buffer: throw exception when creating from non-Node.js Context

Throw an exception instead of crashing when attempting to create
`Buffer` objects from a Context that is not associated with
a Node.js `Environment`.

Possible alternatives for the future might be just returning
a plain `Uint8Array`, or working on providing `Buffer` for all
`Context`s.

PR-URL: https://github.com/nodejs/node/pull/23938
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Daniel Bevenius <daniel.bevenius@gmail.com>

2 files changed, 36 insertions, 7 deletions

diff --git a/test/addons/non-node-context/binding.cc b/test/addons/non-node-context/binding.cc
index 324f5c5a1e..776786cef5 100644
--- a/test/addons/non-node-context/binding.cc
+++ b/test/addons/non-node-context/binding.cc
@@ -1,4 +1,5 @@
 #include <node.h>
+#include <node_buffer.h>
 #include <assert.h>
 
 namespace {
@@ -15,6 +16,17 @@ using v8::Script;
 using v8::String;
 using v8::Value;
 
+inline void MakeBufferInNewContext(
+    const v8::FunctionCallbackInfo<v8::Value>& args) {
+  Isolate* isolate = args.GetIsolate();
+  Local<Context> context = Context::New(isolate);
+  Context::Scope context_scope(context);
+
+  // This should throw an exception, rather than actually do anything.
+  MaybeLocal<Object> buf = node::Buffer::Copy(isolate, "foo", 3);
+  assert(buf.IsEmpty());
+}
+
 inline void RunInNewContext(
     const v8::FunctionCallbackInfo<v8::Value>& args) {
   Isolate* isolate = args.GetIsolate();
@@ -41,13 +53,8 @@ inline void RunInNewContext(
 inline void Initialize(Local<Object> exports,
                        Local<Value> module,
                        Local<Context> context) {
-  Isolate* isolate = context->GetIsolate();
-  Local<String> key = String::NewFromUtf8(
-      isolate, "runInNewContext", NewStringType::kNormal).ToLocalChecked();
-  Local<Function> value = FunctionTemplate::New(isolate, RunInNewContext)
-                   ->GetFunction(context)
-                   .ToLocalChecked();
-  assert(exports->Set(context, key, value).IsJust());
+  NODE_SET_METHOD(exports, "runInNewContext", RunInNewContext);
+  NODE_SET_METHOD(exports, "makeBufferInNewContext", MakeBufferInNewContext);
 }
 
 }  // anonymous namespace
diff --git a/test/addons/non-node-context/test-make-buffer.js b/test/addons/non-node-context/test-make-buffer.js
new file mode 100644
index 0000000000..9b17fa4ee9
--- /dev/null
+++ b/test/addons/non-node-context/test-make-buffer.js
@@ -0,0 +1,22 @@
+'use strict';
+
+const common = require('../../common');
+const assert = require('assert');
+const {
+  makeBufferInNewContext
+} = require(`./build/${common.buildType}/binding`);
+
+// Because the `Buffer` function and its protoype property only (currently)
+// exist in a Node.js instance’s main context, trying to create buffers from
+// another context throws an exception.
+
+try {
+  makeBufferInNewContext();
+} catch (exception) {
+  assert.strictEqual(exception.constructor.name, 'Error');
+  assert(!(exception.constructor instanceof Error));
+
+  assert.strictEqual(exception.code, 'ERR_BUFFER_CONTEXT_NOT_AVAILABLE');
+  assert.strictEqual(exception.message,
+                     'Buffer is not available for the current Context');
+}