How to refine the mandatory property of nodes from a grouping in YANG language?

Question

I defined a grouping which has a leaf with mandatory property set to false. But in some cases, I would like to use this grouping and specify that the leaf should be mandatory. How do I achieve this in YANG?

Answer 1

You would use the refine statement when specifying a use of your grouping.

module mandatory-and-grouping {
  namespace "org:example:mandatory-and-grouping";
  prefix "mag";

  grouping my-grouping {
    leaf my-leaf {
      type string;
    }
  }

  container top {
    uses my-grouping {
      refine my-leaf {
        mandatory true;
      }
    }
  }
}

7.13.2. The "refine" Statement

Some of the properties of each node in the grouping can be refined with the "refine" statement. The argument is a string that identifies a node in the grouping. This node is called the refine's target node. If a node in the grouping is not present as a target node of a "refine" statement, it is not refined and thus is used exactly as it was defined in the grouping.

The argument string is a descendant schema node identifier (see Section 6.5).

The following refinements can be done:

• A leaf or choice node may get a default value, or a new default value if it already had one.

• A leaf-list node may get a set of default values, or a new set of default values if it already had defaults; i.e., the set of refined default values replaces the defaults already given.

• Any node may get a specialized "description" string.

• Any node may get a specialized "reference" string.

• Any node may get a different "config" statement.

• A leaf, anydata, anyxml, or choice node may get a different "mandatory" statement.

• A container node may get a "presence" statement.

• A leaf, leaf-list, list, container, anydata, or anyxml node may get additional "must" expressions.

• A leaf-list or list node may get a different "min-elements" or "max-elements" statement.

• A leaf, leaf-list, list, container, choice, case, anydata, or anyxml node may get additional "if-feature" expressions.

• Any node can get refined extensions, if the extension allows refinement. See Section 7.19 for details.

RFC7950, Section 7.13.2