vm: run runInThisContext() in last entered context

Change `vm.runInThisContext()` to use the last entered context, not the
top-level context that `vm.runInThisContext()` belongs to.

Note the call chain:

    1. `node::ContextifyScript::RunInThisContext()`
    2. `node::ContextifyScript::EvalMachine()`
    3. `v8::Script::BindToCurrentContext()`

The current context in `RunInThisContext()` is that of the top-level
context which was then bound to the script to execute.

It works when `vm.runInThisContext()` is called from the top-level
context (the common case and hence why this bug went unnoticed for
so long) but not when called from an inferior context.

As a pleasant side effect, this commit fixes a bug in the REPL where
writes to `process.stdout` and `process.stderr` still went to the real
stdout and stderr instead of being captured redirected.

Fixes previously failing test `known_issues/test-repl-require-context`
which has been moved to `test/parallel` and renamed to avoid a conflict
with an existing test of the same name.

Note that this commit changes the behavior of the following snippet:

    const s = '(function() { return vm.runInThisContext(this) })()';
    const f = vm.runInNewContext(s, vm);
    f();

Before this commit, it returned the |this| of the new context, now
it returns the |this| of the enclosing context.  Two steps forward,
one step back.

Fixes: nodejs#7788
Refs: nodejs#14757

Author: bnoordhuis

src/node_contextify.cc

@@ -652,7 +652,10 @@ class ContextifyScript : public BaseObject {
     bool display_errors = maybe_display_errors.ToChecked();
     bool break_on_sigint = maybe_break_on_sigint.ToChecked();
 
-    // Do the eval within this context
+    auto context = args.GetIsolate()->GetEnteredContext();
+    if (context.IsEmpty()) context = env->context();
+    Context::Scope context_scope(context);
+
     EvalMachine(env, timeout, display_errors, break_on_sigint, args,
                 &try_catch);
   }

test/known_issues/test-vm-eval-run-in-new-context.js

@@ -0,0 +1,13 @@
+// Refs: https://github.com/nodejs/node/issues/14757
+'use strict';
+const common = require('../common');
+const assert = require('assert');
+const vm = require('vm');
+
+{
+  const s = '(function() { return [this, runInThisContext("this")] })';
+  const f = vm.runInNewContext(s, vm);
+  const [that0, that1] = f();
+  assert.strictEqual(that0, that1);
+  assert.notEqual(that0, global);
+}

test/known_issues/test-repl-require-context.js test/parallel/test-repl-require-context-2.js

@@ -30,5 +30,6 @@ server.listen(options, function() {
 process.on('exit', function() {
   assert.strictEqual(false, /Cannot find module/.test(answer));
   assert.strictEqual(false, /Error/.test(answer));
-  assert.strictEqual(answer, '\'eye catcher\'\n\'perhaps I work\'\n');
+  assert(answer.includes('\'eye catcher\'\n\'perhaps I work\'\n'));
+  assert(answer.includes('node_modules'));  // Printed by the loaded modules.
 });

test/parallel/test-repl-require.js

@@ -456,7 +456,11 @@ function tcp_test() {
           expect: (`12346\n${prompt_tcp}`) },
         { client: client_tcp,
           send: `require(${JSON.stringify(moduleFilename)}).number`,
-          expect: (`42\n${prompt_tcp}`) }
+          expect: (`load fixtures/b/d.js\n` +
+                   `load package/index.js\n` +
+                   `load fixtures/b/c.js\n` +
+                   `load fixtures/a.js\n` +
+                   `42\n${prompt_tcp}`) }
       ]);
     });
 

test/parallel/test-repl.js

@@ -73,3 +73,13 @@ const fn = vm.runInNewContext('(function() { obj.p = {}; })', { obj: {} });
 global.gc();
 fn();
 // Should not crash
+
+// https://github.com/nodejs/node/issues/14757 - vm.runInNewContext() should
+// use the last entered context, not the context that vm.runInNewContext()
+// belongs to (which is the top level context.)
+{
+  const [that0, that1] =
+      vm.runInNewContext('[this, runInThisContext("this")]', vm);
+  assert.strictEqual(that0, that1);
+  assert.notEqual(that0, global);
+}