Re: [netmod] Fwd: Re: Leafref and require-instance=false

2015-06-08 Thread Andy Bierman 
On Mon, Jun 8, 2015 at 11:49 AM, Ladislav Lhotka lho...@nic.cz wrote:
 Andy Bierman a...@yumaworks.com writes:

 On Mon, Jun 8, 2015 at 8:39 AM, Kent Watsen kwat...@juniper.net wrote:



I think the two leafs are coupled through the path statement and so the
values of both should conform to the same type. If I extend Balazs¹
example with uint8 and 1..10 range:

1. Would a leafref value of 256 be acceptable?

2. How about foo?


 I agree it doesn't makes sense, but is the configuration invalid?

 The leafref is marked require-instance=false, it just means a matching
 condition will never succeed.


 If require-instance = false then the node must conform to
 the data type for the leaf.  This means the typedef used
 in the implemented version.

 Would a configuration be invalid if a when expression could never
 evaluate to true?


 The node would never appear in a configuration.
 A must-stmt then is always false would make the config invalid.

 What's actually relevant to the subject of this thread (and supports
 Kent's point somewhat) is this example:

 leaf foo {
   type uint8;
   must . = 10;
 }
 leaf bar {
   type leafref {
 require-instance false;
 path ../foo;
   }
 }

 Should bar20/bar be flagged as invalid? IMO no. At first sight it
 looks exactly like Balazs' example but in fact it is different - if
 there is no foo, the must expression doesn't apply.


I don't see where a range 1..20 is introduced.
The leaf bar has the same type as /foo,
so that is uint8.

I see your point... does require-instance false
mean it could be a valid value for the leaf, but
no instances happen to exist with that value?

Or does it mean valid for the same data-type but the instance
may never exist?

I think valid for the data type is correct.
The must-stmt says valid for the leaf to exist.
That is a separate test.

 Lada

Andy






 Kent



 Andy

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Re: [netmod] Fwd: Re: Leafref and require-instance=false

2015-06-08 Thread Martin Bjorklund 
Ladislav Lhotka lho...@nic.cz wrote:
 Andy Bierman a...@yumaworks.com writes:
 
  On Mon, Jun 8, 2015 at 8:39 AM, Kent Watsen kwat...@juniper.net wrote:
 
 
 
 I think the two leafs are coupled through the path statement and so the
 values of both should conform to the same type. If I extend Balazs¹
 example with uint8 and 1..10 range:
 
 1. Would a leafref value of 256 be acceptable?
 
 2. How about foo?
 
 
  I agree it doesn't makes sense, but is the configuration invalid?
 
  The leafref is marked require-instance=false, it just means a matching
  condition will never succeed.
 
 
  If require-instance = false then the node must conform to
  the data type for the leaf.  This means the typedef used
  in the implemented version.
 
  Would a configuration be invalid if a when expression could never
  evaluate to true?
 
 
  The node would never appear in a configuration.
  A must-stmt then is always false would make the config invalid.
 
 What's actually relevant to the subject of this thread (and supports
 Kent's point somewhat) is this example:
 
 leaf foo {
   type uint8;
   must . = 10;
 }
 leaf bar {
   type leafref {
 require-instance false;
 path ../foo;
   }
 }
 
 Should bar20/bar be flagged as invalid? IMO no.

No!  flagged as invalid is not precise enough - note that
foo20/foo is ok in some circumstances, e.g., it is ok to have
foo20/foo in the candidate.  However foo20/foo can never be
part of a valid configuration.

bar20/bar is always ok.


/martin

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Re: [netmod] Fwd: Re: Leafref and require-instance=false

2015-06-08 Thread Ladislav Lhotka 
Andy Bierman a...@yumaworks.com writes:

 On Mon, Jun 8, 2015 at 8:39 AM, Kent Watsen kwat...@juniper.net wrote:



I think the two leafs are coupled through the path statement and so the
values of both should conform to the same type. If I extend Balazs¹
example with uint8 and 1..10 range:

1. Would a leafref value of 256 be acceptable?

2. How about foo?


 I agree it doesn't makes sense, but is the configuration invalid?

 The leafref is marked require-instance=false, it just means a matching
 condition will never succeed.


 If require-instance = false then the node must conform to
 the data type for the leaf.  This means the typedef used
 in the implemented version.

 Would a configuration be invalid if a when expression could never
 evaluate to true?


 The node would never appear in a configuration.
 A must-stmt then is always false would make the config invalid.

What's actually relevant to the subject of this thread (and supports
Kent's point somewhat) is this example:

leaf foo {
  type uint8;
  must . = 10;
}
leaf bar {
  type leafref {
require-instance false;
path ../foo;
  }
}

Should bar20/bar be flagged as invalid? IMO no. At first sight it
looks exactly like Balazs' example but in fact it is different - if
there is no foo, the must expression doesn't apply.

Lada





 Kent



 Andy

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Re: [netmod] Fwd: Re: Leafref and require-instance=false

2015-06-08 Thread Kent Watsen 



I think the two leafs are coupled through the path statement and so the
values of both should conform to the same type. If I extend Balazs¹
example with uint8 and 1..10 range:

1. Would a leafref value of 256 be acceptable?

2. How about foo?


I agree it doesn't makes sense, but is the configuration invalid?

The leafref is marked require-instance=false, it just means a matching
condition will never succeed.

Would a configuration be invalid if a when expression could never
evaluate to true?


Kent

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Re: [netmod] Fwd: Re: Leafref and require-instance=false

2015-06-08 Thread Martin Bjorklund 
Andy Bierman a...@yumaworks.com wrote:
 On Mon, Jun 8, 2015 at 8:39 AM, Kent Watsen kwat...@juniper.net wrote:
 
 
 
 I think the two leafs are coupled through the path statement and so the
 values of both should conform to the same type. If I extend Balazs¹
 example with uint8 and 1..10 range:
 
 1. Would a leafref value of 256 be acceptable?
 
 2. How about foo?
 
 
  I agree it doesn't makes sense, but is the configuration invalid?
 
  The leafref is marked require-instance=false, it just means a matching
  condition will never succeed.
 
 
 If require-instance = false then the node must conform to
 the data type for the leaf.  This means the typedef used
 in the implemented version.

+1


/martin

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