Need clarification of docs/instrumenting/exposition_formats.md, is it missing information?

# HELP foo_total  
# TYPE foo_total counter
foo_total{hostname="localhost",optionalExtraMetadata="my-cool-value",} 1.0
# HELP foo_total  
# TYPE foo_total counter
foo_total{hostname="localhost",} 1.0

☝️ is this valid as of v0.4.0? I wrote an integration test that proves it is, but there is some debate on whether that's to spec or not.

Reading through https://github.com/prometheus/docs/blob/master/content/docs/instrumenting/exposition_formats.md

I am not seeing any reference to

A given metric name MAY NOT repeat if the cardinality of the label-value pairs between its instances varies.

From this section

of the legacy Client Data Exposition Format document.

Does this mean as of the current spec you can have the same metric more than once with varying labels?

Would be nice to add this info to the current doc.

Start with docs/instrumenting/exposition_formats.md, then compare its wording with the linked legacy Client Data Exposition Format document and review the linked integration test. Confirm whether repeated metric names with varying label sets are valid in the current specification; done means documenting the clarified rule in the current exposition-format documentation if warranted.