Before adding "<defaultValue>" it was working but not now.

I tried

<constraint>
  <validator name="numeric" argument="--range 0-4294967295"/>
  <validator name="fqdn"/>
  <regex>(infinity)</regex>
</constraint>

2 validators also don't work.

I would have expected the output generated to be an OR of the validators or regexes and allow the output if any would have passed it

We can add a new <constraintGroup> element. If you put multiple <constraint> elements inside a <constraintGroup>, they work like logical AND.

If you have both <constraint> and <constraintGroup> elements under <properties>, a value must be valid for either that single constraint or the group.

This actually also happens for BGP which will confuse users

vyos@vyos# set protocols bgp 100 neighbor 1.1.1.1 remote-as internal
    'internal' is not a valid integer number

That would also good to get this working:

https://github.com/vyos/vyatta-cfg-quagga/blob/current/templates/policy/access-list6/node.def#L7-L12

Some notes from past meetings.

XML - current implementation:

<constraint>
  <validator name="numeric" argument="--range 1-65535"/>
</constraint>

XML - new implementation:

<constraint>
  .. validator node 1 ...
  <errorMessage>This is bad</errorMessage>
</constraint>
<constraint>
  .. validator node 2 ...
  <errorMessage>This is bad</errorMessage>
</constraint>

Only once <validator> should be supported per <constraint>

<constraintGroup>
  .. validator node 1 ...
  .. validator node 2 ...
  <errorMessage>This is bad</errorMessage>
</constraintGroup>

All constraints in <constraint> are run as logical OR, all validators under the <constraintGroup> node are run with a logical AND.

Having both constraint and constraintGroup will OR both together

Opening a new task for the issue described in the last comment, above. The original problem re. error messages was resolved in vyos-utils 68d1b283 .