Feature: Multi Page Form Support (port to 3.x)

[smg6511]

What does it do?

Note: This is a change that was merged into the develop branch (#259), but not carried over into the newer 3.x branch.

Changes how hasSubmission() is evaluated to allow multiple submit buttons to post the current form page (relevant in multi-step/page forms).

Why is it needed?

Multi step forms that span multiple pages are currently not possible and need a mechanism to persist data across pages.

Related issue(s)/PR(s)

There is a companion PR on the Formalicious repo (PR 18)

Example Form Template

To illustrate how this is set up, below is a template for a working form using the proposed feature. Note how the standard submitVar property is still used as it always has been, while additional buttons for navigating backward or to a specific step are appended with _[postfix].

<form action="[[!+currentUrl]]" id="form-[[!+id]]" method="post" enctype="multipart/form-data">
	<div class="grid-container fluid">
        <div class="grid-x grid-padding-x">
			[[!+step
				:lt=`[[+formaliciousSteps]]`
				:then=`<div class="form-step-navigation">[[!+formalicious.navigation]]</div>`
				:else=``
			]]

    		[[!+formalicious.form]]

			<div class="form-pagination">
			[[!+step
				:neq=`1`
				:then=`
					<button type="submit" class="button btn--prev" title="[[%formalicious.prev? &namespace=`formalicious` &topic=`default`]]" name="[[!+submitVar]]_prev" value="[[!+submitValPrev]]">
        		[[%formalicious.prev? &namespace=`formalicious` &topic=`default`]]
		    		</button>
				`
				:else=``
			]]
    				<button type="submit" class="button btn--next" name="[[!+submitVar]]"  title="[[!+submitTitle]]">
	        		[[!+submitTitle]]
	    			</button>
			[[!+step
				:lt=`[[+formaliciousSteps]]`
				:then=`
					<button type="submit" class="button btn--last" title="Skip to Last Step" name="[[!+submitVar]]_last" value="[[!+submitValLast]]">Skip to Last Step</button>
				`
				:else=``
			]]
			</div>
		</div>
	</div>
</form>