fix: add 'r' and 'w' entries for AttrRWs

[shihab-dls]

closes #346

Amends PVI structure, such that we get:

structure a
  string r P4P_TEST_DEVICE:A_RBV
  string w P4P_TEST_DEVICE:A

Summary by CodeRabbit

• Enhancements
  • Improved attribute access handling in EPICS PVA transport: read-write attributes now expose separate read and write fields.
  • Readback operations explicitly use _RBV suffix PVs for clearer value reporting.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.42%. Comparing base (a2e77b6) to head (4451d14).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #347      +/-   ##
==========================================
+ Coverage   91.41%   91.42%   +0.01%     
==========================================
  Files          72       72              
  Lines        2935     2940       +5     
==========================================
+ Hits         2683     2688       +5     
  Misses        252      252              

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[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 7f09f932-9442-459b-80cb-d75b88a2e464

📥 Commits

Reviewing files that changed from the base of the PR and between 454fb46 and 4451d14.

📒 Files selected for processing (2)

• src/fastcs/transports/epics/pva/pvi.py
• tests/transports/epics/pva/test_p4p.py

🚧 Files skipped from review as they are similar to previous changes (2)

• tests/transports/epics/pva/test_p4p.py
• src/fastcs/transports/epics/pva/pvi.py

---

📝 Walkthrough

Walkthrough

The changes update PVI structures for read-write attributes. They now expose separate "r" readback fields using _RBV PVs and "w" write fields. Tests update expectations for parent, child, and controller attributes.

Changes

PVI read/write mapping

Layer / File(s)	Summary
Split read-write attribute mappings src/fastcs/transports/epics/pva/pvi.py	_make_p4p_raw_value maps "rw" attributes to separate "r" readback and "w" write entries. Other access modes retain direct mappings.
Update PVI schema expectations tests/transports/epics/pva/test_p4p.py	Tests expect separate readback and write entries for parent, child, and controller attributes. The vector mapping formatting changes without changing its value.

Estimated code review effort: 2 (Simple) | ~10 minutes

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly describes the main change: adding separate read and write entries for AttrRW attributes.
Linked Issues check	✅ Passed	The implementation maps AttrRW reads to the _RBV PV and writes to the write PV, and tests verify separate r and w entries required by #346.
Out of Scope Changes check	✅ Passed	The changes are limited to AttrRW PVI mapping and corresponding test expectations, with no unrelated code changes.

✨ Finishing Touches 💡 1

📝 Generate docstrings 💡

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch amend_pvi_structure

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[coretl]

Hmm, this means we would have both a read and write table. We should discuss this...

[coretl]

Decided on a different tack:

• FastCS always makes separate R and W PVs
• We exposure them in the UI in the most compact way possible

This might mean some Phoebus level construct that merges the 2 PVs into one widget, or 2 buttons that launch the 2 widgets