share operator

[btilds]

Adds share() as a shortcut for the multicast<Subject>() | ref_count() pipeline. It is templated over the subject with publish_subject as the default, mirroring multicast(), so share<some_subject>() works too.

Because it composes the existing template_multicast_t and ref_count(), the resulting observable type is identical to what publish() | ref_count() produces today, making it a drop-in replacement at existing call sites.

Covered by a new share test case in test_connectable_observable.cpp and a doxygen sample.

Summary by CodeRabbit

• New Features

  • Added a share operator for multicasting observable values across multiple subscribers.
  • Automatically connects on the first subscription and disconnects after the last subscriber unsubscribes.
  • Supports configurable subject types, with publish behavior by default.
  • Added usage documentation and examples.

• Tests

  • Added coverage for shared subscriptions, lazy connections, subscriber lifetimes, and reconnection behavior.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro Plus

Run ID: 9062dfa6-d2cb-46ad-8fc6-d9d24cb8d361

📥 Commits

Reviewing files that changed from the base of the PR and between d54535d and d9eda58.

📒 Files selected for processing (5)

• src/examples/rpp/doxygen/share.cpp
• src/rpp/rpp/operators.hpp
• src/rpp/rpp/operators/fwd.hpp
• src/rpp/rpp/operators/share.hpp
• src/tests/rpp/test_connectable_observable.cpp

Included review availability: Your plan includes up to 2 reviews per rolling hour; 1 remains after this review.

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📝 Walkthrough

Walkthrough

The pull request adds a configurable share operator. It combines multicast behavior with reference counting, includes tests for subscription lifecycle behavior, and adds a Doxygen example.

Changes

Share operator

Layer / File(s)	Summary
Share API and implementation src/rpp/rpp/operators/fwd.hpp, src/rpp/rpp/operators/share.hpp, src/rpp/rpp/operators.hpp	The public share API uses publish_subject by default and implements sharing through multicast and ref_count.
Share subscription behavior tests src/tests/rpp/test_connectable_observable.cpp	Tests cover lazy subscription, one shared source subscription, observer-specific unsubscription, completion, and reconnection.
Executable documentation example src/examples/rpp/doxygen/share.cpp	The example demonstrates two observers receiving values from a shared observable.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Merge Risk:⚪ Minimal · up to d9eda

This PR adds a localized share() convenience operator with accompanying tests and documentation; no actionable merge-blocking risk remains beyond normal checks and review.

Sequence Diagram(s)

sequenceDiagram
participant ObserverA
participant ObserverB
participant ShareOperator
participant Source
ObserverA->>ShareOperator: subscribe
ShareOperator->>Source: subscribe on first observer
ObserverB->>ShareOperator: subscribe
Source-->>ShareOperator: emit value
ShareOperator-->>ObserverA: deliver value
ShareOperator-->>ObserverB: deliver value
ObserverA-->>ShareOperator: unsubscribe
ObserverB-->>ShareOperator: remain subscribed
ObserverB-->>ShareOperator: unsubscribe
ShareOperator->>Source: dispose after last observer

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Suggested reviewers:alexinlog

Poem

A rabbit shares one stream of cheer,
Two listeners hop and gather near.
One source subscription starts the show,
Each receives the values that flow.
When all hop off, the stream lets go.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely identifies the main change: adding the share operator.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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