fix: correct error span attributes for Datadog error tracking

[wewelll]

Summary

• Fix error.type extraction by changing tag to _tag property check to correctly handle Effect TaggedError
• Wrap Cause.squashWith calls in String() to ensure span attributes are always strings
• This ensures error.type, error.message, and error.stack are properly set for Datadog error tracking

Problem

When a handler in a subscriber returned an error, the onFailure handler was not correctly setting the error.type and error.stack span attributes for Datadog. Only error.message was being set.

The root cause was that the code checked for a tag property, but Effect TaggedError uses _tag as the property name.

Changes

• packages/amqp/src/AMQPSubscriber.ts
• packages/nats/src/JetStreamSubscriber.ts
• packages/nats/src/NATSSubscriber.ts

[Copilot]

Pull request overview

This PR fixes error span attributes for Datadog error tracking by correcting the property check for Effect's TaggedError and ensuring span attributes are always strings.

Changes:

• Changed property check from tag to _tag to correctly extract error type from Effect TaggedError
• Wrapped Cause.squashWith calls in String() to ensure span attributes are always strings
• Updated error handling in AMQP and NATS subscribers

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
packages/nats/src/NATSSubscriber.ts	Fixed error.type extraction and wrapped error attributes in String()
packages/nats/src/JetStreamSubscriber.ts	Fixed error.type extraction and wrapped error attributes in String()
packages/amqp/src/AMQPSubscriber.ts	Fixed error.type extraction and wrapped error attributes in String()
.changeset/fix-error-span-attributes.md	Added changeset documentation for the fix

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[thibautsa]

Nice thanks @wewelll !