fix: Make copyWith parameters nullable

[tilucasoli]

Related issue

Fixes an issue where copyWith method parameters were not always optional, which could cause compilation errors when non-nullable types were used.

Description

The code generator now ensures all copyWith parameters are nullable (optional), regardless of whether the original field type is nullable or not. This is the expected behavior for copyWith methods, where you only provide the values you want to change.

Changes

• spec_mixin_builder.dart: Modified copyWith parameter generation to append ? to types that are not already nullable
• spec_mixin_builder_test.dart: Added comprehensive unit tests covering:
  • Nullable and non-nullable fields
  • Mixed type scenarios
  • Complex types (e.g., BoxDecoration, AlignmentGeometry)
  • List types
  • Null-coalescing usage in the copyWith body
  • Prevention of double ?? suffix

Review Checklist

• Testing: Have you tested your changes, including unit tests and integration tests for affected code?
• Breaking Changes: Does this change introduce breaking changes affecting existing code or users?
• Documentation Updates: Are all relevant documentation files (e.g. README, API docs) updated to reflect the changes in this PR?
• Website Updates: Is the website containing the updates you make on documentation?

Additional Information (optional)

This fix ensures that generated copyWith methods follow Dart's idiomatic pattern where all parameters are optional. For example:

// Before (broken for non-nullable types):
TestSpec copyWith({
  String name,  // Required because non-nullable
})

// After (correct):
TestSpec copyWith({
  String? name,  // Optional, uses ?? this.name fallback
})

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Project	Deployment	Actions	Updated (UTC)
mix-docs	Ready	Preview, Comment	Feb 6, 2026 1:41am