From ce2834400ca202d5767c3d896407ac565fadfc14 Mon Sep 17 00:00:00 2001
From: bitpshr <mail@bitpshr.net>
Date: Mon, 14 May 2018 08:33:47 -0400
Subject: Add new json-rpc-engine middleware for improved error handling

---
 app/scripts/lib/createErrorMiddleware.js | 66 ++++++++++++++++++++++++++++++++
 app/scripts/lib/inpage-provider.js       |  2 +
 2 files changed, 68 insertions(+)
 create mode 100644 app/scripts/lib/createErrorMiddleware.js

(limited to 'app/scripts/lib')

diff --git a/app/scripts/lib/createErrorMiddleware.js b/app/scripts/lib/createErrorMiddleware.js
new file mode 100644
index 000000000..baed99e45
--- /dev/null
+++ b/app/scripts/lib/createErrorMiddleware.js
@@ -0,0 +1,66 @@
+const log = require('loglevel')
+
+/**
+ * JSON-RPC error object
+ *
+ * @typedef {Object} RpcError
+ * @property {number} code - Indicates the error type that occurred
+ * @property {Object} [data] - Contains additional information about the error
+ * @property {string} [message] - Short description of the error
+ */
+
+/**
+ * Middleware configuration object
+ *
+ * @typedef {Object} MiddlewareConfig
+ * @property {boolean} [override] - Use RPC_ERRORS message in place of provider message
+ */
+
+/**
+ * Map of standard and non-standard RPC error codes to messages
+ */
+const RPC_ERRORS = {
+  1: 'An unauthorized action was attempted.',
+  2: 'A disallowed action was attempted.',
+  3: 'An execution error occurred.',
+  [-32600]: 'The JSON sent is not a valid Request object.',
+  [-32601]: 'The method does not exist / is not available.',
+  [-32602]: 'Invalid method parameter(s).',
+  [-32603]: 'Internal JSON-RPC error.',
+  [-32700]: 'Invalid JSON was received by the server. An error occurred on the server while parsing the JSON text.',
+  internal: 'Internal server error.',
+  unknown: 'Unknown JSON-RPC error.',
+}
+
+/**
+ * Modifies a JSON-RPC error object in-place to add a human-readable message,
+ * optionally overriding any provider-supplied message
+ *
+ * @param {RpcError} error - JSON-RPC error object
+ * @param {boolean} override - Use RPC_ERRORS message in place of provider message
+ */
+function sanitizeRPCError (error, override) {
+  if (error.message && !override) { return error }
+  const message = error.code > -31099 && error.code < -32100 ? RPC_ERRORS.internal : RPC_ERRORS[error.code]
+  error.message = message || RPC_ERRORS.unknown
+}
+
+/**
+ * json-rpc-engine middleware that both logs standard and non-standard error
+ * messages and ends middleware stack traversal if an error is encountered
+ *
+ * @param {MiddlewareConfig} [config={override:true}] - Middleware configuration
+ * @returns {Function} json-rpc-engine middleware function
+ */
+function createErrorMiddleware ({ override = true } = {}) {
+  return (req, res, next) => {
+    next(done => {
+      const { error } = res
+      if (!error) { return done() }
+      sanitizeRPCError(error)
+      log.error(`MetaMask - RPC Error: ${error.message}`, error)
+    })
+  }
+}
+
+module.exports = createErrorMiddleware
\ No newline at end of file
diff --git a/app/scripts/lib/inpage-provider.js b/app/scripts/lib/inpage-provider.js
index 99cc5d2cf..4e65f0a23 100644
--- a/app/scripts/lib/inpage-provider.js
+++ b/app/scripts/lib/inpage-provider.js
@@ -1,5 +1,6 @@
 const pump = require('pump')
 const RpcEngine = require('json-rpc-engine')
+const createErrorMiddleware = require('./createErrorMiddleware')
 const createIdRemapMiddleware = require('json-rpc-engine/src/idRemapMiddleware')
 const createStreamMiddleware = require('json-rpc-middleware-stream')
 const LocalStorageStore = require('obs-store')
@@ -44,6 +45,7 @@ function MetamaskInpageProvider (connectionStream) {
   // handle sendAsync requests via dapp-side rpc engine
   const rpcEngine = new RpcEngine()
   rpcEngine.push(createIdRemapMiddleware())
+  rpcEngine.push(createErrorMiddleware())
   rpcEngine.push(streamMiddleware)
   self.rpcEngine = rpcEngine
 }
-- 
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