FIX: Do not optimize animated images in cooked posts (#11214)

CookedPostProcessor replaces all large images with their optimized
versions, but for GIF images the optimized version is limited to first
frame only. This caused animations it cooked posts to require a click
to show up the lightbox and start playing.

lib/cooked_post_processor.rb

@@ -384,7 +384,7 @@ class CookedPostProcessor
     w, h = img["width"].to_i, img["height"].to_i
 
     # note: optimize_urls cooks the src and data-small-upload further after this
-    thumbnail = upload.thumbnail(w, h)
+    thumbnail = !upload.animated && upload.thumbnail(w, h)
     if thumbnail && thumbnail.filesize.to_i < upload.filesize
       img["src"] = thumbnail.url
 

spec/components/cooked_post_processor_spec.rb

@@ -960,6 +960,19 @@ describe CookedPostProcessor do
       expect(doc.css('img').first['srcset']).to_not eq(nil)
     end
 
+    it "does not optimize animated images" do
+      upload.update!(animated: true)
+      post = Fabricate(:post, raw: "![image|1024x768, 50%](#{upload.short_url})")
+
+      cpp = CookedPostProcessor.new(post, disable_loading_image: true)
+      cpp.post_process
+
+      doc = Nokogiri::HTML5::fragment(cpp.html)
+      expect(doc.css('.lightbox-wrapper').size).to eq(1)
+      expect(doc.css('img').first['src']).to include(upload.url)
+      expect(doc.css('img').first['srcset']).to eq(nil)
+    end
+
     it "optimizes images in quotes" do
       post = Fabricate(:post, raw: <<~MD)
         [quote]