Span.addLink throws when using @vercel/otel due to missing method

[nicole0707]

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N/A

Link to the code that reproduces this issue. A link to a public Github Repository or gist with a minimal reproduction.

https://github.com/nicole0707/otel-addlink-compat-repro

A step-by-step description of how to reproduce the issue, based on the linked reproduction.

• npm install
• npm start

A clear and concise description of what the bug is, and what you expected to happen.

When using @vercel/otel for OpenTelemetry initialization, spans do not support the .addLink() method.

In the PubsubSpans.createPublishRpcSpan() and similar methods, addLink is called unguarded. However, Vercel’s OTEL wrapper currently uses @opentelemetry/api@1.0.0, which does not support addLink() on the span object.

This leads to runtime errors:

TypeError: span.addLink is not a function

Expected behavior:

The library should check whether .addLink is supported before calling it.

This would allow compatibility with OTEL wrappers like @vercel/otel, even if they’re on older SDK versions.

A clear and concise description WHY you expect this behavior, i.e., was it a recent change, there is documentation that points to this behavior, etc. **

The OpenTelemetry spec introduced Span.addLink() more recently, and not all implementations support it yet, particularly lightweight wrappers like Vercel’s.

[nicole0707]

@feywind Could you please take a look when you have a moment? We've unable to upgrade the latest npm package due to the issue that breaks the application.

[feywind]

@nicole0707 Sorry for the delay. I suspect the answer might be "we only support newer official OTel libraries" but I'll ask around.

[nicole0707]

@feywind Thanks for the context, it makes sense. Still, it probably shouldn't break the app. Would you mind having a quick look at the fix? #2061 🙏

[feywind]

Coming back to revisit this... the more I stare at it, the less it makes sense to me to check for the method existing. The official typings don't list it as optional for Span:

addLink(link: Link): this;

I do get that OTel play a bit fast and loose with their interface compatibility :| but it's also not really tenable for us to have to check the existence of each method during version updates.

Has @vercel/otel updated by now?

[feywind]

Closing for lack of response, comment/reopen if still needed.