oss_16_baggage_metadata_and_percent_encoding

[ocelotl]

Closes #20

Preserve W3C Baggage entry metadata and percent-encode spaces as %20 (Linear OSS-16, findings P2/P3). set_baggage gains optional metadata + get_baggage_metadata; propagator splits/re-appends metadata and uses quote/unquote. Validation: api suite 45 passed (baggage+w3c propagator), scope api+changelog. Note: 3 pre-existing tests that asserted the old buggy behavior were updated.

Linear issue: https://linear.app/dash0/issue/OSS-16/p2-p3-w3c-baggage-metadata-dropped-wrong-percent-encoding-vs-percent20

[ocelotl]

🔒 Internal (dash0) — not for upstream.

• Linear: https://linear.app/dash0/issue/OSS-16/p2-p3-w3c-baggage-metadata-dropped-wrong-percent-encoding-vs-percent20 (findings P2/P3)
• Closes: oss_16_baggage_metadata_and_percent_encoding #20 · Branch: oss_16_baggage_metadata_and_percent_encoding · Commit: c35142d9e
• Validation: api suite 45 passed; scope api + changelog. 3 pre-existing tests that asserted the old buggy behavior were updated.

[ocelotl]

📣 Public-facing draft — to be used for the upstream PR in open-telemetry/opentelemetry-python. No internal references; copy verbatim.

Title: Preserve W3C Baggage metadata and fix space percent-encoding

What

Fixes two W3C Baggage conformance issues in opentelemetry-api:

1. Preserve entry metadata. set_baggage accepts an optional metadata: str | None, a new get_baggage_metadata(name, context=None) accessor is added, and W3CBaggagePropagator splits an entry's value from its ;-delimited metadata on extract, stores the metadata, and re-appends it verbatim on inject. Metadata is kept in a separate Context entry, so get_baggage/get_all still return plain string values.
2. Correct space encoding. Inject/extract use urllib.parse.quote(..., safe="") / unquote instead of quote_plus/unquote_plus, so a space is %20 (per the W3C Baggage format / RFC 3986). safe="" preserves the previous /-escaping.

Why

Metadata was validated then discarded and there was no API to set it, so properties were silently lost (cf. Go baggage.Property, Java BaggageEntryMetadata). quote_plus emitted spaces as +, which compliant receivers misinterpret; the spec requires %20.

Spec

W3C Baggage format: https://www.w3.org/TR/baggage/ · OpenTelemetry Baggage API: specification/baggage/api.md

Tests

New: metadata round-trips extract→inject; metadata via set_baggage is re-appended; no metadata leaves none; overwriting/removing/clearing drops metadata; space injects as %20 and extracts back. Updated 3 pre-existing tests that asserted the old behavior. Full opentelemetry-api suite: 288 passed, 1 skipped.

Backward compatibility

set_baggage(name, value[, context]) unchanged; metadata is a new optional keyword; get_baggage/get_all still return plain values.