Go template list variable to replace from template - go

Question

So I'm using go template and I would like to be able to generate a configmap dynamically by getting the list of the variable from the template.
To be precise, let's say I have a file name test.yaml.tmpl that looks something like that:
car:
color: {{ .color }}
model: {{ .model }}
I would like to be able to generate an array in my go code containing [color model] or [.color .model] , I can work with the dots myself.
I looked at the differents options but I could not get the result I want, the closest I got was using template.Root.Nodes to extract the variable value but it's not perfect and may generate unwanted error in specific conditions.
Does someone has a clean way to generate an array of the template variable?
EDIT 1
I tried to use the tree, and that gives me this type of output:
&{test.yaml.tmpl test.yaml.tmpl ---
car:
color: {{ .color }}
model: {{ .model }}
0 ---
car:
color: {{ .color }}
model: {{ .model }}
[] <nil> [{8 995 45} {11 409 {{ 22} {0 0 0}] 1 [] map[] 0 0}
The issue is that I don't get to access the fields node the only methods available when accessing the tree are:
ErrorContext
Parse
Copy and it's methods
Mode
Name
ParseName
Root and the NodeType method
Still can't get the list of fields.
EDIT 2
When printing the tree.Root.Nodes I get the full yaml output with the variables to replace like that:
(*parse.ActionNode)(0xc00007f1d0)({{ .color }}),
(*parse.TextNode)(0xc00007f200)

Answer 1

Well you can user regex you know. ;P
package main
import (
"fmt"
"regexp"
)
var fieldSearch = regexp.MustCompile(`{{ \..* }}`)
func main() {
template := `
car:
color: {{ .color }}
model: {{ .model }}
`
res := fieldSearch.FindAll([]byte(template), -1)
for i := range res {
// this is just for readability you can replace this with
// magic numbers if you want
res[i] = res[i][len("{{ .") : len(res[i])-len(" }}")]
}
for _, v := range res {
fmt.Println(string(v))
}
}

Answer 2

Ok, so I used the link posted by #icza How to get a map or list of template 'actions' from a parsed template?and treated the returned string to get what I need, this resulted in the following:
func main() {
node := listNodeFields(t.Tree.Root)
var tNode []string
for _, n := range node {
r := n[len("{{.* .") : len(n)-len(" .*}}")]
if strings.Contains(n, "or ") {
r = r + " or"
}
tNode = append(tNode, r)
}
config := make(map[string]string)
for _, n := range tNode {
var value string
var present bool
if strings.Contains(n, " or") {
n = strings.Replace(n, " or", "", -1)
value, present = os.LookupEnv(n)
if !present {
fmt.Println("The variable " + value + " is not set but there is a default value in template " + t.Name() + "!")
}
} else {
value, present = os.LookupEnv(n)
if !present {
return nil, errors.New("The variable " + f + " is not set but exists in the template " + t.Name() + "!")
}
}
config[n] = value
}
}
func listNodeFields(node parse.Node) []string {
var res []string
if node.Type() == parse.NodeAction {
res = append(res, node.String())
}
if ln, ok := node.(*parse.ListNode); ok {
for _, n := range ln.Nodes {
res = append(res, listNodeFields(n)...)
}
}
return res
}
As I don't want to generate errors in case I'm using default value I added a specific treatment to not get errors from the missingkey=error option of the template.