On 2021-11-03, at 18:11, Mahesh Jethanandani <[email protected]> wrote:
> 
> I believe if you remove the anchor characters ^ and & from the pattern 
> statement, the default value will work.

Indeed.  And the reason is that YANG patterns are not PCRE/Javascript type 
regular expressions (which always require anchors unless used for searching), 
but W3C XSD type regular expressions, which are implicitly anchored.

https://www.rfc-editor.org/rfc/rfc7950.html#section-9.4.5

Most people learn about PCRE/Javascript type regular expressions first, which 
is a source of a common misunderstanding of YANG (and, CDDL, for that matter) 
regular expressions.

Grüße, Carsten

> 
>> On Nov 3, 2021, at 12:06 PM, Olumide <[email protected]> wrote:
>> 
[…]
>>            leaf wibble {
>>                type string {
>>                    pattern "^x$";
>>                }
>>                default "x";      ### NOT OKAY
>>            }
[…]
>> err : Value "x" does not satisfy the constraint "^x$" (range, length, or
>> pattern). (/tmp:wibble)
>> err : Module "tmp" parsing failed.
>> 
>> 
>> Regards,
>> 
>> - Olumide
>> 
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> 
> 

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