg msg) -> failwith msg