Structure value validation

[cueckoo]

Originally opened by @dariada in cuelang/cue#392

Hey, I have a ConfigMap file that contains a data block of string and number variables.
Is there a way to to check that the value meets certain conditions but does not limit the field name?

For example,
For fields that are string check that they contain quotes at the beginning and end without referring to the field name itself so we can add new fields without describing each one.

apiVersion: v1
kind: ConfigMap
metadata:
  name: environment
  namespace: backend
data:
  NAME_SEPARATOR: "_"
  DB_HOST: some_string
  POSTRESQL_HOST: some_string
  POSTRESQL_PORT: "5432"
  MYSQL_PORT: "3306"
  REDIS_PORT: "6379"
  ENV_NAME: "staging"
  LOG_FORMAT: "json"

[cueckoo]

Original reply by @seh in cuelang/cue#392 (comment)

When parsing this YAML, the quotation marks surrounding the string values are consumed and discarded by the parser. Your view of the imported data within CUE won't be able to tell the difference between the YAML values having been quoted or not.

Was your goal to preclude there being any values that parse as numbers as opposed to strings?

[cueckoo]

Original reply by @dariada in cuelang/cue#392 (comment)

Our goal is to create a general structure of the string variables without specifying each variable individually by name.
For example, we want to check that all string type variables under the data block meet certain conditions like quotation marks.

[cueckoo]

Original reply by @seh in cuelang/cue#392 (comment)

To permit those optional fields, you could introduce definitions like the following:

import (
        corev1 "k8s.io/api/core/v1"
)

#rfc1123: #subdomainLength: 253

#ConfigMap: {
            corev1.#ConfigMap

            // See https://sourcegraph.com/github.com/kubernetes/kubernetes@master/-/blob/staging/src/k8s.io/apimachinery/pkg/util/validation/validation.go#L418-L429.
            #configMapKey: =~"^[-._[:alnum:]]{1,\(#rfc1123.#subdomainLength)}$"
            // As an example, mandate that all values start with "foo-".
            data: [#configMapKey]: =~"^foo-"
}

Note the =~ "^foo-" constraint on the values for fields within the "data" field. You can build up more complex constraints there to meet your needs.

Again, though, trying to differentiate between quoted and unquoted strings as written in YAML won't work here.

[cueckoo]

Original reply by @seh in cuelang/cue#392 (comment)

Note that you can also add such restrictions under your cue.mod/usr tree to the generated definitions like corev1.ConfigMap as shown above.