While undoubtedly popular for distributing customizable Kubernetes manifests, Helm has somewhat of a bad reputation among those who need to author charts, not least because of the way it fundamentally works: plain text templating of yaml without awareness of what they represent.
Timoni is an attempt to address that: while it shares the same general structure and purpose with Helm, instead of text templating, everything passes through cue as structured data.
From a high level of how it works:
timoni.cue pulls together user config from values.cue validated against a #Config typedef,
along with an instantiation of objects to apply defined in #Instance merged with concrete config values.
For module (chart) authors:
#Config defines all the values users can be expected to input,
and #Instance.objects defines all the resources to apply.
Unlike helm where you typically instantiate the resource directly in its own file,
individual resources are defined as typedefs.
As an example:
1// templates/mydeployment.cue
2#MyDeployment & appsv1.#Deployment {
3 #config: #Config // input arg: values from user input
4 apiVersion: "apps/v1"
5 kind: "Deployment"
6 metadata: #config.metadata // use values from config / values
7 spec: appsv1.#DeploymentSpec & {
8 // ... actual deployment spec in here
9 }
10}
11
12// templates/config.cue
13#Config: { // define args to the module
14 // bunch of built in fields
15 metadata: timoniv1.#Metadata & {#Version: moduleVersion}
16 metadata: labels: timoniv1.#Labels
17 metadata: annotations?: timoniv1.#Annotations
18}
19
20#Instance: {
21 config: #Config // args to this instance
22 objects: {
23 // actually use the deployment defined above,
24 // passing through config to it.
25 some_identifier: #MyDeployment & {#config: config}
26 }
27}
28
29// timoni.cue
30// user input, validate against #Config
31values: templates.#Config
32
33timoni: {
34 instance: templates.#Instance & {
35 config: values // pass config to an instance
36 }
37
38 // render out the objects from the instance to apply
39 apply: app: [for obj in instance.objects {obj}]
40}
Timoni is at the same time too dynamic (it allows runtime queries for values), and not flexible enough (the options you have are what the chart author exposed). It's a marginal improvement for chart authors in the natural validation you get from types, but there's not much benefit to end users.