Fix: EmailReadImap unhandled promise rejection

[tennox]

EmailReadImap swallows errors & in log I see this (this issue is not about the errors, but error handling):

n8n_1  | (node:60) UnhandledPromiseRejectionWarning: Error: Unexpected search option: HEADER.CONTENT-TYPE "MULTIPART/MIXED"
n8n_1  |     ...
n8n_1  |     at ImapSimple.search (/usr/local/lib/node_modules/n8n/node_modules/imap-simple/lib/imapSimple.js:127:12)
n8n_1  |     at getNewEmails (/usr/local/lib/node_modules/n8n/node_modules/n8n-nodes-base/dist/nodes/EmailReadImap/EmailReadImap.node.js:219:46)
n8n_1  |     at Connection.onmail (/usr/local/lib/node_modules/n8n/node_modules/n8n-nodes-base/dist/nodes/EmailReadImap/EmailReadImap.node.js:344:50)
n8n_1  |     ...
n8n_1  | (node:60) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). To terminate the node process on unhandled promise rejection, use the CLI flag `--unhandled-rejections=strict` (see https://nodejs.org/api/cli.html#cli_unhandled_rejections_mode). (rejection id: 2)
n8n_1  | (node:60) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.
n8n_1  | (node:99) UnhandledPromiseRejectionWarning: NodeOperationError: Custom email config is not valid JSON.
n8n_1  |     at Connection.onmail (/usr/local/lib/node_modules/n8n/node_modules/n8n-nodes-base/dist/nodes/EmailReadImap/EmailReadImap.node.js:337:39)
n8n_1  |     ...
n8n_1  | (node:99) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). To terminate the node process on unhandled promise rejection, use the CLI flag `--unhandled-rejections=strict` (see https://nodejs.org/api/cli.html#cli_unhandled_rejections_mode). (rejection id: 1)
n8n_1  | (node:99) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

I have attempted to fix this by:

• config parsing: move outside the onmail handler (which means the thrown error should be catched normally)
• IMAP errors: emitting the error instead of throwing it

but:

• I did not manage to get my development environment to work (ERROR: LoggerProxy not initialized)
• I did not find documentation on how to correctly emit errors, so I did this:

  this.emit([[{
    json:{}, // seems like I have to pass it
    error: new NodeOperationError(this.getNode(), `IMAP query failed: ${error instanceof Error ? error.message : error}`)
  }]]);

Related to #2091 (but only partially)

[CLAassistant]

All committers have signed the CLA.

[krynble]

Hey @tennox

Thank you for your contribution. Sorry about the delay in getting back to you.

The first change you made, moving the parsing of the options upper makes total sense to me and helps you more easily find possible errors.

What worries me a bit is about the second change where the error property exists, but it will not cause the execution to display as an Error but as successful instead.

This property is meant for a future design and currently won't have the fully expected behavior, which is causing n8n to show this execution as an error.

I made some small changes and will be closing this PR in favor of https://github.com/n8n-io/n8n/pull/2991/files

[janober]

Thanks a lot for your contribution. Got merged with #2991

[janober]

Got released with n8n@0.169.0