feat: support for omitzero added in Go 1.24

[perher]

This PR adds optional support for emitting omitzero tags (instead of omitempty). omitzero is a new feature that was added in Go 1.24 for json marshaling,

fixes #471

Summary by CodeRabbit

• New Features
  • Added a PreferOmitzero option so generated structs can use omitzero (Go 1.24+) instead of omitempty for JSON/YAML tags.
• Tests
  • Added tests and an example schema demonstrating omitzero generation and enforcing nullability checks during JSON/YAML deserialization.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
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Additional details and impacted files

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  Coverage        ?   41.44%           
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  Files           ?       67           
  Lines           ?     5801           
  Branches        ?        0           
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  Hits            ?     2404           
  Misses          ?     3118           
  Partials        ?      279           

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[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

Configuration used: defaults

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between b201caf and f15ccbd.

📒 Files selected for processing (5)

• pkg/generator/config.go
• pkg/generator/schema_generator.go
• tests/data/preferOmitzero/preferOmitzero.go
• tests/data/preferOmitzero/preferOmitzero.json
• tests/generation_test.go

🚧 Files skipped from review as they are similar to previous changes (5)

• tests/generation_test.go
• tests/data/preferOmitzero/preferOmitzero.go
• tests/data/preferOmitzero/preferOmitzero.json
• pkg/generator/config.go
• pkg/generator/schema_generator.go

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📝 Walkthrough

Walkthrough

Adds a PreferOmitzero boolean to generator config and updates the schema generator to emit ,omitzero instead of ,omitempty when set. Includes new test schema, generated types, and a test exercising the new flag.

Changes

Cohort / File(s)	Summary
Config & Generator pkg/generator/config.go, pkg/generator/schema_generator.go	Added PreferOmitzero bool to Config. Generator now uses ,omitzero for JSON tags when the flag is true; existing required/omitempty disabling logic preserved.
Test data & generated types tests/data/preferOmitzero/preferOmitzero.json, tests/data/preferOmitzero/preferOmitzero.go	Added JSON schema and generated Go file demonstrating omitzero tags, with custom UnmarshalJSON/UnmarshalYAML that validate null constraints for specific fields.
Tests tests/generation_test.go	Added TestPreferOmitzero which enables PreferOmitzero on a config copy and runs generation tests against the new dataset.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~12 minutes

Poem

🐰 I wiggle a flag and say hello,
omitzero hops where omitempty used to go.
Slices stay put, not vanished from view,
Tests crunch carrots to prove that's true.
A tiny rabbit smiles — code fresh and new.

🚥 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 and specifically describes the main feature: adding support for omitzero, a Go 1.24 feature.
Linked Issues check	✅ Passed	Changes implement omitzero support across config, schema generation, and test fixtures, meeting the core objective of supporting Go 1.24's omitzero tag for JSON marshaling.
Out of Scope Changes check	✅ Passed	All changes directly support the omitzero feature: configuration field, generation logic, test schema, and test case. No unrelated modifications detected.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment

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[coderabbitai]

Actionable comments posted: 1

🤖 Fix all issues with AI agents

In `@pkg/generator/config.go`:
- Around line 38-39: Fix the typo in the comment for the PreferOmitzero field:
change the phrase "will use omit omitzero" to "will use omitzero" in the comment
above the PreferOmitzero bool declaration so the comment reads that
PreferOmitzero will use omitzero instead of omitempty (requires Go 1.24+);
update the comment attached to PreferOmitzero accordingly.

🧹 Nitpick comments (2)

tests/data/preferOmitzero/preferOmitzero.go (2)

46-66: Note: Unused raw variable in generated code.

The raw map is unmarshalled but never used (lines 47-50). This appears to be a pre-existing pattern in the generator templates, likely used for other validation scenarios. Consider cleaning up the generator template to omit this when not needed, but this is outside the scope of this PR.

---

68-89: Same observation for UnmarshalYAML.

The raw map decoding (lines 70-73) follows the same unused pattern as UnmarshalJSON. Same suggestion applies regarding generator template cleanup as a future improvement.