Feature Request: Support for Embedded Structs in Query Parameters

[Lenstack]

Problem

Encore doesn't recognize embedded structs when parsing query parameters or generating API docs, forcing developers to duplicate common fields across every endpoint.

What doesn't work:

// shared/pagination.go
type PageRequest struct {
    Page  int `query:"page"`
    Limit int `query:"limit"`
}

// customer/dto.go
type GetCustomersRequest struct {
    shared.PageRequest  // ❌ NOT recognized - fields ignored
}

Result: page and limit don't appear in docs and aren't parsed.

Current workaround (requires duplication):

type GetCustomersRequest struct {
    Page  int `query:"page"`   // ✅ Must copy-paste in every endpoint
    Limit int `query:"limit"`  // ✅ Must copy-paste in every endpoint
}

Expected Behavior

Encore should process embedded struct fields with query: tags just like Go's standard library does:

type GetCustomersRequest struct {
    shared.PageRequest           // Should work - fields inherited
    Search string `query:"search"`
}

type GetProductsRequest struct {
    shared.PageRequest              // Reuse across all endpoints
    Category string `query:"category"`
}

All fields (including embedded) should:

• Parse from HTTP requests
• Appear in generated documentation
• Work in API explorer

Impact

Without this feature:

• 20 paginated endpoints = 40 lines of duplicated code
• Changes to pagination require updating 20+ files
• Easy to create inconsistencies

With this feature:

• Define once, reuse everywhere
• Changes propagate automatically
• Standard Go composition patterns work as expected

Use Cases

Common reusable patterns that need this:

• Pagination (PageRequest)
• Filtering (FilterRequest)
• Sorting (SortRequest)
• Multi-tenant parameters
• Audit metadata

Technical Note

Go's encoding/json and reflection properly handle embedded structs. Encore's compile-time code generation should do the same by recursively traversing embedded fields when analyzing request structs.

---

This limitation breaks Go's composition idioms and forces non-idiomatic workarounds. Supporting embedded structs would align Encore with Go conventions and significantly reduce boilerplate.