node: allow preload modules with -i

This gives us the ability to preload when using the node repl. This can
be useful for doing things like creating aliases.

Fixes: #4661
PR-URL: #4696
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

src/node.js

@@ -140,6 +140,7 @@
         }
 
       } else {
+        startup.preloadModules();
         // If -i or --interactive were passed, or stdin is a TTY.
         if (process._forceRepl || NativeModule.require('tty').isatty(0)) {
           // REPL

test/fixtures/define-global.js

@@ -0,0 +1 @@
+global.a = 'test';

test/parallel/test-preload.js

@@ -1,5 +1,5 @@
 'use strict';
-require('../common');
+const common = require('../common');
 const assert = require('assert');
 const path = require('path');
 const child_process = require('child_process');
@@ -21,6 +21,7 @@ var fixture = function(name) {
 var fixtureA = fixture('printA.js');
 var fixtureB = fixture('printB.js');
 var fixtureC = fixture('printC.js');
+const fixtureD = fixture('define-global.js');
 var fixtureThrows = fixture('throws_error4.js');
 
 // test preloading a single module works
@@ -73,6 +74,18 @@ child_process.exec(nodeBinary + ' '
     assert.equal(stdout, 'A\nB\nhello\n');
   });
 
+// test that preload works with -i
+const interactive = child_process.exec(nodeBinary + ' '
+  + preloadOption([fixtureD])
+  + '-i',
+  common.mustCall(function(err, stdout, stderr) {
+    assert.ifError(err);
+    assert.strictEqual(stdout, `> 'test'\n> `);
+  }));
+
+interactive.stdin.write('a\n');
+interactive.stdin.write('process.exit()\n');
+
 child_process.exec(nodeBinary + ' '
   + '--require ' + fixture('cluster-preload.js') + ' '
   + fixture('cluster-preload-test.js'),