fix: use private block scope RegExp instead of shared module scope RegExp

Author: Theo-Steiner

lib/internal/readline/interface.js

@@ -20,6 +20,7 @@ const {
   MathMaxApply,
   NumberIsFinite,
   ObjectSetPrototypeOf,
+  RegExp,
   RegExpPrototypeExec,
   StringPrototypeCodePointAt,
   StringPrototypeEndsWith,
@@ -72,7 +73,7 @@ const kHistorySize = 30;
 const kMaxUndoRedoStackSize = 2048;
 const kMincrlfDelay = 100;
 // \r\n, \n, or \r followed by something other than \n
-const lineEnding = /\r?\n|\r(?!\n)/g;
+const lineEndingPattern = '\r?\n|\r(?!\n)';
 
 const kLineObjectStream = Symbol('line object stream');
 const kQuestionCancel = Symbol('kQuestionCancel');
@@ -585,6 +586,7 @@ class Interface extends InterfaceConstructor {
     }
 
     // Run test() on the new string chunk, not on the entire line buffer.
+    const lineEnding = new RegExp(lineEndingPattern, 'g');
     let newPartContainsEnding = RegExpPrototypeExec(lineEnding, string);
     if (newPartContainsEnding !== null) {
       if (this[kLine_buffer]) {
@@ -1322,18 +1324,24 @@ class Interface extends InterfaceConstructor {
         // falls through
         default:
           if (typeof s === 'string' && s) {
+            /**
+             * Use Regular Expression scoped to this block, as lastIndex and the state for RegExpPrototypeExec
+             * will be overwritten if the same RegEx instance is reused in recursive function calls.
+             */
+            const lineEnding = new RegExp(lineEndingPattern, 'g');
             let nextMatch = RegExpPrototypeExec(lineEnding, s);
-            if (nextMatch !== null) {
-              this[kInsertString](StringPrototypeSlice(s, 0, nextMatch.index));
-              let { lastIndex } = lineEnding;
-              while ((nextMatch = RegExpPrototypeExec(lineEnding, s)) !== null) {
-                this[kLine]();
+
+            // If no line endings are found, just insert the string as is
+            if (nextMatch === null) {
+              this[kInsertString](s);
+            } else {
+              // Keep track of the end of the last match
+              let lastIndex = 0;
+              do {
                 this[kInsertString](StringPrototypeSlice(s, lastIndex, nextMatch.index));
+                this[kLine]();
                 ({ lastIndex } = lineEnding);
-              }
-              if (lastIndex === s.length) this[kLine]();
-            } else {
-              this[kInsertString](s);
+              } while ((nextMatch = RegExpPrototypeExec(lineEnding, s)) !== null);
             }
           }
       }

lib/repl.js

@@ -862,7 +862,7 @@ function REPLServer(prompt,
       const matches = self._sawKeyPress ?
         RegExpPrototypeExec(/^\s+/, cmd) : null;
       // Preserve indentation in editorMode
-      if (matches && !self.loadMode) {
+      if (matches) {
         const prefix = matches[0];
         self.write(prefix);
         self.line = prefix;
@@ -1780,11 +1780,9 @@ function defineDefaultCommands(repl) {
         const stats = fs.statSync(file);
         if (stats && stats.isFile()) {
           _turnOnEditorMode(this);
-          this.loadMode = true;
           const data = fs.readFileSync(file, 'utf8');
           this.write(data);
           _turnOffEditorMode(this);
-          this.loadMode = false;
           this.write('\n');
         } else {
           this.output.write(
@@ -1793,7 +1791,6 @@ function defineDefaultCommands(repl) {
         }
       } catch {
         this.output.write(`Failed to load: ${file}\n`);
-        this.loadMode = false;
       }
       this.displayPrompt();
     }