FIX: apply diffs more consistently

1. Do escaping direct in diff streamer, that way HTML tags and other unsafe chars can be displayed and fixed
2. Add safeguard to ensure streaming always stops when it was terminated elsewhere

Author: SamSaffron

assets/javascripts/discourse/components/modal/diff-modal.gjs

@@ -24,8 +24,8 @@ export default class ModalDiffModal extends Component {
 
   @tracked loading = false;
   @tracked finalResult = "";
-  @tracked selectedText = escapeExpression(this.args.model.selectedText);
-  @tracked diffStreamer = new DiffStreamer(this.selectedText);
+  @tracked escapedSelectedText = escapeExpression(this.args.model.selectedText);
+  @tracked diffStreamer = new DiffStreamer(this.args.model.selectedText);
   @tracked suggestion = "";
   @tracked
   smoothStreamer = new SmoothStreamer(
@@ -45,11 +45,16 @@ export default class ModalDiffModal extends Component {
 
     // Prevents flash by showing the
     // original text when the diff is empty
-    return this.selectedText;
+    return this.escapedSelectedText;
   }
 
   get isStreaming() {
-    return this.diffStreamer.isStreaming || this.smoothStreamer.isStreaming;
+    // diffStreamer stops "streaming" when it is finished with a chunk
+    return (
+      this.diffStreamer.isStreaming ||
+      !this.diffStreamer.isDone ||
+      this.smoothStreamer.isStreaming
+    );
   }
 
   get primaryBtnLabel() {
@@ -105,7 +110,7 @@ export default class ModalDiffModal extends Component {
         data: {
           location: "composer",
           mode: this.args.model.mode,
-          text: this.selectedText,
+          text: this.args.model.selectedText,
           custom_prompt: this.args.model.customPromptValue,
           force_default_locale: true,
           client_id: this.messageBus.clientId,
@@ -122,7 +127,7 @@ export default class ModalDiffModal extends Component {
 
     if (this.suggestion) {
       this.args.model.toolbarEvent.replaceText(
-        this.selectedText,
+        this.args.model.selectedText,
         this.suggestion
       );
     }
@@ -131,8 +136,12 @@ export default class ModalDiffModal extends Component {
       this.finalResult?.length > 0
         ? this.finalResult
         : this.diffStreamer.suggestion;
+
     if (this.args.model.showResultAsDiff && finalResult) {
-      this.args.model.toolbarEvent.replaceText(this.selectedText, finalResult);
+      this.args.model.toolbarEvent.replaceText(
+        this.args.model.selectedText,
+        finalResult
+      );
     }
   }
 

assets/javascripts/discourse/lib/diff-streamer.gjs

@@ -2,8 +2,9 @@ import { tracked } from "@glimmer/tracking";
 import { cancel, later } from "@ember/runloop";
 import loadJSDiff from "discourse/lib/load-js-diff";
 import { parseAsync } from "discourse/lib/text";
+import { escapeExpression } from "discourse/lib/utilities";
 
-const DEFAULT_CHAR_TYPING_DELAY = 30;
+const DEFAULT_CHAR_TYPING_DELAY = 10;
 const STREAMING_DIFF_TRUNCATE_THRESHOLD = 0.1;
 const STREAMING_DIFF_TRUNCATE_BUFFER = 10;
 
@@ -51,7 +52,7 @@ export default class DiffStreamer {
 
       const originalDiff = this.jsDiff.diffWordsWithSpace(
         this.selectedText,
-        this.suggestion
+        newText
       );
       this.diff = this.#formatDiffWithTags(originalDiff, false);
       return;
@@ -172,6 +173,10 @@ export default class DiffStreamer {
   }
 
   async #streamNextChar() {
+    if (!this.isStreaming || this.isDone) {
+      return;
+    }
+
     if (this.currentWordIndex < this.words.length) {
       const currentToken = this.words[this.currentWordIndex];
 
@@ -252,6 +257,7 @@ export default class DiffStreamer {
     return `<span>${text}</span>`;
   }
 
+  // returns an HTML safe diff (escaping all internals)
   #formatDiffWithTags(diffArray, highlightLastWord = true) {
     const wordsWithType = [];
     const output = [];
@@ -280,7 +286,8 @@ export default class DiffStreamer {
     }
 
     for (let i = 0; i <= lastWordIndex; i++) {
-      const { text, type } = wordsWithType[i];
+      let { text, type } = wordsWithType[i];
+      text = escapeExpression(text);
 
       if (/^\s+$/.test(text)) {
         output.push(text);
@@ -310,6 +317,7 @@ export default class DiffStreamer {
           i++;
         }
 
+        chunkText = escapeExpression(chunkText);
         output.push(this.#wrapChunk(chunkText, chunkType));
       }
     }