Add a workaround for new Buffer () and some tests

Author: josephjclark

packages/runtime/src/execute/context.ts

@@ -21,6 +21,19 @@ export default (
 ) => {
   const logger = options.jobLogger ?? console;
   const globals = options.globals || {};
+
+  // Workaround for https://github.com/nodejs/node/issues/4660
+  // The Buffer class we share directly with users will throw if used
+  // All _internal_ Buffer references use the original nodejs interface
+  class SafeBuffer extends Buffer {
+    constructor(x: any) {
+      throw new Error(
+        'Do not call Buffer() constructor directly. Use Buffer.from() instead.'
+      );
+      super(x); // keeps types happy
+    }
+  }
+
   const context = vm.createContext(
     freezeAll(
       {
@@ -34,7 +47,7 @@ export default (
         setInterval,
         setTimeout,
         state, // TODO will be dropped as a global one day, see https://github.com/OpenFn/kit/issues/17
-        Buffer,
+        Buffer: SafeBuffer,
       },
       { state: true }
     ),

packages/runtime/test/context.test.ts

@@ -60,3 +60,27 @@ test("doesn't allow eval inside a job", async (t) => {
     message: /Illegal eval statement detected/,
   });
 });
+
+test('Buffer.from() works inside a job', async (t) => {
+  const expression = `
+    export default [
+      (s) => { s.data = Buffer.from('6a6f65', 'hex').toString(); return s;  }
+    ];`;
+  const input = {};
+
+  const result = await run(expression, input);
+  t.is(result.data as any, 'joe');
+});
+
+test('Buffer constructor throws inside a job', async (t) => {
+  const expression = `
+    export default [
+      (s) => { s.data = new Buffer('6a6f65', 'hex').toString(); return s;  }
+    ];`;
+  const input = {};
+
+  const result = await run(expression, input);
+  const err = result.errors!['job-1'];
+  t.is(err.name, 'JobError');
+  t.regex(err.message, /do not call Buffer\(\) constructor/i);
+});