Add env template helper (#121)

cmd/backup/notifications.go

@@ -7,6 +7,7 @@ import (
 	"bytes"
 	_ "embed"
 	"fmt"
+	"os"
 	"text/template"
 	"time"
 
@@ -82,6 +83,7 @@ var templateHelpers = template.FuncMap{
 	"formatBytesBin": func(bytes uint64) string {
 		return formatBytes(bytes, false)
 	},
+	"env": os.Getenv,
 }
 
 // formatBytes converts an amount of bytes in a human-readable representation

docs/NOTIFICATION-TEMPLATES.md

@@ -32,8 +32,9 @@ Here is a list of all data passed to the template:
 
 ## Functions
 
-Some formatting functions are also available:
+Some formatting and helper functions are also available:
 
 * `formatTime`: formats a time object using [RFC3339](https://datatracker.ietf.org/doc/html/rfc3339) format (e.g. `2022-02-11T01:00:00Z`)
 * `formatBytesBin`: formats an amount of bytes using powers of 1024 (e.g. `7055258` bytes will be `6.7 MiB`) 
 * `formatBytesDec`: formats an amount of bytes using powers of 1000 (e.g. `7055258` bytes will be `7.1 MB`)
+* `env`: returns the value of the environment variable of the given key if set

test/notifications/docker-compose.yml

@@ -10,6 +10,7 @@ services:
       BACKUP_PRUNING_PREFIX: test
       NOTIFICATION_LEVEL: info
       NOTIFICATION_URLS: ${NOTIFICATION_URLS}
+      EXTRA_VALUE: extra-value
     volumes:
       - ./local:/archive
       - app_data:/backup/app_data:ro

test/notifications/notifications.tmpl

@@ -1,5 +1,5 @@
 {{ define "title_success" -}}
-Successful test run, yay!
+Successful test run with {{ env "EXTRA_VALUE" }}, yay!
 {{- end }}
 
 {{ define "body_success" -}}

test/notifications/run.sh

@@ -37,7 +37,7 @@ pass "Correct number of notifications were sent when configured."
 MESSAGE_TITLE=$(curl -sSL http://admin:custom@localhost:8080/message | jq -r '.messages[0].title')
 MESSAGE_BODY=$(curl -sSL http://admin:custom@localhost:8080/message | jq -r '.messages[0].message')
 
-if [ "$MESSAGE_TITLE" != "Successful test run, yay!" ]; then
+if [ "$MESSAGE_TITLE" != "Successful test run with extra-value, yay!" ]; then
   fail "Unexpected notification title $MESSAGE_TITLE"
 fi
 pass "Custom notification title was used."