Add g:formActionSubmit for client submission to multiple form urls

[jdaugherty]

As of HTML5, the input attribute formaction is the accepted way to submit to different URLs for a form on the client side with no javascript. This attribute is widely supported across all browsers:

I'd like to propose we adopt a tag formActionSubmit instead of implementing a server side solution via the tag actionSubmit (it uses a parameter with the format action_${actionName} to submit to different actions for the same controller).

[jdaugherty]

This change would have the added benefit of not relying on custom url mappings per the documentation here: https://gsp.grails.org/latest/ref/Tags/actionSubmit.html or default actions.

[codeconsole]

@jdaugherty perhaps you could provide more detail in this ticket description on how existing behavior works and how it will be changed. Specifically, how existing html is generated by the tag. I don't use this tag. It currently works by generating inline javascript?

[jdaugherty]

Prior to HTML5, an HTML form without any JavaScript could only submit to the URL specified in it's action attribute. Since it's useful to have a form submit to multiple actions depending on the button clicked, the actionSubmit tag was implemented so that the form action could have one URL and depending on a submitted parameter, Grails would call the desired action.

This allows for submitting multiple actions depending on the button clicked via server side code. It's implemented server side via DefaultUrlMappingInfo#checkDispatchAction in grails/grails-core. The button clicked will set a parameter with the prefix _action_ so the DefaultUrlMappingInfo knows to return a different action. This did not allow for calling another controller, only actions in the same controller as the form.

Given this example gsp template:

 <g:form name="testForm" controller="begin" action="update">
      <g:submitButton name="update" value="Call the update action" />
      <g:actionSubmit action="testAction" value="Call the other Test Action"/>
 </g:form>

This will generate the following HTML code:

 <form action="/begin/update" method="post" name="testForm" id="testForm" >
      <input type="submit" name="update" value="Call the update action" id="update" />
      <input type="submit" name="_action_testAction" value="Call the other Test Action" />
 </form>

When the user clicks on the button "Call the update action", the form will submit to /begin/update and on the server side the begin controller's action update will be called.

When the user clicks on the button "Call the other Test Action", the form will be submitted to /begin/update and the server will see the parameter _action_testAction. It will parse out the action of testAction and invoke that action instead of the update action on the begin controller.

Now that HTML5 has a valid way to invoke different URLs for a form, it makes sense to add a tag that supports the client side mechanism. I propose we deprecate the tag actionSubmit and if no major objections remove it in a future major release of Grails (post 7.0). It's possible there are implementations that rely on the _action_ prefix behavior. Deprecation would allow us to identify these cases as people update to later Grails versions and then decide if the legacy server side behavior should be maintained.

[jdaugherty]

An example project of the existing behavior is here: https://github.com/jdaugherty/grails-dual-action-submit-example

You can open the url http://localhost:8080/begin after starting this project to see this behavior.

[jdaugherty]

For this proposal, given this code:

 <g:form name="testForm" controller="begin" action="update">
      <g:submitButton name="update" value="Call the update action" />
      <g:formActionSubmit name="otherAction" action="testAction" value="Call the other Test Action"/>
 </g:form>

It would generate this html:

 <form action="/begin/update" method="post" name="testForm" id="testForm" >
      <input type="submit" name="update" value="Call the update action" id="update" />
      <input type="submit" formaction="/begin/testAction" name="otherAction" value="Call the other Test Action" />
 </form>

Clicking Call the update action would submit to /begin/update, clicking Call the other Test Action would submit to /begin/testAction

[codeconsole]

Ok, but won't you need a PR in grails-core deprecating the Url Mapping functionality?

[jdaugherty]

@codeconsole apache/grails-core#13905 will mark the grails-core code deprecated