improved validation logic for dot operator commands

Author: SudhansuBandha

lib/repl.js

@@ -815,12 +815,12 @@ class REPLServer extends Interface {
         const dotIndex = StringPrototypeIndexOf(trimmedCmd, '.');
         const isDotCommandAfterWhitespace = dotIndex > 0 &&
                                             StringPrototypeCharAt(trimmedCmd, dotIndex + 1) !== '.';
-
-        if ((isDotCommandAtStart || isDotCommandAfterWhitespace) &&
+        const matches = RegExpPrototypeExec(/(?:^|\s)\.([^\s]+)\s*(.*)$/, trimmedCmd);
+        const keyword = matches?.[1];
+        const rest = matches?.[2];
+        const isValidKeyword = keyword && ObjectKeys(self.commands).includes(keyword);
+        if ((isDotCommandAtStart || isDotCommandAfterWhitespace && isValidKeyword) &&
             NumberIsNaN(NumberParseFloat(trimmedCmd))) {
-          const matches = RegExpPrototypeExec(/(?:^|\s)\.([^\s]+)\s*(.*)$/, trimmedCmd);
-          const keyword = matches?.[1];
-          const rest = matches?.[2];
           if (FunctionPrototypeCall(_parseREPLKeyword, self, keyword, rest) === true) {
             return;
           }

test/parallel/test-repl-multiline-dot-commands-execution.js

@@ -13,9 +13,11 @@ function runDotCommand(command, validate) {
 
   replServer.on('exit', common.mustCall());
   replServer.write('function a() {\n');
+  replServer.write('console.log("logging");\n');
   replServer.write(`${command}\n`);
   validate(replServer, output);
   replServer.write('arr = [1,\n');
+  replServer.write('console.log("logging");\n');
   replServer.write(`${command}\n`);
   validate(replServer, output);
   replServer.close();