FIX: Quoting a quote preserves the original post information (#8746)

Let's say post #2 quotes post number #1. If a user decides to quote the
quote in post #2, it should keep the information of post #1
("user_1, post: 1, topic: X"), instead of replacing with current post
info ("user_2, post: 2, topic: X").

app/assets/javascripts/discourse/components/quote-button.js.es6

@@ -1,7 +1,7 @@
 import { scheduleOnce } from "@ember/runloop";
 import Component from "@ember/component";
 import discourseDebounce from "discourse/lib/debounce";
-import { selectedText } from "discourse/lib/utilities";
+import { selectedText, selectedElement } from "discourse/lib/utilities";
 
 export default Component.extend({
   classNames: ["quote-button"],
@@ -48,8 +48,28 @@ export default Component.extend({
       }
     }
 
+    let opts;
+    for (
+      let element = selectedElement();
+      element && element.tagName !== "ARTICLE";
+      element = element.parentElement
+    ) {
+      if (element.tagName === "ASIDE" && element.classList.contains("quote")) {
+        opts = {
+          username:
+            element.dataset.username ||
+            element
+              .querySelector(".title")
+              .textContent.trim()
+              .replace(/:$/, ""),
+          post: element.dataset.post,
+          topic: element.dataset.topic
+        };
+      }
+    }
+
     const _selectedText = selectedText();
-    quoteState.selected(postId, _selectedText);
+    quoteState.selected(postId, _selectedText, opts);
     this.set("visible", quoteState.buffer.length > 0);
 
     // avoid hard loops in quote selection unconditionally
@@ -165,8 +185,8 @@ export default Component.extend({
   },
 
   click() {
-    const { postId, buffer } = this.quoteState;
-    this.attrs.selectText(postId, buffer).then(() => this._hideButton());
+    const { postId, buffer, opts } = this.quoteState;
+    this.attrs.selectText(postId, buffer, opts).then(() => this._hideButton());
     return false;
   }
 });

app/assets/javascripts/discourse/controllers/topic.js.es6

@@ -266,7 +266,7 @@ export default Controller.extend(bufferedProperty("model"), {
       this.send("showFeatureTopic");
     },
 
-    selectText(postId, buffer) {
+    selectText(postId, buffer, opts) {
       const loadedPost = this.get("model.postStream").findLoadedPost(postId);
       const promise = loadedPost
         ? Promise.resolve(loadedPost)
@@ -275,7 +275,7 @@ export default Controller.extend(bufferedProperty("model"), {
       return promise.then(post => {
         const composer = this.composer;
         const viewOpen = composer.get("model.viewOpen");
-        const quotedText = Quote.build(post, buffer);
+        const quotedText = Quote.build(post, buffer, opts);
 
         // If we can't create a post, delegate to reply as new topic
         if (!viewOpen && !this.get("model.details.can_create_post")) {

app/assets/javascripts/discourse/lib/quote-state.js.es6

@@ -3,13 +3,15 @@ export default class QuoteState {
     this.clear();
   }
 
-  selected(postId, buffer) {
+  selected(postId, buffer, opts) {
     this.postId = postId;
     this.buffer = buffer;
+    this.opts = opts;
   }
 
   clear() {
     this.buffer = "";
     this.postId = null;
+    this.opts = null;
   }
 }

app/assets/javascripts/discourse/lib/quote.js.es6

@@ -8,6 +8,7 @@ export default {
     }
 
     if (!contents) contents = "";
+    if (!opts) opts = {};
 
     const sansQuotes = contents.replace(this.REGEXP, "").trim();
     if (sansQuotes.length === 0) {
@@ -26,9 +27,9 @@ export default {
       stripped.replace(/\W/g, "") === contents.replace(/\W/g, "");
 
     const params = [
-      post.get("username"),
-      `post:${post.get("post_number")}`,
-      `topic:${post.get("topic_id")}`
+      opts.username || post.username,
+      `post:${opts.post || post.post_number}`,
+      `topic:${opts.topic || post.topic_id}`
     ];
 
     opts = opts || {};

app/assets/javascripts/discourse/lib/utilities.js.es6

@@ -143,6 +143,13 @@ export function selectedText() {
   return toMarkdown($div.html());
 }
 
+export function selectedElement() {
+  const selection = window.getSelection();
+  if (selection.rangeCount > 0) {
+    return selection.getRangeAt(0).startContainer.parentElement;
+  }
+}
+
 // Determine the row and col of the caret in an element
 export function caretRowCol(el) {
   var cp = caretPosition(el);

app/assets/javascripts/pretty-text/engines/discourse-markdown/quotes.js.es6

@@ -73,6 +73,10 @@ const rule = {
       token.attrs.push(["class", "quote no-group"]);
     }
 
+    if (username) {
+      token.attrs.push(["data-username", username]);
+    }
+
     if (postNumber) {
       token.attrs.push(["data-post", postNumber]);
     }