Form validation student project

Implement HTML5 form validation

Background information: The HTML5 specification defines a mechanism by which website authors can require browsers to validate the contents of forms before the user is allowed to submit them. Servo currently implements support for a subset of the form element types defined by the specification; this project is intended to implement the client-side validations steps and extend the supported subset to include additional form elements that support validation.

Initial steps:

• compile Servo and ensure that it runs on tests/html/about-mozilla.html
• email the mozilla.dev.servo mailing list (be sure to subscribe first!) introducing your group and asking any necessary questions
• uncomment the attributes in ValidityState.webidl and fix the resulting build errors by implementing appropriate stub methods in validitystate.rs
• make the ValidityState constructor take an &Element argument and store it as a JS<Element> member in ValidityState
• add a new bitflag type that represents each possible validity check in ValidityState
• define a Validatable trait that contains a method which accepts this bitflag as an argument (see the Activatable trait for inspiration)
• implement this trait for the form element types (HTMLInputElement, HTMLSelectElement, HTMLButtonElement, etc.), and define an as_maybe_validatable method on Element which returns an &Validatable value if the element implements the trait (see as_maybe_activatable for inspiration)
• Use the newly-added JS<Element> member to call these new methods as appropriate in each of the stub methods in ValidityState

Subsequent steps:

• Fill out HTMLFormElement::static_validation such that it implements the steps to statically validate the constraints of a form element
• Add reporting code to HTMLFormElement::interactive_validation that prints out problems with the form to the console using println!, and focus the first element that does not validate.
• Implement several validation states:
  • the minimum and maximum length constraints based on the minlength/maxlength members of HTMLInputElement
  • the missing constraint, using Element::has_attribute to determine if the required attribute is present
• Implement the checkValidity and reportValidity APIs for HTMLFormElement (see the guide for adding new methods based on web specifications)