Handle Content-Type header for binary data in Response to Webhook node

[jburgers]

Hello,
I wanted to ask about a problem I faced during the development of a workflow. It seems to me that it is a bug, but as I am not completely sure that it is the expected behaviour I ask about it in this category.

Problem detected

I have a workflow that has a Webhook and after some processing the workflow ends generating a TSV file and returning it as binary data with content-type text/tab-separated-values

Below is the first approach I followed that didn’t work:

I expected that setting the content-type in the Respond to Webhook node should make the workflow return the content-type header with the text/tab-separated-values value. But these were the response headers:

Solution

I checked the source code of the Respond to Webhook node to know what was going on. And saw these lines in the case of binary response: n8n/RespondToWebhook.node.ts at master · n8n-io/n8n · GitHub

So I updated the workflow and set the mimeType in the Move Binary Data:

Now the response has the expected content-type:

Even when I set the content-type header in the Respond to Webhook node with the value any value. In fact, I have to set the header in that node even if I know it will be overwritten, because if I don’t set it the response will be without the content-type header.

So, here is my question:

Question

Is that the expected behaviour in case of a binary response in the Respond to Webhook node?

Or is a bug and those lines should be as the following?

if (!headers['content-type']) {
    headers['content-type'] = binaryData.mimeType;
}

For me makes more sense that if you set the content-type in the Respond to Webhook header is because you want that value. And only in case if you don’t set it, use the mimeType for the conent-type.

In case the current behaviour is the expected one, I would update the Respond to Webhook documentation page to add a warning to explain the behaviour of the content-type header in case the response type is binary.

Thanks in advance.

n8n setup

• n8n version: 0.209.4
• Database you’re using (default: SQLite): SQLite
• Running n8n with the execution process [own(default), main]: own
• Running n8n via [Docker, npm, n8n.cloud, desktop app]: Docker

[MutedJam]

Hi @jburgers, welcome to the community

This does look like a bug to me which I’ll add it to our engineering backlog for a fix.

It seems you have already figured out the workaround of setting the mime type on the Move Binary data node. Thanks so much for reporting this and please accept my apologies for the trouble this has caused.

[jburgers]

Hi @MutedJam,

Don’t worry about it. Thanks for the quick reply!

[jan]

Thanks a lot for making us aware of this issue. Got fixed and will be released with the next version:

fix(Respond to Webhook Node): Fix issue that content-type header gets overwritten

[jan]

Got released with [email protected]