fix: preserve empty array default value on JSONForm reset

[rasadregmi]

Summary

Fixes #41653. Resetting a JSON Form whose Array field defaults to [] created one empty array item, making the form invalid and unsubmittable. Reset now restores the empty default.

Root cause

schemaItemDefaultValue() in app/client/src/widgets/JSONFormWidget/helper.ts computes the array default as lodash.merge(processArray(...), sanitizedDefaultValue). processArray() always returns a single-item array because the __array_item__ schema entry always exists, and lodash.merge([item], []) keeps [item], so an empty default [] becomes [{}]. Form.onReset() (component/Form.tsx) feeds that value into reset(values, { keepErrors: true }), producing the phantom array item that fails required/regex validation.

Changes

• app/client/src/widgets/JSONFormWidget/helper.ts: return [] when the array schema item's defaultValue is an empty array
• app/client/src/widgets/JSONFormWidget/helper.test.ts: regression tests for both identifier and accessor key paths

Testing

• jest src/widgets/JSONFormWidget/helper.test.ts — 17/17 pass
• jest src/widgets/JSONFormWidget/fields/ArrayField.test.tsx — 2/2 pass
• tsc --noEmit — clean
• prettier --check and eslint on touched files — clean
• Verified the new tests fail without the fix

Closes #41653

Summary by CodeRabbit

• Bug Fixes

  • Empty array defaults in JSON forms are now preserved as empty arrays instead of being populated with unintended values.

• Tests

  • Added coverage for empty array defaults using both identifier- and accessor-based field configurations.

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• app/client/src/widgets/JSONFormWidget/helper.test.ts
• app/client/src/widgets/JSONFormWidget/helper.ts

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Walkthrough

The JSON Form helper now preserves empty array defaults instead of creating an empty array item. Tests cover both identifier and accessor key types.

Changes

JSON Form array default handling

Layer / File(s)	Summary
Preserve empty array defaults app/client/src/widgets/JSONFormWidget/helper.ts, app/client/src/widgets/JSONFormWidget/helper.test.ts	schemaItemDefaultValue returns [] immediately for empty array defaults. Tests cover identifier and accessor key types.

Priority: ⬆️ High

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

Change: Bug fix · Severity of issue fixed: High

Suggested reviewers: amelia-c0n

Merge Risk: ⚪ Minimal · up to e7cf5

The change correctly preserves empty array defaults during form resets, with coverage for both key paths. No merge-blocking risk remains.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely describes the primary change: preserving an empty array default when resetting a JSON Form.
Description check	✅ Passed	The description explains the issue, root cause, implementation, regression tests, validation results, and linked issue. It does not explicitly state dependencies or complete the Communication section,…
Linked Issues check	✅ Passed	Issue #41653 requires reset to preserve an Array field default of [] without creating an invalid item. In helper.ts, the ARRAY branch returns [] when schemaItem.defaultValue is an empty array,…
Out of Scope Changes check	✅ Passed	The changed files contain only the ARRAY default-value fix and regression tests for issue #41653. The changes support the linked issue and introduce no unrelated implementation or test scope.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 2…

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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_{Empty arrays stay still
Reset follows the default
No phantom rows bloom
Identifier and accessor agree
Validation rests calm}

_{Comment @coderabbitai help to get the list of available commands.}