XPath to check if control value valid - orbeon

Question

Is there a way to check if a control value is valid (a value is present if required and the value is valid)? I have tried using xf:valid and xxf:valid, but none work as I expected (seem to have to change another, unrelated control for it to redo the calculate value.
2016.2 form builder example form - email-valid value correct once change value of control-5.
<xh:html xmlns:xh="http://www.w3.org/1999/xhtml" xmlns:xf="http://www.w3.org/2002/xforms"
xmlns:xs="http://www.w3.org/2001/XMLSchema"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:ev="http://www.w3.org/2001/xml-events"
xmlns:xi="http://www.w3.org/2001/XInclude"
xmlns:xxi="http://orbeon.org/oxf/xml/xinclude"
xmlns:xxf="http://orbeon.org/oxf/xml/xforms"
xmlns:exf="http://www.exforms.org/exf/1-0"
xmlns:fr="http://orbeon.org/oxf/xml/form-runner"
xmlns:saxon="http://saxon.sf.net/"
xmlns:sql="http://orbeon.org/oxf/xml/sql"
xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/"
xmlns:fb="http://orbeon.org/oxf/xml/form-builder">
<xh:head>
<xh:title>Untitled Form</xh:title>
<xf:model id="fr-form-model" xxf:expose-xpath-types="true">
<!-- Main instance -->
<xf:instance id="fr-form-instance" xxf:exclude-result-prefixes="#all" xxf:index="id">
<form>
<section-1>
<email-required/>
<email/>
<email-valid/>
<control-5/>
</section-1>
</form>
</xf:instance>
<!-- Bindings -->
<xf:bind id="fr-form-binds" ref="instance('fr-form-instance')">
<xf:bind id="section-1-bind" name="section-1" ref="section-1">
<xf:bind id="email-required-bind" name="email-required" ref="email-required"
xxf:whitespace="trim"/>
<xf:bind id="email-bind" ref="email" name="email" type="xf:email" xxf:whitespace="trim"
required="//email-required ne ''"/>
<xf:bind id="email-valid-bind" ref="email-valid" name="email-valid"
calculate="if (xxf:valid(//email)) then 'good' else 'bad'"/>
<xf:bind id="control-5-bind" ref="control-5" name="control-5" xxf:whitespace="trim"/>
</xf:bind>
</xf:bind>
<!-- Metadata -->
<xf:instance xxf:readonly="true" id="fr-form-metadata" xxf:exclude-result-prefixes="#all">
<metadata>
<application-name>TEST</application-name>
<form-name>TEST</form-name>
<title xml:lang="en">Untitled Form</title>
<description xml:lang="en"/>
</metadata>
</xf:instance>
<!-- Attachments -->
<xf:instance id="fr-form-attachments" xxf:exclude-result-prefixes="#all">
<attachments>
<css mediatype="text/css" filename="" size=""/>
<pdf mediatype="application/pdf" filename="" size=""/>
</attachments>
</xf:instance>
<!-- All form resources -->
<xf:instance xxf:readonly="true" id="fr-form-resources" xxf:exclude-result-prefixes="#all">
<resources>
<resource xml:lang="en">
<section-1>
<label>Untitled Section</label>
</section-1>
<email-required>
<label>Email Required?</label>
<hint/>
</email-required>
<email>
<label>Emal</label>
<hint/>
</email>
<email-valid>
<label>Email Valid</label>
<hint/>
</email-valid>
<control-5>
<label>Random Field</label>
<hint/>
</control-5>
</resource>
</resources>
</xf:instance>
<!-- Utility instances for services -->
<xf:instance id="fr-service-request-instance" xxf:exclude-result-prefixes="#all">
<request/>
</xf:instance>
<xf:instance id="fr-service-response-instance" xxf:exclude-result-prefixes="#all">
<response/>
</xf:instance>
</xf:model>
</xh:head>
<xh:body>
<fr:view>
<fr:body xmlns:xbl="http://www.w3.org/ns/xbl" xmlns:p="http://www.orbeon.com/oxf/pipeline"
xmlns:oxf="http://www.orbeon.com/oxf/processors">
<fr:section id="section-1-control" bind="section-1-bind">
<xf:label ref="$form-resources/section-1/label"/>
<fr:grid>
<xh:tr>
<xh:td>
<xf:input id="email-required-control" bind="email-required-bind">
<xf:label ref="$form-resources/email-required/label"/>
<xf:hint ref="$form-resources/email-required/hint"/>
<xf:alert ref="$fr-resources/detail/labels/alert"/>
</xf:input>
</xh:td>
<xh:td>
<xf:input id="email-control" bind="email-bind">
<xf:label ref="$form-resources/email/label"/>
<xf:hint ref="$form-resources/email/hint"/>
<xf:alert ref="$fr-resources/detail/labels/alert"/>
</xf:input>
</xh:td>
</xh:tr>
<xh:tr>
<xh:td>
<xf:output id="email-valid-control" bind="email-valid-bind">
<xf:label ref="$form-resources/email-valid/label"/>
<xf:hint ref="$form-resources/email-valid/hint"/>
<xf:alert ref="$fr-resources/detail/labels/alert"/>
</xf:output>
</xh:td>
<xh:td>
<xf:input id="control-5-control" bind="control-5-bind">
<xf:label ref="$form-resources/control-5/label"/>
<xf:hint ref="$form-resources/control-5/hint"/>
<xf:alert ref="$fr-resources/detail/labels/alert"/>
</xf:input>
</xh:td>
</xh:tr>
</fr:grid>
</fr:section>
</fr:body>
</fr:view>
</xh:body>
</xh:html>

Answer 1

The reason this happens is the processing model in XForms:
First, data is updated and recalculated.
Second, data is revalidated.
So if you make a calculation dependent on validation, you can get into the kind of cycle you are seeing, namely that things don't happen in the order you expect. This could, possibly, be fixed by a more subtle dependency algorithm (see also this RFE), but currently this is how things must happen.
In these situations, you could use actions, something like:
<xf:setvalue
observer="email-valid-control"
event="xforms-valid"
ref="bind('email-valid-bind')"
value="true()"/>
<xf:setvalue
observer="email-valid-control"
event="xforms-invalid"
ref="bind('email-valid-bind')"
value="false()"/>
This is heavier, and requires you to use custom model logic, but it's the only reliable way right now.