rule

Rule represents the expression which will be evaluated by CEL. ref: https://github.com/google/cel-spec The Rule is scoped to the location of the x-kubernetes-validations extension in the schema. The self variable in the CEL expression is bound to the scoped value. Example: - Rule scoped to the root of a resource with a status subresource: {"rule": "self.status.actual <= self.spec.maxDesired"} If the Rule is scoped to an object with properties, the accessible properties of the object are field selectable via self.field and field presence can be checked via has(self.field). Null valued fields are treated as absent fields in CEL expressions. If the Rule is scoped to an object with additionalProperties (i.e. a map) the value of the map are accessible via self[mapKey], map containment can be checked via mapKey in self and all entries of the map are accessible via CEL macros and functions such as self.all(...). If the Rule is scoped to an array, the elements of the array are accessible via self[i] and also by macros and functions. If the Rule is scoped to a scalar, self is bound to the scalar value. Examples: - Rule scoped to a map of objects: {"rule": "self.components'Widget'.priority < 10"} - Rule scoped to a list of integers: {"rule": "self.values.all(value, value >= 0 && value < 100)"} - Rule scoped to a string value: {"rule": "self.startsWith('kube')"} The apiVersion, kind, metadata.name and metadata.generateName are always accessible from the root of the object and from any x-kubernetes-embedded-resource annotated objects. No other metadata properties are accessible. Unknown data preserved in custom resources via x-kubernetes-preserve-unknown-fields is not accessible in CEL expressions. This includes: - Unknown field values that are preserved by object schemas with x-kubernetes-preserve-unknown-fields. - Object properties where the property schema is of an "unknown type". An "unknown type" is recursively defined as:

• A schema with no type and x-kubernetes-preserve-unknown-fields set to true

• An array where the items schema is of an "unknown type"

• An object where the additionalProperties schema is of an "unknown type" Only property names of the form [a-zA-Z_.-/][a-zA-Z0-9_.-/]* are accessible. Accessible property names are escaped according to the following rules when accessed in the expression: - '' escapes to 'underscores' - '.' escapes to 'dot' - '-' escapes to 'dash' - '/' escapes to 'slash' - Property names that exactly match a CEL RESERVED keyword escape to '{keyword}__'. The keywords are: "true", "false", "null", "in", "as", "break", "const", "continue", "else", "for", "function", "if", "import", "let", "loop", "package", "namespace", "return". Examples:

• Rule accessing a property named "namespace": {"rule": "self.namespace 0"}

• Rule accessing a property named "x-prop": {"rule": "self.x__dash__prop 0"}

• Rule accessing a property named "redact__d": {"rule": "self.redact__underscores__d 0"} Equality on arrays with x-kubernetes-list-type of 'set' or 'map' ignores element order, i.e. 1, 2 == 2, 1. Concatenation on arrays with x-kubernetes-list-type use the semantics of the list type:

• 'set': X + Y performs a union where the array positions of all elements in X are preserved and non-intersecting elements in Y are appended, retaining their partial order.

• 'map': X + Y performs a merge where the array positions of all keys in X are preserved but the values are overwritten by values in Y when the key sets of X and Y intersect. Elements in Y with non-intersecting keys are appended, retaining their partial order. If rule makes use of the oldSelf variable it is implicitly a transition rule. By default, the oldSelf variable is the same type as self. When optionalOldSelf is true, the oldSelf variable is a CEL optional variable whose value() is the same type as self. See the documentation for the optionalOldSelf field for details. Transition rules by default are applied only on UPDATE requests and are skipped if an old value could not be found. You can opt a transition rule into unconditional evaluation by setting optionalOldSelf to true.