KafkaJS.Consumer: subscribe({ topics: [/someRegex$/] }) unexpected behavior

[justjake]

Environment Information

• OS [e.g. Mac, Arch, Windows 10]: macOS 14.5 (23F79)
• Node Version [e.g. 8.2.1]: v18.17.0
• NPM Version [e.g. 5.4.2]: 9.6.7
• C++ Toolchain [e.g. Visual Studio, llvm, g++]: Xcode 14
• confluent-kafka-javascript version [e.g. 2.3.3]: "@confluentinc/kafka-javascript": "0.1.16-devel"

Steps to Reproduce

When subscribing to topics via a regex, a start-of-string anchor is silently prepended to the regex:

consumer.subscribe({ topics: [/someSuffix$/ })

This is equivalent to:

consumer.subscribe({ topics: [/^someSuffix$/ })

This happens because the underlying rdkafka library only recognizes regex subscriptions if the start with a ^ character. Instead of silently prepending a ^, I would expect the KafkaJS client behavior to either:

• Throw an error if the regex provided doesn't start with ^, so the developer understands the constraint and can adjust their code accordingly
• Preprend ^.*, to ensure we match all topics that matched the user's input regex of /someSuffix$/, as /^.*someSuffix$/.

[milindl]

Yep, that makes sense, I'll throw an error and add it to the migration guide, because we definitely don't want to trip people up without warning.

[milindl]

I made the change to remedy this, it'll be present in the next release.

[milindl]

Closing with release 0.1.17-devel