XPath expressions in 'when' statement not using the correct context

[eelcocramer]

I wanted to make this into a PR but cannot really find where this should be fixed. Any pointers that help me put this into a PR are appreciated!

I'm using the when statement in an action output:

output {
    leaf status {;
        type boolean;
        mandatory true;
    }
    leaf message {
        when "../status = 'false'";
        type string;
    }
}

According to yang linters the XPath ../status is correct but when I use this with freeconf I get an error in the restconf server's response: '..' not found in xpath

When I change the xpath query in the when statement to when "status = 'false'" the output of a restconf request is rendered correctly. However now the yang linters complain:

warning: node "component::status" is not found in "component::message"

[dhubler]

There's an xpath package and even a grammar file in yacc syntax that may or may not to the issue.

This is likely on the tougher side to look at, I can help if you cannot find it

On Sat, Jul 13, 2024, 5:20 AM Eelco @.***> wrote:

I wanted to make this into a PR but cannot really find where this should be fixed. Any pointers that help me put this into a PR are appreciated!

I'm using the when https://datatracker.ietf.org/doc/html/rfc7950#section-7.21.5 statement in an action output:

output { leaf status {; type boolean; mandatory true; } leaf message { when "../status = 'false'"; type string; } }

According to yang linters the XPath ../status is correct but when I use this with freeconf I get an error in the restconf servers response: '..' not found in xpath

When I change the xpath query in the when statement to when "status = 'false'" the output of a restconf request is rendered correctly. However now the yang linters complain:

warning: node "component::status" is not found in "component::message"

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[eelcocramer]

An update.

I added a test case to reproduce this issue in my cloned repository. Test case can be found here.

The error is generated in the resolvePath function of xpath_impl. It can easily be fixed by changing the behaviour of meta.Find but I have the feeling that is not the correct way to fix this issue. I do believe the selection where resolvePath is called with, is not the right selection.

[eelcocramer]

I tried running the test with a debugger to see if I could understand how it works but I'm lost at the yacc stuff.

[dhubler]

If the error is in resolvePath then bug is not in yacc.

Does the xpath work in config tree (i.e. not in an output directive)?

On Tue, Jul 16, 2024 at 3:18 AM Eelco @.***> wrote:

I tried running the test with a debugger to see if I could understand how it works but I'm lost at the yacc stuff.

— Reply to this email directly, view it on GitHub https://github.com/freeconf/yang/issues/112#issuecomment-2230193590, or unsubscribe https://github.com/notifications/unsubscribe-auth/AAACA7RKW5ZXYJ3HCH34Z4LZMTCLRAVCNFSM6AAAAABK2DYA3KVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZDEMZQGE4TGNJZGA . You are receiving this because you commented.Message ID: @.***>

[dhubler]

Is "../status" incorrect? parent of output would not have the "status" field.

[eelcocramer]

But ../status refers to the parent of message and that does have the status field. Without the ../ (so when this library does work) pyang and other linters complain with a warning that the node status is not found in the node message.