Help! My Velocity {{my.token}} previews correctly, but I can’t approve the email

Velocity is already verbose, but you’ve still gotta code defensively even if that means a little more code.

Crucially, in the Marketo-Velocity ecosystem, don’t assume code will only run in the context of a Person record. Prepare for person fields and object lists to be empty. This is true, for example, during asset approval.

Take this little snippet that adds a footer including the email domain:

#set( $emailParts = $lead.Email.split("@") )
#set( $emailDomain = $emailParts[1] )
If this email was mistakenly routed to your spam folder, ask the administrator of the ${emailDomain} mailserver to allow future emails from info@example.com. 

It’ll run fine when you preview by a Person or List, but when you try to approve you’ll get:

You can’t see the full error in the popup, but if you look at the underlying Java error it’s an ArrayIndexOutOfBoundsException.[1]

And this makes sense! On line 1 the (overly naïve) email parser does a split() on @, then on line 2 it assumes the resulting array has at least 2 items.

This assumption is true of any valid email address. But when you approve, the placeholder value in $lead.Email, as with all Person fields checked off in Script Editor, is an empty string. You can split() an empty string, no problem. But the array only has 1 item (also an empty string). So if you try to seek the 2nd item — index [1] since arrays are 0-based — that’s out of bounds.

While Velocity swallows a lot of errors that would be fatal in pure Java, this isn’t one of them. Exceeding the length of an array is always fatal.

Coding for Approve Email

Simplest defensive move is checking if $lead.Email is empty before continuing. This will let you approve the asset:

#if( !$lead.Email.isEmpty() )
#set( $emailParts = $lead.Email.split("@") )
If this email was mistakenly routed to your spam folder, ask the administrator of the ${emailDomain} mailserver to allow future emails from info@example.com.
#end

The above assumes $lead.email is either empty or valid. A valid address must have an @ sign, so it doesn’t check beyond that.

If you want to also cover people with an invalid — but non-empty – $lead.Email, switch it around so you split() and check the expected length:

#set( $emailParts = $lead.Email.split("@") )
#if( $emailParts.size() > 1 )
#set( $emailDomain = $emailParts[1] )
If this email was mistakenly routed to your spam folder, ask the administrator of the ${emailDomain} mailserver to allow future emails from info@example.com.
#end

Even better, rethink split-and-get-2nd-item. As noted above, this is a naïve way of parsing the domain out of an email address.[2] Don’t you really mean split-and-get-last-item? I think you do. So if you do that, no matter whether $lead.email is empty, valid, or invalid, there’s no error:

#set( $emailParts = $lead.Email.split("@") )
#set( $emailDomain = $emailParts[$math.sub($emailParts.size(),1)] )
If this email was mistakenly routed to your spam folder, ask the administrator of the ${emailDomain} mailserver to allow future emails from info@example.com. 

Notes

[1] In a local Velocity environment you see the stack trace:

Error invoking method 'get(java.lang.Integer)' in [Ljava.lang.String; at dynmacro.vm[line 52, column 33]
        at org.apache.velocity.runtime.parser.node.ASTIndex.execute(ASTIndex.java:175)
        at org.apache.velocity.runtime.parser.node.ASTReference.execute(ASTReference.java:280)
        at org.apache.velocity.runtime.parser.node.ASTReference.value(ASTReference.java:567)
        at org.apache.velocity.runtime.parser.node.ASTExpression.value(ASTExpression.java:71)
        at org.apache.velocity.runtime.parser.node.ASTSetDirective.render(ASTSetDirective.java:142)
        at org.apache.velocity.runtime.parser.node.SimpleNode.render(SimpleNode.java:342)
        at org.apache.velocity.Template.merge(Template.java:356)
        at org.apache.velocity.Template.merge(Template.java:260)
        at VTLRunner.main(VTLRunner.java:92)
Caused by: java.lang.reflect.InvocationTargetException
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
        at java.lang.reflect.Method.invoke(Method.java:597)
        at org.apache.velocity.util.introspection.UberspectImpl$VelMethodImpl.doInvoke(UberspectImpl.java:395)
        at org.apache.velocity.util.introspection.UberspectImpl$VelMethodImpl.invoke(UberspectImpl.java:384)
        at org.apache.velocity.runtime.parser.node.ASTIndex.execute(ASTIndex.java:149)
        ... 8 more
Caused by: java.lang.ArrayIndexOutOfBoundsException
        at java.lang.reflect.Array.get(Native Method)
        at org.apache.velocity.util.ArrayListWrapper.get(ArrayListWrapper.java:43)

[2] It’s wrong for old-school but valid syntax like "sandy@home"@example.com.