Better document error handling in hooks

Environment (please complete the following information):

• WebdriverIO version: [e.g. 4.13.2]
• Mode: testrunner
• If WDIO Testrunner, running sync/async: sync & async
• Node.js version: 12
• Browser name and version: Chrome 85
• Platform name and version: Windows 10

Describe the bug I was having trouble with some tests when I realized, that my onPrepare hook was throwing an error. The test still ran as usual but since my backend wasn’t running, I was getting misleading errors.

To Reproduce Add this hook to your config.

onPrepare: async function (config, capabilities) {
      throw new Error("error")
}

// or 

onPrepare: function (config, capabilities) {
      throw new Error("error")
}

Log

...
2020-09-25T10:57:13.724Z ERROR @wdio/cli:utils: Error in hook: Error: error
    at Object.onPrepare (C:\Development\anvajo datalab\test\config\wdio.conf.ts:251:13)
    at C:\Development\anvajo datalab\node_modules\@wdio\cli\build\utils.js:95:14
    at Array.map (<anonymous>)
    at runLauncherHook (C:\Development\anvajo datalab\node_modules\@wdio\cli\build\utils.js:93:27)
    at Launcher.run (C:\Development\anvajo datalab\node_modules\@wdio\cli\build\launcher.js:78:41)
    at processTicksAndRejections (internal/process/task_queues.js:97:5)
Starting ChromeDriver 85.0.4183.87 (cd6713ebf92fa1cacc0f1a598df280093af0c5d7-refs/branch-heads/4183@{#1689}) on port 9515
...

Expected behavior An error in onPrepare hook should abort the test.

[christian-bromann]

FYI: the solution to use SevereServiceError in TypeScript and WebdriverIO sync mode is by using require to avoid type clashings.

const { SevereServiceError } = require('webdriverio')

[christian-bromann]

it shouldn’t if you explicitly set @wdio/sync types:

    "types": [
      "node",
      "@wdio/mocha-framework",
      "@wdio/sync"
    ],