#8745 - Refactor: Use nullish coalescing operator

[bekaChaduneli]

How the feature works? / How did you fix the issue?

Replaced logical OR (||) operators with nullish coalescing (??) operators across all packages where the left-hand operand can only be null or undefined, following the @typescript-eslint/prefer-nullish-coalescing rule.

Changes made:

1. ketcher-macromolecules – editorSlice.ts, useIndigoVersionToRedux.ts - Replaced process.env.X || '' with ??

   • Before: process.env.BUILD_DATE || ''
   • After: process.env.BUILD_DATE ?? ''

2. ketcher-react – KetcherBuilder.ts - Replaced optional config params fallbacks

   • Before: buttons || {}, customButtons || [], process.env.VERSION || ''
   • After: buttons ?? {}, customButtons ?? [], process.env.VERSION ?? ''

3. ketcher-react – sgroup.ts, select.ts, rotate-controller.ts - Replaced editor.selection() || {} and ?.atoms || [] patterns

   • Before: this.editor.selection() || {}
   • After: this.editor.selection() ?? {}

4. ketcher-react – ContextMenu hooks (useAtomEdit, useBondEdit, useBondTypeChange, useChangeBondDirection, useRGroupAttachmentPointEdit, useRGroupAttachmentPointRemove) - Replaced optional prop fallbacks

   • Before: props?.bondIds || []
   • After: props?.bondIds ?? []

5. ketcher-react – Toolbar containers (TopToolbar, BottomToolbar, LeftToolbar, RightToolbar, FloatingTools) - Replaced Redux state fallbacks

   • Before: state.actionState || {}
   • After: state.actionState ?? {}

6. ketcher-core – Zoom.ts, BaseRenderer.ts, TransientDrawingView.ts - Replaced optional chained dimension fallbacks

   • Before: canvasWrapperBbox?.width || 0, ZoomTool.instance?.canvas || select(...)
   • After: canvasWrapperBbox?.width ?? 0, ZoomTool.instance?.canvas ?? select(...)

7. ketcher-core – remoteStructService.ts, SettingsManager.ts, rotate.ts, sgroup.ts, atom.ts, AttachmentPoint.ts - Replaced remaining optional-chain fallback patterns

8. ketcher-standalone – standaloneStructService.ts, indigoWorker.ts - Replaced selected || [] and options || {}

9. ketcher-macromolecules – rnaBuilderSlice.ts, librarySlice.ts, rnaBuilderSlice.helper.ts, manipulateCachedRnaPresets.ts, getMonomerName.ts, supportedFormatProperties.ts - Replaced label/preset/option fallbacks

Note: structConverter.ts was intentionally left unchanged — its || operators are boolean OR conditions in predicate logic (checking numeric 0-based flags), where replacing with ?? would change semantics and introduce bugs.

Approach: Only replaced || with ?? when:

• ✅ The left operand is typed as T | null | undefined
• ✅ The default value should only apply for null/undefined, not 0, false, or ""
• ✅ The replacement does not change runtime behavior

Check list

• unit-tests written
• e2e-tests written
• documentation updated
• PR name follows the pattern #1234 – issue name
• branch name doesn't contain '#'
• PR is linked with the issue
• base branch (master or release/xx) is correct
• task status changed to "Code review"
• reviewers are notified about the pull request