Module flash 

Leaving something for the next request from the same visitor.

A form that fails validation has to answer twice over: tell the person what is wrong, and give them back what they typed. Neither can travel in the response, because the answer to a failed POST is a redirect — sending the page directly would leave the browser on a URL that re-submits the form when reloaded, which is the double-charge problem in miniature.

So the errors and the old input are left where the next request will find them, and the browser is sent back to the form.

The trait is here rather than in rustlavel-auth on purpose. Validation needs somewhere to leave errors and must not therefore depend on sessions; the view layer needs to read them and must not depend on either. A session registers itself as Arc<dyn Flash> on the request, and everything else talks to that.

Constants

ERRORS_KEY

The key a failed validation leaves its messages under.

OLD_INPUT_KEY

The key it leaves the submitted input under.

PREVIOUS_URL_KEY

The key the session middleware records the last page under, so a failed form knows where “back” is.

Traits

Flash

Somewhere a value can be left for exactly one further request.

Functions

is_local_path

Whether a redirect target is a path on this site rather than another origin.

old_input_of

The submitted fields worth keeping, as a JSON object.