repl: refactor repl.js

There is some unnecessary logic in repl.js. Remove it.

PR-URL: #6071
Reviewed-By: James M Snell <jasnell@gmail.com>

lib/repl.js

@@ -398,7 +398,6 @@ function REPLServer(prompt,
   self.on('line', function(cmd) {
     debug('line %j', cmd);
     sawSIGINT = false;
-    var skipCatchall = false;
 
     // leading whitespaces in template literals should not be trimmed.
     if (self._inTemplateLiteral) {
@@ -417,11 +416,12 @@ function REPLServer(prompt,
         return;
       } else if (!self.bufferedCommand) {
         self.outputStream.write('Invalid REPL keyword\n');
-        skipCatchall = true;
+        finish(null);
+        return;
       }
     }
 
-    if (!skipCatchall && (cmd || (!cmd && self.bufferedCommand))) {
+    if (cmd || self.bufferedCommand) {
       var evalCmd = self.bufferedCommand + cmd;
       if (/^\s*\{/.test(evalCmd) && /\}\s*$/.test(evalCmd)) {
         // It's confusing for `{ a : 1 }` to be interpreted as a block
@@ -1022,7 +1022,7 @@ REPLServer.prototype.memory = function memory(cmd) {
     // self.lines.level.length === 0
     // TODO? keep a log of level so that any syntax breaking lines can
     // be cleared on .break and in the case of a syntax error?
-    // TODO? if a log was kept, then I could clear the bufferedComand and
+    // TODO? if a log was kept, then I could clear the bufferedCommand and
     // eval these lines and throw the syntax error
   } else {
     self.lines.level = [];

test/parallel/test-repl-null.js

@@ -0,0 +1,17 @@
+'use strict';
+require('../common');
+const repl = require('repl');
+const assert = require('assert');
+
+var replserver = new repl.REPLServer();
+
+replserver._inTemplateLiteral = true;
+
+// `null` gets treated like an empty string. (Should it? You have to do some
+// strange business to get it into the REPL. Maybe it should really throw?)
+
+assert.doesNotThrow(() => {
+  replserver.emit('line', null);
+});
+
+replserver.emit('line', '.exit');