Mandatory field not honoured at the time of validation

[KBA07]

Consider a yang file:
`
module file {
yang-version 1.1;
namespace "urn:config:yang:interfaces";
prefix "dns-config";

import ietf-inet-types {
	prefix inet;
}
// import ietf-yang-types {
// 	prefix yang;
// }

organization	"ABC";

description	"YANG module for DNS configuration";

revision 2021-03-03 {
	description "Initial version";
}

container dnsconfig {
	leaf DNSFwdSelection {
		type string {
			length "1";
			pattern "[0-3]";
		}
		default "0";
	}
	leaf rdodhcpserver {
		type string {
			length "1";
			pattern "[0-3]";
		}
		default "0";
	}
	leaf dns1 {
		type inet:ipv4-address;
		mandatory true;
	}
}

}
`

When I validate this Yang file using go yang, I get the output below:
`
(ENV) IN-GN-53202:config_managment kashif.ali$ ./bin/goyang src/file.yang
2021/04/05 12:17:03 Registering default
2021/04/05 12:17:03 Registering default

// YANG module for DNS configuration
rw: dns-config:file {
rw: dns-config:dnsconfig {
rw: string dns-config:DNSFwdSelection
rw: ipv4-address dns-config:dns1
rw: string dns-config:rdodhcpserver
}
}
`

Now I used this file to generate a GO Struct using the Ygot package. I use that generated file to unmarshal the incoming JSON data against the generated GO struct, now when I validate that struct, in case if the dns1 field is missing. The validation doesn't throw any error as such for mandatory field missing.

Is there anything am I missing or is this the desired behavior?
In case if this is desired, then how do we enforce mandatory field at the time of validation?

Also when I validate the same yang file using pyang, I get a clear indication of which fields are mandatory(Highlighted in bold below). However, This is not the case with goyang.
(ENV) IN-GN-53202:config_managment kashif.ali$ pyang src/file.yang -f tree module: file +--rw dnsconfig +--rw DNSFwdSelection? string +--rw rdodhcpserver? string **+--rw dns1 inet:ipv4-address**

[robshakir]

Today, ygot doesn't have support for validating whether a mandatory field is populated. This is something that could be added, and we'd be happy to help with a design/pull request for doing so if you'd like to collaborate on one.

Thanks,
r.

[KBA07]

@robshakir I would love to collaborate, but is there any documentation or such which covers the code organization or flow. That would be helpful for me to fix this issue.

Thanks,
Kashif Ali