FIX: handle quote rendering for external Discourse instance (#16722)

Gracefully handle quotes from an external discourse instance by stripping quote-controls and including username in the title

app/assets/javascripts/discourse/app/widgets/post-cooked.js

@@ -282,6 +282,11 @@ export default class PostCooked {
         this._updateQuoteElements($aside, "chevron-down");
         const $title = $(".title", $aside);
 
+        // If post/topic is not found then display username, skip controls
+        if (e.classList.contains("quote-post-not-found")) {
+          return (e.querySelector(".title").innerHTML = e.dataset.username);
+        }
+
         // Unless it's a full quote, allow click to expand
         if (!($aside.data("full") || $title.data("has-quote-controls"))) {
           $title.on("click", (e2) => {

lib/cooked_post_processor.rb

@@ -78,9 +78,8 @@ class CookedPostProcessor
           q.css('blockquote').text
         )
 
-        if comparer.modified?
-          q['class'] = ((q['class'] || '') + " quote-modified").strip
-        end
+        q['class'] = ((q['class'] || '') + " quote-post-not-found").strip if comparer.missing?
+        q['class'] = ((q['class'] || '') + " quote-modified").strip if comparer.modified?
       end
     end
   end

lib/quote_comparer.rb

@@ -15,12 +15,18 @@ class QuoteComparer
   # This algorithm is far from perfect, but it follows the Discourse
   # philosophy of "catch the obvious cases, leave moderation for the
   # complicated ones"
+  def missing?
+    return true if @parent_post.blank?
+  end
+
   def modified?
-    return true if @text.blank? || @parent_post.blank?
+    return true if @text.blank?
 
-    parent_text = Nokogiri::HTML5::fragment(@parent_post.cooked).text.delete(QuoteComparer.whitespace)
-    text = @text.delete(QuoteComparer.whitespace)
+    if @parent_post
+      parent_text = Nokogiri::HTML5::fragment(@parent_post.cooked).text.delete(QuoteComparer.whitespace)
+      text = @text.delete(QuoteComparer.whitespace)
 
-    !parent_text.include?(text)
+      !parent_text.include?(text)
+    end
   end
 end

spec/lib/cooked_post_processor_spec.rb

@@ -1753,6 +1753,22 @@ describe CookedPostProcessor do
       end
     end
 
+    context "external discourse instance quote" do
+      let(:external_raw) do
+        <<~RAW.strip
+        [quote="random_guy_not_from_our_discourse, post:2004, topic:401"]
+        this quote is not from our discourse
+        [/quote]
+        and this is a reply
+        RAW
+      end
+      let(:cp) { Fabricate(:post, raw: external_raw) }
+
+      it "it should be marked as missing" do
+        cpp.post_process_quotes
+        expect(cpp.doc.css('aside.quote.quote-post-not-found')).to be_present
+      end
+    end
   end
 
   context "full quote on direct reply" do

spec/lib/quote_comparer_spec.rb

@@ -4,6 +4,30 @@ require 'quote_comparer'
 
 describe QuoteComparer do
 
+  describe "#missing?" do
+    fab!(:post) { Fabricate(:post, raw: "This has **text** we _are_ matching") }
+
+    it "returns true for missing topic and post" do
+      expect(QuoteComparer.new(nil, nil, "test")).to be_missing
+    end
+
+    it "returns true for missing topic" do
+      expect(QuoteComparer.new(nil, post.post_number, "test")).to be_missing
+    end
+
+    it "returns true for missing post" do
+      expect(QuoteComparer.new(post.topic_id, nil, "test")).to be_missing
+    end
+
+    it "returns false for only missing text" do
+      expect(QuoteComparer.new(post.topic_id, post.post_number, nil)).to_not be_missing
+    end
+
+    it "returns false for no missing topic and post" do
+      expect(QuoteComparer.new(post.topic_id, post.post_number, "test")).to_not be_missing
+    end
+  end
+
   describe "#modified?" do
     fab!(:post) { Fabricate(:post, raw: "This has **text** we _are_ matching") }
 
@@ -11,10 +35,6 @@ describe QuoteComparer do
       QuoteComparer.new(post.topic_id, post.post_number, text)
     end
 
-    it "returns true for no post" do
-      expect(QuoteComparer.new(nil, nil, "test")).to be_modified
-    end
-
     it "returns true for nil text" do
       expect(qc(nil)).to be_modified
     end