Form handling - binding, validation & render

[vim89]

Problem

Cask has no form handling utilities. Users must manually:

• Render forms with scalatags
• Parse form data
• Validate input (manual if-else chains)
• Display errors (manual)

// Current - everything manual
@cask.get("/users/new")
def newUser() = {
  import scalatags.Text.all._
  html(
    body(
      form(action := "/users", method := "post")(
        input(name := "name", `type` := "text"),
        input(name := "email", `type` := "email"),
        button("Create User")
      )
    )
  ).render
}

@cask.post("/users")
def create(name: String, email: String) = {
  // Manual validation
  if (name.isEmpty) cask.Abort(400, "Name required")
  if (!email.contains("@")) cask.Abort(400, "Invalid email")

  User.create(name, email)
  cask.Redirect("/users")
}

• Repetitive validation code
• No validation, form handling, error display

---

Solution

binding, simple validation, rendering with scalatags.

• form data binding to scalatags
• simple validations - throw Throwables
• Scalatags from functions

---

Questions -

• What form helpers are essential (text, email, password, select, etc.)?
• repopulation after errors?
• Multi-step forms
• No field-level error tracking

References

• scalatags for rendering
• uPickle for data binding

[lihaoyi]

I think this sounds reasonable. The key value here would be providing an integration between Scalatags for rendering, Cask for receiving the form fields, and uPickle for data-binding into a structured case class with optional validations. If you can bundle these nicely, that would make it much nicer to define simple interactive server-rendered websites