repl: preprocess only for defaultEval

Code preprocessing is applicable only for default
eval function. Therefore, Moved `preprocess` function
invocation inside `defaultEval` function.

Fixes: https://github.com/nodejs/node/issues/9743
PR-URL: https://github.com/nodejs/node/pull/9752
Reviewed-By: Anna Henningsen <anna@addaleax.net>

lib/repl.js

@@ -238,7 +238,33 @@ function REPLServer(prompt,
 
   eval_ = eval_ || defaultEval;
 
+  function preprocess(code) {
+    let cmd = code;
+    if (/^\s*\{/.test(cmd) && /\}\s*$/.test(cmd)) {
+      // It's confusing for `{ a : 1 }` to be interpreted as a block
+      // statement rather than an object literal.  So, we first try
+      // to wrap it in parentheses, so that it will be interpreted as
+      // an expression.
+      cmd = `(${cmd})`;
+      self.wrappedCmd = true;
+    } else {
+      // Mitigate https://github.com/nodejs/node/issues/548
+      cmd = cmd.replace(
+        /^\s*function(?:\s*(\*)\s*|\s+)([^(]+)/,
+        (_, genStar, name) => `var ${name} = function ${genStar || ''}${name}`
+      );
+    }
+    // Append a \n so that it will be either
+    // terminated, or continued onto the next expression if it's an
+    // unexpected end of input.
+    return `${cmd}\n`;
+  }
+
   function defaultEval(code, context, file, cb) {
+    // Remove trailing new line
+    code = code.replace(/\n$/, '');
+    code = preprocess(code);
+
     var err, result, retry = false, input = code, wrappedErr;
     // first, create the Script object to check the syntax
 
@@ -506,8 +532,7 @@ function REPLServer(prompt,
       }
     }
 
-    var evalCmd = self.bufferedCommand + cmd;
-    evalCmd = preprocess(evalCmd);
+    const evalCmd = self.bufferedCommand + cmd + '\n';
 
     debug('eval %j', evalCmd);
     self.eval(evalCmd, self.context, 'repl', finish);
@@ -564,28 +589,6 @@ function REPLServer(prompt,
       // Display prompt again
       self.displayPrompt();
     }
-
-    function preprocess(code) {
-      let cmd = code;
-      if (/^\s*\{/.test(cmd) && /\}\s*$/.test(cmd)) {
-        // It's confusing for `{ a : 1 }` to be interpreted as a block
-        // statement rather than an object literal.  So, we first try
-        // to wrap it in parentheses, so that it will be interpreted as
-        // an expression.
-        cmd = `(${cmd})`;
-        self.wrappedCmd = true;
-      } else {
-        // Mitigate https://github.com/nodejs/node/issues/548
-        cmd = cmd.replace(
-          /^\s*function(?:\s*(\*)\s*|\s+)([^(]+)/,
-          (_, genStar, name) => `var ${name} = function ${genStar || ''}${name}`
-        );
-      }
-      // Append a \n so that it will be either
-      // terminated, or continued onto the next expression if it's an
-      // unexpected end of input.
-      return `${cmd}\n`;
-    }
   });
 
   self.on('SIGCONT', function() {

test/parallel/test-repl-eval.js

@@ -10,7 +10,8 @@ const repl = require('repl');
     eval: common.mustCall((cmd, context) => {
       // Assertions here will not cause the test to exit with an error code
       // so set a boolean that is checked in process.on('exit',...) instead.
-      evalCalledWithExpectedArgs = (cmd === 'foo\n' && context.foo === 'bar');
+      evalCalledWithExpectedArgs = (cmd === 'function f() {}\n' &&
+                                    context.foo === 'bar');
     })
   };
 
@@ -18,7 +19,12 @@ const repl = require('repl');
   r.context = {foo: 'bar'};
 
   try {
-    r.write('foo\n');
+    // Default preprocessor transforms
+    //  function f() {}  to
+    //  var f = function f() {}
+    // Test to ensure that original input is preserved.
+    // Reference: https://github.com/nodejs/node/issues/9743
+    r.write('function f() {}\n');
   } finally {
     r.write('.exit\n');
   }