go-template-utils

README

What is go-template-utils?

A library for processing Go templates in policy templates or other Open Cluster Management objects.

Go to the Contributing guide to learn how to get involved.

• The go-template-utils repository is part of the open-cluster-management community. For more information, visit: open-cluster-management.io.

How do templates work?

To get started, use the templates.NewResolver function along with a templates.Config instance.

See the ResolveTemplate example for an example of how to use this library.

Under the hood, go-template-utils wraps the text/template package. This means that as long as the input to templates.ResolveTemplate can be marshaled to YAML, any of the text/template package features can be used.

Additionally, the following custom functions are supported:

• atoi parses an input string and returns an integer like the Atoi function. For example, {{ "6" | atoi }}.
• autoindent will automatically indent the input string based on the leading spaces. For example, {{ "Templating\nrocks!" | autoindent }}.
• base64enc decodes the input Base64 string to its decoded form. For example, {{ "VGVtcGxhdGVzIHJvY2shCg==" | base64dec }}.
• base64enc encodes an input string in the Base64 format. For example, {{ "Templating rocks!" | base64enc }}.
• indent will indent the input string by specified amount. For example, {{ "Templating\nrocks!" | indent 4 }}.
• fromClusterClaim returns the value of a specific ClusterClaim. For example, {{ fromClusterClaim "name" }}.
• fromConfigMap returns the value of a key inside a ConfigMap. For example, {{ fromConfigMap "namespace" "config-map-name" "key" }}.
• fromSecret returns the value of a key inside a Secret. For example, {{ fromSecret "namespace" "secret-name" "key" }}. If the EncryptionMode is set to EncryptionEnabled, this will return an encrypted value.
• lookup is a generic lookup function for any Kubernetes object. For example, {{ (lookup "v1" "Secret" "namespace" "name").Data.key }}.
• protect is a function that encrypts any string using AES-CBC.
• toBool - parses an input boolean string converts it to a boolean but also removes any quotes around the map value. For example, key: "{{ "true" | toBool }}" => key: true.
• toInt parses an input string and returns an integer but also removes any quotes around the map value. For example, key: "{{ "6" | toInt }}" => key: 6.
• toLiteral removes any quotes around the template string after it is processed. For example, key: "{{ "[10.10.10.10, 1.1.1.1]" | toLiteral }} => key: [10.10.10.10, 1.1.1.1]. A good use-case for this is when a ConfigMap field contains a JSON string that you want to literally replace the template with and have it treated as the underlying JSON type.