Escalate errors on RPC responses

README.md

@@ -75,3 +75,6 @@ engine.push(function(req, res, next, end){
   end(new Error())
 })
 ```
+
+That said, `next()` will detect errors on the RPC response, and cause
+`end(res.error)` to be called.

package.json

@@ -1,6 +1,6 @@
 {
   "name": "json-rpc-engine",
-  "version": "5.1.2",
+  "version": "5.1.3",
   "description": "a tool for processing JSON RPC",
   "license": "ISC",
   "author": "kumavis",
@@ -20,7 +20,7 @@
   },
   "dependencies": {
     "async": "^2.0.1",
-    "eth-json-rpc-errors": "^0.3.1",
+    "eth-json-rpc-errors": "^1.0.1",
     "promise-to-callback": "^1.0.0",
     "safe-event-emitter": "^1.0.1"
   },

src/index.d.ts

@@ -1,5 +1,5 @@
 
-import { IJsonRpcError } from 'eth-json-rpc-errors'
+import { IJsonRpcError } from 'eth-json-rpc-errors/@types'
 
 /** A String specifying the version of the JSON-RPC protocol. MUST be exactly "2.0". */
 export type JsonRpcVersion = "2.0";

src/index.js

@@ -97,16 +97,22 @@ class RpcEngine extends SafeEventEmitter {
       middleware(req, res, next, end)
 
       function next (returnHandler) {
-        // add return handler
-        allReturnHandlers.push(returnHandler)
-        cb()
+        if (res.error) {
+          end(res.error)
+        } else {
+          // add return handler
+          allReturnHandlers.push(returnHandler)
+          cb()
+        }
       }
 
       function end (err) {
         // if errored, set the error but dont pass to callback
-        if (err) {
-          res.error = serializeError(err)
-          res._originalError = err
+        const _err = err || (res && res.error)
+        // const _err = err
+        if (_err) {
+          res.error = serializeError(_err)
+          res._originalError = _err
         }
         // mark as completed
         isComplete = true
@@ -120,6 +126,8 @@ class RpcEngine extends SafeEventEmitter {
       if (err) {
         // prepare error message
         res.error = serializeError(err)
+        // remove result if present
+        delete res.result
         // return error-first and res with err
         return onDone(err, res)
       }

test/basic.spec.js

@@ -84,7 +84,7 @@ describe('basic tests', function () {
     })
   })
 
-  it('erroring middleware test', function (done) {
+  it('erroring middleware test: end(error)', function (done) {
     let engine = new RpcEngine()
 
     engine.push(function (req, res, next, end) {
@@ -97,6 +97,45 @@ describe('basic tests', function () {
       assert(err, 'did error')
       assert(res, 'does have response')
       assert(res.error, 'does have error on response')
+      assert(!res.result, 'does not have result on response')
+      done()
+    })
+  })
+
+  it('erroring middleware test: res.error -> next()', function (done) {
+    let engine = new RpcEngine()
+
+    engine.push(function (req, res, next, end) {
+      res.error = new Error('no bueno')
+      next()
+    })
+
+    let payload = { id: 1, jsonrpc: '2.0', method: 'hello' }
+
+    engine.handle(payload, function (err, res) {
+      assert(err, 'did error')
+      assert(res, 'does have response')
+      assert(res.error, 'does have error on response')
+      assert(!res.result, 'does not have result on response')
+      done()
+    })
+  })
+
+  it('erroring middleware test: res.error -> end()', function (done) {
+    let engine = new RpcEngine()
+
+    engine.push(function (req, res, next, end) {
+      res.error = new Error('no bueno')
+      end()
+    })
+
+    let payload = { id: 1, jsonrpc: '2.0', method: 'hello' }
+
+    engine.handle(payload, function (err, res) {
+      assert(err, 'did error')
+      assert(res, 'does have response')
+      assert(res.error, 'does have error on response')
+      assert(!res.result, 'does not have result on response')
       done()
     })
   })