validation

I don’t try to re-implement full JSON Schema in Go, but I do like returning validation errors that are easy for clients to render. The pattern is: decode into a struct, validate required fields and invariants, and return a slice of {field, message} is

Hotwire forms feel “native” when invalid submissions keep you in context. Replace just the form frame with errors and keep the rest of the page intact. Return 422 so clients and caches behave correctly.

Async validation checks constraints that require server communication, like username availability or email uniqueness. React Hook Form's validate option accepts async functions that return error messages or true. I debounce async validators to avoid e

Query params arrive as strings, and ad-hoc parsing logic tends to drift across endpoints. I use Zod preprocessors to coerce values like page size and booleans, then validate the result. This keeps the handler readable and makes parsing rules shareable

I use clean_<fieldname>() to validate individual fields and clean() to validate field combinations. Raising ValidationError shows the message to the user near the appropriate field. For cross-field validation (like 'end date must be after start

Client-side validation provides instant feedback, but server-side validation is the source of truth. I use Stimulus to add real-time validations (format, length, required fields) while still rendering server errors when validations fail on submit. The