emoji: avoid crashing whole server on broken JSON

It may still crash due to a race condition between checking for file
existence and opening/streaming, but File.stream! has no safe version
we can use to avoid this completely.
Just not deleting such files during a reload is easy enough.

lib/pleroma/emoji.ex

@@ -76,9 +76,6 @@ def get_all do
     :ets.tab2list(@ets)
   end
 
-  @doc "Clear out old emojis"
-  def clear_all, do: :ets.delete_all_objects(@ets)
-
   @doc false
   def init(_) do
     @ets = :ets.new(@ets, @ets_options)
@@ -109,7 +106,10 @@ def code_change(_old_vsn, state, _extra) do
     {:ok, state}
   end
 
+  defp update_emojis([]), do: true
+
   defp update_emojis(emojis) do
+    :ets.delete_all_objects(@ets)
     :ets.insert(@ets, emojis)
   end
 

lib/pleroma/emoji/loader.ex

@@ -69,7 +69,6 @@ def load do
               load_pack(Path.join(emoji_dir_path, pack), emoji_groups)
             end)
 
-          Emoji.clear_all()
           emojis
       end
 
@@ -104,13 +103,9 @@ defp load_pack(pack_dir, emoji_groups) do
 
     if File.exists?(pack_file) do
       Logger.debug("Loading emoji pack from JSON: #{pack_file}")
-      contents = Jason.decode!(File.read!(pack_file))
 
-      contents["files"]
-      |> Enum.map(fn {name, rel_file} ->
-        filename = Path.join("/emoji/#{pack_name}", rel_file)
-        {name, filename, ["pack:#{pack_name}"]}
-      end)
+      Jason.decode(File.read!(pack_file))
+      |> load_from_pack(pack_name)
     else
       # Load from emoji.txt / all files
       emoji_txt = Path.join(pack_dir, "emoji.txt")
@@ -135,6 +130,21 @@ defp load_pack(pack_dir, emoji_groups) do
     end
   end
 
+  defp load_from_pack({:ok, %{"files" => files}}, pack_name) when is_map(files) do
+    Enum.map(files, fn {name, rel_file} ->
+      filename = Path.join("/emoji/#{pack_name}", rel_file)
+      {name, filename, ["pack:#{pack_name}"]}
+    end)
+  end
+
+  defp load_from_pack(pack_json_result, pack_name) do
+    Logger.error(
+      "Failed to load emoji pack #{pack_name} from pack.json:\n#{inspect(pack_json_result)}"
+    )
+
+    []
+  end
+
   def make_shortcode_to_file_map(pack_dir, exts) do
     find_all_emoji(pack_dir, exts)
     |> Enum.map(&Path.relative_to(&1, pack_dir))