fix(ui): Paste Chunk fills the destination's blanks instead of dropping structure (#589) [DO NOT MERGE — needs review]

[skearnes]

⚠️ Draft / do-not-merge. This changes Paste Chunk semantics on a shared, delicate code path. Per maintainer, it needs review from others before merging.

Summary

Per the maintainer decision on #589, Paste Chunk should "paste everything that isn't already set in the destination."

Today, paste applies only each entity's form-managed subset with a source-wins merge (deepMergeWithArrayMerge). Two consequences:

• A copied component's structure / identifiers are dropped on paste (they're excluded as sub-sidebar fields), so the target keeps its stale structure — the The Structure is not deleted when performing the Paste Chunk action for Components. #589 bug.
• Fields the destination already had get clobbered by the source.

New behavior — fillEmptyDeepMerge

A deep fill-empty merge:

• Keep every value the destination already has set; only fill its blanks from the chunk.
• Non-empty arrays are kept wholesale (we don't splice source items into a list the user already populated).
• Never paste separately-managed metadata — recordModified, automationCode, measurements (PASTE_PRESERVED_FIELDS) — preserving the fix(ui): submit filtered values on Paste Chunk (#601, #592) #704 fix even into a blank destination.
• The form still renders its managed subset, but we now persist the full merged entity, so pasted structure/identifiers the form itself doesn't show are saved.

"Not set" = nullish, empty string, or empty array/object. 0 and false count as set.

🔎 Key review questions

1. The PASTE_PRESERVED_FIELDS set (recordModified, automationCode, measurements) is the crux — it's what keeps fix(ui): submit filtered values on Paste Chunk (#601, #592) #704 from regressing. Is this the right/complete set of "never paste" fields across all entities (provenance, setup, product, conditions measurements, …)?
2. Behavior change for already-pasted fields: form fields (role, amount, source, …) now fill-empty instead of source-wins, so pasting onto a field the user already set keeps their value. Intended per "everything that isn't already set," but it's a change to existing paste behavior — please confirm.
3. Outcomes/Products follow the same path; confirm that's desired.

Test plan

• npx tsc -b clean
• npx vitest run — 561 passing; 10 new fillEmptyDeepMerge unit tests (fill-empty, preserve-set, nested, 0/false treated as set, never-paste metadata) + updated paste integration test (blank doi filled, recordModified not leaked).
• prettier / eslint clean
• Runtime verification in progress (driving copy/paste in the reaction editor); will attach findings as a comment. The structure-paste needs an external lookup / Ketcher to set up a structure, so the runtime check focuses on the observable fill-empty behavior on a plain field.

Closes #589.

🤖 Generated with Claude Code

[sonarqubecloud]

Quality Gate passed

Issues
1 New issue
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[codecov-commenter]

Codecov Report

❌ Patch coverage is 97.50000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 55.64%. Comparing base (167943c) to head (0f0840a).

Files with missing lines	Patch %	Lines
...ies/ReactionEntityForm/reactionEntityForm.utils.ts	96.66%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #725      +/-   ##
==========================================
+ Coverage   55.57%   55.64%   +0.07%     
==========================================
  Files         457      457              
  Lines       18355    18387      +32     
  Branches      742      753      +11     
==========================================
+ Hits        10200    10231      +31     
- Misses       8142     8143       +1     
  Partials       13       13              

Flag	Coverage Δ
python	83.69% <ø> (ø)
ui	51.39% <97.50%> (+0.09%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
...Entities/ReactionEntityForm/ReactionEntityForm.tsx	94.07% <100.00%> (+0.08%)	⬆️
...ies/ReactionEntityForm/reactionEntityForm.utils.ts	93.33% <96.66%> (+1.33%)	⬆️

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[skearnes]

Runtime verification note. I drove the no-auth stack to exercise this end-to-end in the reaction editor, but reliably automating the full path (add component A → set fields → Save → Copy Chunk → add component B → set one field → Paste Chunk → read back) kept fighting the editor's Drawer + "Reaction updated" toast + form-remount-on-save behavior. Rather than keep grinding browser automation, I'm relying on the deterministic coverage:

• fillEmptyDeepMerge unit tests (10): fill-empty, preserve a value the destination already set, keep an existing structure rather than replacing it, nested fill without clobbering, 0/false treated as set, and never-paste metadata (recordModified/automationCode/measurements) even into a blank destination.
• Paste integration test: confirms onPasteChunk submits the merged entity — blank doi filled from the chunk, the chunk's recordModified not leaked.

The editor flow is best exercised by a reviewer directly (the Key review questions in the description are the things to poke at). Happy to pair on a Playwright E2E for this once the semantics are agreed.

🤖 Generated with Claude Code