Support type discrimination for nested sum types with integer and number variants

[lanej]

Problem

Currently, type-based discrimination is disabled for nested sum types that contain both integer and number variants (gen/schema_gen_sum.go:197-201):

if hasInteger && hasNumber && hasSumVariant {
    // TODO(tdakkota): Do not allow type discriminator for nested sum types with integer and
    // 	number variants at the same time. We can add support for this later, but it's not trivial.
    return false
}

This limitation means that schemas with nested oneOf/anyOf containing both integer and number types will fail type discrimination and fall back to other discrimination methods.

Example Scenario

oneOf:
  - type: integer
  - type: number
  - oneOf:  # nested sum type
      - type: string
      - type: boolean

This would be rejected for type discrimination even though the outer types (integer, number, nested-sum) are distinguishable.

Why This Limitation Exists

The challenge is that at JSON runtime level:

• Both integer and number map to jx.Number
• When a nested sum type also needs to discriminate between integer/number internally, the discrimination logic becomes complex
• The current implementation doesn't handle the multi-level type checking required

Proposed Solution

To lift this limitation, we would need to:

1. Enhanced type tracking: Track not just the outer JSON type but also the nested discrimination strategy
2. Nested validation: When encountering jx.Number, check if the value is an integer (no decimal part) vs float
3. Cascading discrimination: If outer type matches, cascade to inner sum type's discrimination logic

Implementation Complexity

This is marked as "not trivial" because:

• Requires runtime integer vs float detection (value == math.Floor(value) or similar)
• Template generation becomes more complex (nested switches)
• Need to handle validation errors at multiple levels
• Performance implications of additional type checking

Related

• PR feat(gen): add type-based oneOf/anyOf discrimination #1584: Type-based oneOf/anyOf discrimination
• gen/schema_gen_sum.go: canUseTypeDiscriminator function