Refactor deviceAccess without semaphore using a simple queue

package.json

@@ -96,7 +96,6 @@
     "rxjs": "^6.2.1",
     "rxjs-compat": "^6.2.1",
     "secp256k1": "3.3.1",
-    "semaphore": "^1.1.0",
     "semver": "^5.5.0",
     "smoothscroll-polyfill": "^0.4.3",
     "source-map": "0.7.3",

src/helpers/deviceAccess.js

@@ -1,5 +1,4 @@
 // @flow
-import createSemaphore from 'semaphore'
 import type Transport from '@ledgerhq/hw-transport'
 import TransportNodeHid from '@ledgerhq/hw-transport-node-hid'
 import { DEBUG_DEVICE } from 'config/constants'
@@ -10,67 +9,34 @@ import { createCustomErrorClass } from './errors'
 // and guarantee we do one device access at a time. It also will handle the .close()
 // NOTE optim: in the future we can debounce the close & reuse the same transport instance.
 
-type WithDevice = (devicePath: string) => <T>(job: (Transport<*>) => Promise<T>) => Promise<T>
-
-const semaphorePerDevice = {}
+type WithDevice = (devicePath: string) => <T>(job: (Transport<*>) => Promise<*>) => Promise<T>
 
 const DisconnectedDevice = createCustomErrorClass('DisconnectedDevice')
 
-const remapError = <T>(p: Promise<T>): Promise<T> =>
-  p.catch(e => {
-    if (e && e.message && e.message.indexOf('HID') >= 0) {
-      throw new DisconnectedDevice(e.message)
-    }
-    throw e
-  })
+const mapError = e => {
+  if (e && e.message && e.message.indexOf('HID') >= 0) {
+    throw new DisconnectedDevice(e.message)
+  }
+  throw e
+}
 
-export const withDevice: WithDevice = devicePath => {
-  const sem =
-    semaphorePerDevice[devicePath] || (semaphorePerDevice[devicePath] = createSemaphore(1))
+let queue = Promise.resolve()
 
-  return job =>
-    takeSemaphorePromise(sem, devicePath, async () => {
-      const t = await retry(() => TransportNodeHid.open(devicePath), { maxRetry: 1 })
+export const withDevice: WithDevice = devicePath => job => {
+  const p = queue.then(async () => {
+    const t = await retry(() => TransportNodeHid.open(devicePath), { maxRetry: 1 })
+    if (DEBUG_DEVICE) {
+      t.setDebugMode(true)
+    }
+    try {
+      const res = await job(t).catch(mapError)
+      return res
+    } finally {
+      await t.close()
+    }
+  })
 
-      if (DEBUG_DEVICE) t.setDebugMode(true)
-      try {
-        const res = await remapError(job(t))
-        // $FlowFixMe
-        return res
-      } finally {
-        await t.close()
-      }
-    })
-}
+  queue = p.catch(() => null)
 
-function takeSemaphorePromise<T>(sem, devicePath, f: () => Promise<T>): Promise<T> {
-  return new Promise((resolve, reject) => {
-    sem.take(() => {
-      process.send({
-        type: 'setDeviceBusy',
-        busy: true,
-        devicePath,
-      })
-      f().then(
-        r => {
-          sem.leave()
-          resolve(r)
-          process.send({
-            type: 'setDeviceBusy',
-            busy: false,
-            devicePath,
-          })
-        },
-        e => {
-          sem.leave()
-          reject(e)
-          process.send({
-            type: 'setDeviceBusy',
-            busy: false,
-            devicePath,
-          })
-        },
-      )
-    })
-  })
+  return p
 }

yarn.lock

@@ -12810,10 +12810,6 @@ selfsigned@^1.9.1:
   dependencies:
     node-forge "0.7.5"
 
-semaphore@^1.1.0:
-  version "1.1.0"
-  resolved "https://registry.yarnpkg.com/semaphore/-/semaphore-1.1.0.tgz#aaad8b86b20fe8e9b32b16dc2ee682a8cd26a8aa"
-
 semver-diff@^2.0.0:
   version "2.1.0"
   resolved "https://registry.yarnpkg.com/semver-diff/-/semver-diff-2.1.0.tgz#4bbb8437c8d37e4b0cf1a68fd726ec6d645d6d36"