Slack Trigger node throws errors on `File Shared` event

[krzysztof-pyrzyk-ah]

Bug Description

Slack Trigger node throws erros when listening on File Shared event:

TypeError: Cannot read properties of undefined (reading 'channel') at WebhookContext.webhook (/usr/local/lib/node_modules/n8n/node_modules/n8n-nodes-base/dist/nodes/Slack/SlackTrigger.node.js:299:76) at Workflow.runWebhook (/usr/local/lib/node_modules/n8n/node_modules/n8n-workflow/dist/Workflow.js:660:38) at Object.executeWebhook (/usr/local/lib/node_modules/n8n/dist/webhooks/webhook-helpers.js:144:48) at processTicksAndRejections (node:internal/process/task_queues:95:5) at /usr/local/lib/node_modules/n8n/dist/webhooks/test-webhooks.js:101:37.

This trigger fails on files of any type or size.

Slack App Event Subscription and Scopes are configured properly.

To Reproduce

1. Configure Slack App with all recommended scopes and Event Subscription on file sharing event.
2. Add Slack Trigger node to a workflow and make it listen on file sharing.
3. Tets the trigger.
4. Post file on Slack.
5. See described error.

Expected behavior

Uploaded file is being captured by the treigger propery and is available as an output from the node.

Operating System

Oracle Linux 9

n8n Version

1.69.2

Node.js Version

20.18.0

Database

SQLite (default)

Execution mode

main (default)

[Joffcom]

Hey @krzysztof-pyrzyk-ah,

We have created an internal ticket to look into this which we will be tracking as "GHC-541"

[DeepakJaiz]

Hey @Joffcom Is this resolved? I am getting same error.

[andreygargul]

Getting the same error

[wanshot]

Is there an alternative here?

[esjewett]

This is happening because the file_share event uses the channel_id attribute and the existing trigger code doesn't handle it. I've posted about this here: https://community.n8n.io/t/slack-trigger-throwing-error-on-audio-file-create/92364/3

I am unable to build n8n, so can't test this out, but something like this diff should fix the problem if anyone is up for testing it locally and creating a pull request:

--- a/packages/nodes-base/nodes/Slack/SlackTrigger.node.ts
+++ b/packages/nodes-base/nodes/Slack/SlackTrigger.node.ts
@@ -343,7 +343,10 @@ export class SlackTrigger implements INodeType {
                }
 
                if (eventType !== 'team_join') {
-                       eventChannel = req.body.event.channel ?? req.body.event.item.channel;
+                       eventChannel =
+                               req.body.event.channel ??
+                               req.body.event.item?.channel ??
+                               req.body.event.channel_id;
 
                        // Check for single channel
                        if (!watchWorkspace) {

[sfc-gh-puneet-lakhanpal]

I can validate that the slack trigger is successful if the above change happens as suggested by @esjewett . I built n8n locally using the above change and validated.

[josediaz1208]

Getting the same error. Also noticed its inconsistent sometimes it works and other times it does not.

[igdr]

the same error, version [email protected]

[sfc-gh-puneet-lakhanpal]

I was able to fix the error and use it in my local environment. However, it was a long process. Can we please fix this ?

Here's what i did on my end to get this working -

Fork the n8n repo and git clone it to your local. On mac: set it up like this: brew install node@22 echo 'export PATH="/opt/homebrew/opt/node@22/bin:$PATH"' >> /Users/<USERNAME>/.zshrc brew install corepack corepack enable corepack prepare pnpm --activate conda create -n n8n python=3.10 conda activate n8n pip install setuptools echo "python=/opt/anaconda3/envs/n8n/bin/python" >> .npmrc pnpm install

I made the change as documented here - https://github.com/n8n-io/n8n/issues/11994#issuecomment-2846344075

then built a new docker image like below: Modified the line number 11 and 12 in docker/images/n8n/Dockerfile as below: ENV NODE_OPTIONS='--max-old-space-size=16384' RUN pnpm build || (echo "Build failed, retrying with more debugging" && NODE_OPTIONS='--max-old-space-size=16384' pnpm build)

Then run docker build --platform linux/amd64 -t n8ncustom -f docker/images/n8n/Dockerfile .

and then use the FROM docker.io/library/n8ncustom:latest to create whatever docker container you need

[falzfalzfalz]

Cmon guys this such an easy fix please follow up on this @Joffcom

[JohnYeung-dojjy]

I tried to implement automatic invoice processing by allowing user to upload their invoices onto slack. This is a blocking factor.

[Chesars]

Hi! I was able to reproduce this issue in my local environment and got the same error "Cannot read properties of undefined (reading 'channel')" at first. Then I applied the code changes suggested by @esjewett, build, tested again in a production mode, and it worked perfectly. I’m going to open a PR to fix this problem for Slack users who want to use this functionality in n8n. Hope this helps!