[SalesForce] How to make a custom label display ‘nothing’

I did this a very different way...

So rather than use a Formula field to do this I use a workflow rule with a field update. The amount of space in the field update is much greater so your statements will not be an issue.

In fact I use this method to check the difference between the Product total amount (roll up of Opportunity Line Item) and the Estimated Revenue that the Opportunity Owner enters manually (this being their best idea of the value of the opportunity at any given step).

We check the month, quarter and year of the opportunity, check whether the value is above or below a certain threshold and the line of business and the end response sets a field (called RedAmberGreen__c) that is not on their page view and then I use a formula field to show either a red, amber or green light.

It simply means:

1. When you have a label attribute, the component level error message would show error in context label passed in attribute.
2. When your have a empty label attribute or does not have a label attribute at all, it would not show any message with the default field's label.

Difficult to understand; maybe it would be clear when you try the example.

Output on click of save when email is empty (code at the end)-

Note: Error message for second and third sections/input are same (as apex:pageMessage doesn’t show duplicate message), default message with field's label; only difference is in #3 we have empty label hence it doesn't show a field label because its expecting us to add.

Code for illustration:

<apex:page standardController="Contact">
    <apex:form id="form">
        <apex:pageMessages></apex:pageMessages>
        <apex:pageBlock title="Quick Edit: {!Contact.Name}">
            <apex:pageBlockSection title="1. Dynamic Label" columns="1">
                <apex:inputText value="{!Contact.Email}" 
                    label="{!Contact.FirstName + '’s Email'}" required="true"/>
            </apex:pageBlockSection>
            <apex:pageBlockSection title="2. No label" columns="1">
                <apex:inputText value="{!Contact.Email}" required="true"/>
            </apex:pageBlockSection>
            <apex:pageBlockSection title="3. Empty label" columns="1">
                <apex:inputText value="{!Contact.Email}" label="" required="true"/>
            </apex:pageBlockSection>
            <apex:pageBlockSection title="4. From custom Label" columns="1">
                <apex:inputText value="{!Contact.Email}" 
                    label="{!$Label.Label_Contact_Email}" required="true"/>
            </apex:pageBlockSection>
            <apex:pageBlockButtons >
                <apex:commandButton action="{!save}" value="Save" rerender="form"/>
            </apex:pageBlockButtons>
        </apex:pageBlock>
    </apex:form>
</apex:page>