call next returnHandler even if errors occurred

src/index.js

@@ -39,6 +39,15 @@ class RpcEngine extends SafeEventEmitter {
     }
     // process all middleware
     this._runMiddleware(req, res, (err) => {
+      // take a clear any responseError
+      const responseError = res._originalError
+      delete res._originalError
+      if (responseError) {
+        // ensure no result is present on an errored response
+        delete res.result
+        // return originalError and response
+        return cb(responseError, res)
+      }
       // return response
       cb(err, res)
     })
@@ -96,7 +105,11 @@ class RpcEngine extends SafeEventEmitter {
         cb()
       }
       function end (err) {
-        if (err) return cb(err)
+        // if errored, set the error but dont pass to callback
+        if (err) {
+          res.error = serializeError(err)
+          res._originalError = err
+        }
         // mark as completed
         isComplete = true
         cb()
@@ -105,12 +118,10 @@ class RpcEngine extends SafeEventEmitter {
 
     // returns, indicating whether or not it ended
     function completeRequest (err) {
+      // this is an internal catastrophic error, not an error from middleware
       if (err) {
         // prepare error message
-        res.error = {
-          code: err.code || -32603,
-          message: err.stack,
-        }
+        res.error = serializeError(err)
         // return error-first and res with err
         return onDone(err, res)
       }
@@ -125,4 +136,11 @@ class RpcEngine extends SafeEventEmitter {
   }
 }
 
+function serializeError(err) {
+  return {
+    code: err.code || -32603,
+    message: err.stack,
+  }
+}
+
 module.exports = RpcEngine

test/basic.spec.js

@@ -210,4 +210,30 @@ describe('basic tests', function () {
       done()
     })
   })
+
+  it('calls back next handler even if error', function (done) {
+    let engine = new RpcEngine()
+
+    let sawNextReturnHandlerCalled = false
+
+    engine.push(function (req, res, next, end) {
+      next(function (cb) {
+        sawNextReturnHandlerCalled = true
+        cb()
+      })
+    })
+
+    engine.push(function(req, res, next, end) {
+      end(new Error('boom'))
+    })
+
+    let payload = { id: 1, jsonrpc: '2.0', method: 'hello' }
+
+    engine.handle(payload, (err, res) => {
+      assert(err, 'did error')
+      assert(sawNextReturnHandlerCalled, 'saw next return handler called')
+      done()
+    })
+  })
+
 })