Go template if condition

Question content

How to combine the and and eq/ne functions together?

I wrote this fragment

{{ define "opsgenie.default.tmpl" }}
  <font size="+0"><b>{{.commonlabels.alertname }}</b></font>
  {{- range $i, $alert := .alerts }}
  <font size="+0">{{ .annotations.description }}</font>
  {{- end -}}
  {{- "\n" -}}
  {{- "\n" -}}
  {{- if and eq .commonlabels.infoalert "true" eq .commonlabels.topic "database" -}}
  grafana: https://{{ .commonlabels.url }}
  {{- "\n" -}}{{- end -}}
  {{- if and ne .commonlabels.infoalert "true" eq .commonlabels.topic "database" -}}
  database:
    • https://{{ .commonlabels.url }}/
    • https://{{ .commonlabels.url }}/
  {{- "\n" -}}{{- end -}}
  {{- end -}}
  {{- end -}}
{{- end -}}

The target is:

• If my alert contains two labels infoalert: true and topic:database then only the grafana link will be shown
• If my alert only contains the tag topic: database but not infoalert: true then only the databsse link will be shown

It looks like the conditional {{- if and eq .commonlabels.infoalert "true" eq .commonlabels.topic "database" -}} has incorrect syntax because I am getting Getting fired with this error in alertmanager.log:

notify retry canceled due to unrecoverable error after 1 attempts: templating error: template: email.tmpl:24:17: executing \"opsgenie.default.tmpl\" at <eq>: wrong number of args for eq: want at least 1 got 0

Correct answer

Just use parentheses to group expressions:

{{- if and (eq .commonlabels.infoalert "true") (eq .commonlabels.topic "database") -}}

{{- if and (ne .commonlabels.infoalert "true") (eq .commonlabels.topic "database") -}}

Check out this testable example:

func main() {
    t := template.must(template.new("").parse(src))

    m := map[string]any{
        "infoalert": "true",
        "topic":     "database",
    }
    if err := t.execute(os.stdout, m); err != nil {
        panic(err)
    }

    fmt.println("second round")
    m["infoalert"] = "false"
    if err := t.execute(os.stdout, m); err != nil {
        panic(err)
    }
}

const src = `
{{- if and (eq .infoalert "true") (eq .topic "database") -}}
    infoalert is true and topic is database
{{- end -}}
{{- if and (ne .infoalert "true") (eq .topic "database") -}}
    infoalert is not true and topic is database
{{ end }}
`

This will output (try it on go playground):

infoalert is true and topic is database
Second round
infoalert is NOT true and topic is database

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