Fix handling of rdf:langString in media summary and name (#39590)

app/helpers/json_ld_helper.rb

@@ -17,6 +17,22 @@ module JsonLdHelper
     value.is_a?(Array) ? value.first : value
   end
 
+  # Some attributes we read can be either `xsd:string` or `rdf:langString`
+  # and will lead to different compacted forms depending on which they are.
+  # Furthermore, we don't unconditionally compact to our context, so we
+  # may also find non-compacted forms.
+  # This is the case of `summary`, `name` and `content` as defined in ActivityStreams.
+  def first_lang_string(json, name)
+    if json[name]
+      value = first_of_value(json[name])
+      return value if value.is_a?(String)
+
+      value['@value'] if value.is_a?(Hash)
+    elsif json["#{name}Map"]
+      json["#{name}Map"].values.first
+    end
+  end
+
   def uri_from_bearcap(str)
     if str&.start_with?('bear:')
       Addressable::URI.parse(str).query_values['u']

app/lib/activitypub/parser/media_attachment_parser.rb

@@ -29,7 +29,7 @@ class ActivityPub::Parser::MediaAttachmentParser
   end
 
   def description
-    str = @json['summary'].presence || @json['name'].presence
+    str = first_lang_string(@json, 'summary').presence || first_lang_string(@json, 'name').presence
     str = str.strip[0...MediaAttachment::MAX_DESCRIPTION_HARD_LENGTH_LIMIT] if str.present?
     str
   end

app/services/activitypub/process_account_service.rb

@@ -256,7 +256,7 @@ class ActivityPub::ProcessAccountService < BaseService
     if value.is_a?(Hash) && value['type'] == 'Image'
       url = first_of_value(value['url'])
       url = url['href'] if url.is_a?(Hash)
-      description = value['summary'].presence || value['name'].presence
+      description = first_lang_string(value, 'summary').presence || first_lang_string(value, 'name').presence
       description = description.strip[0...MediaAttachment::MAX_DESCRIPTION_HARD_LENGTH_LIMIT] if description.present?
     else
       url = value