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 as separate read and write fields instead of combined entries. Readback operations explicitly use _RBV suffix PVs for clarity.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.22%. Comparing base (81f8fad) to head (454fb46).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #347      +/-   ##
==========================================
+ Coverage   91.21%   91.22%   +0.01%     
==========================================
  Files          70       70              
  Lines        2594     2599       +5     
==========================================
+ Hits         2366     2371       +5     
  Misses        228      228              

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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

Run ID: 6651aed6-35ba-4d2a-9462-75c337f2b298

📥 Commits

Reviewing files that changed from the base of the PR and between 81f8fad and 454fb46.

📒 Files selected for processing (2)

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

---

📝 Walkthrough

Walkthrough

The changes modify how read-write attributes are represented in the PVI structure. Instead of mapping a single "rw" field to a PV, the code now generates separate "r" and "w" fields pointing to the readback (_RBV) and write PVs respectively. Test expectations are updated to reflect this new structure.

Changes

Cohort / File(s)	Summary
PVI Structure Generation src/fastcs/transports/epics/pva/pvi.py	Modified _make_p4p_raw_value to split read-write attributes into separate read ("r") and write ("w") fields, with read fields pointing to _RBV suffixed PVs.
Test Schema Expectations tests/transports/epics/pva/test_p4p.py	Updated multiple test assertions to expect separate read/write field entries instead of combined "rw" entries across parent, child, and controller attribute tests.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Poem

🐰 RBV fields now split with care,
Read and write both standing there,
No more tangled paths to trace,
Each PV finds its proper place! ✨

🚥 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 summarizes the main change: adding separate 'r' and 'w' entries for AttrRW attributes in the PVI structure to address the readback (RBV) issue.
Linked Issues check	✅ Passed	The pull request fully implements the acceptance criteria from issue #346 by modifying the code to generate separate read ('r') and write ('w') entries for AttrRW attributes, with the 'r' entry pointing to the _RBV PV.
Out of Scope Changes check	✅ Passed	All changes are directly related to implementing the PVI structure fix for AttrRW attributes as specified in issue #346; no unrelated or out-of-scope modifications are present.

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✨ Finishing Touches

📝 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...