expositionformats.internal is imported by exposition-textformats but exported by nothing, breaking OSGi resolution #2395

Summary

In 1.8.0, prometheus-metrics-exposition-textformats imports io.prometheus.metrics.expositionformats.internal, but no artifact exports it. The classes exist in prometheus-metrics-exposition-formats, which keeps them unexported, so the two bundles cannot be wired together and any OSGi container fails to resolve io.prometheus.metrics.expositionformats.

Evidence

From the published 1.8.0 manifests:

prometheus-metrics-exposition-textformats-1.8.0.jar
  Export-Package: io.prometheus.metrics.expositionformats
  Import-Package: io.prometheus.metrics.expositionformats.internal      <- nothing provides this

prometheus-metrics-exposition-formats-1.8.0.jar
  Export-Package: io.prometheus.metrics.expositionformats.generated
                  io.prometheus.metrics.expositionformats.generated.com_google_protobuf_4_35_0
  Import-Package: io.prometheus.metrics.expositionformats

The implementation classes are in the second jar but not exported from it:

$ unzip -l prometheus-metrics-exposition-formats-1.8.0.jar | grep expositionformats/internal
  io/prometheus/metrics/expositionformats/internal/PrometheusProtobufWriterImpl.class
  io/prometheus/metrics/expositionformats/internal/ProtobufUtil.class

prometheus-metrics-exposition-textformats-1.8.0.jar contains none of them, so the import is not satisfiable from within its own bundle either.

How I hit it

Micrometer has an OSGi test that is still pinned to the old simpleclient because of an earlier failure (micrometer-metrics/micrometer#5063). Switching it to the current client, the bnd resolution now stops here:

micrometer-osgi-test-tests cannot be resolved
  ⇒ Import-Package io.micrometer.prometheusmetrics could not be provided
    ⇒ Import-Package io.prometheus.metrics.expositionformats;version=[1.8.0,2.0.0) could not be provided
      ⇒ Import-Package io.prometheus.metrics.expositionformats.internal could not be provided

The blocker reported back in 2024 (the shaded protobuf module not being a bundle) is gone, this is what is left.

Possible fixes

Either export io.prometheus.metrics.expositionformats.internal from prometheus-metrics-exposition-formats, or move the two classes so the package does not have to cross a bundle boundary. The first is a one line manifest change but does publish an internal package; the second is cleaner if you would rather not.

I saw #989 was closed as not planned, though that was about prometheus-metrics-shaded-protobuf, which no longer exists in 1.8.0. This one is a metadata inconsistency between two shipped artifacts rather than a request for OSGi support, so I thought it was worth reporting separately. Happy to send a PR for whichever direction you prefer.

Environment

• io.prometheus:* 1.8.0
• bnd resolution via Micrometer's micrometer-osgi-test (Felix framework)