Improve error handling in abacus-eval (cloudfoundry-attic#610)

Author: stoyanr

lib/utils/eval/src/index.js

@@ -42,8 +42,12 @@ const xeval = (s, c) => {
     }
   }
   catch (ex) {
-    edebug('Evaluating expression %s with context %o and timeout %d' + 
-      ' using %s failed with %s', s, context, timeout, vmtype, ex);
+    if (s === 'f(...args)' && c.f && c.args)
+      edebug('Calling function %s with arguments %o and timeout %d using %s' +
+        ' failed with %s', c.f.toString(), c.args, timeout, vmtype, ex);
+    else
+      edebug('Evaluating expression %s with context %o and timeout %d' +
+        ' using %s failed with %s', s, context, timeout, vmtype, ex);
     throw ex;
   }
 };
@@ -66,9 +70,16 @@ const check = (s) => {
 // using strict mode, and return a new function that calls the above function, 
 // also in a sandbox
 const xevalfn = (s, c) => {
-  check(s);
-  const f = xeval('"use strict"; (' + s + ')', c);
-  return (...args) => xeval('f(...args)', { f: f, args: args });
+  try {
+    check(s);
+    const f = xeval('"use strict"; (' + s + ')', c);
+    return (...args) => xeval('f(...args)', { f: f, args: args });
+  }
+  catch (ex) {
+    return (...args) => {
+      throw ex;
+    };
+  }
 };
 
 // Export our public functions

lib/utils/eval/src/test/test.js

@@ -50,10 +50,12 @@ async.each(['vm', 'vm2'], (vmtype, cb) => {
       });
 
       it('prevents asynchronus execution with Promises', () => {
-        expect(() => xeval(`() => {
+        const f = xeval(`() => {
           return new Promise((resolve, reject) => resolve())
             .then(function(value) { while(true); })
-        }`)).to.throw('Promises not supported');
+        }`);
+        expect(typeof f).to.equal('function');
+        expect(f).to.throw('Promises not supported');
       });
 
       it('prevents direct usage of built-in modules and globals', () => {
@@ -63,8 +65,9 @@ async.each(['vm', 'vm2'], (vmtype, cb) => {
       });
 
       it('prevents requiring modules', () => {
-        expect(xeval('() => require("console").log("Hi")')).to.throw(
-          'require is not defined');
+        const f = xeval('() => require("console").log("Hi")');
+        expect(typeof f).to.equal('function');
+        expect(f).to.throw('require is not defined');
       });
 
       vm2it('prevents escaping via this.constructor.constructor', () => {
@@ -87,7 +90,9 @@ async.each(['vm', 'vm2'], (vmtype, cb) => {
       });
 
       it('rejects arguments.callee', () => {
-        expect(xeval('function (x) { return arguments.callee; }')).to.throw(
+        const f = xeval('function (x) { return arguments.callee; }');
+        expect(typeof f).to.equal('function');
+        expect(f).to.throw(
           '\'caller\', \'callee\', and \'arguments\' properties ' +
           'may not be accessed on strict mode functions or the arguments ' +
           'objects for calls to them');