Merge pull request #541 from tmeckel/feat/custom_resource_build_prefix

feat: support setting custom_resource_build_prefix via environment variable

Author: tanmay-hc

.web-docs/components/builder/arm/README.md

@@ -523,6 +523,9 @@ Providing `temp_resource_group_name` or `location` in combination with
 - `custom_resource_build_prefix` (string) - specify custom azure resource names during build limited to max 10 characters
   this will set the prefix for the resources. The actual resource names will be
   `custom_resource_build_prefix` + resourcetype + 5 character random alphanumeric string
+  
+  You can also set this via the environment variable `PACKER_AZURE_CUSTOM_RESOURCE_BUILD_PREFIX`.
+  If both the config field and the environment variable are present, the config field takes precedence.
 
 - `license_type` (string) - Specify a license type for the build VM to enable Azure Hybrid Benefit. If not set, Pay-As-You-Go license
   model (default) will be used. Valid values are:

builder/azure/arm/config.go

@@ -614,6 +614,9 @@ type Config struct {
 	// specify custom azure resource names during build limited to max 10 characters
 	// this will set the prefix for the resources. The actual resource names will be
 	// `custom_resource_build_prefix` + resourcetype + 5 character random alphanumeric string
+	//
+	// You can also set this via the environment variable `PACKER_AZURE_CUSTOM_RESOURCE_BUILD_PREFIX`.
+	// If both the config field and the environment variable are present, the config field takes precedence.
 	CustomResourcePrefix string `mapstructure:"custom_resource_build_prefix" required:"false"`
 
 	// Specify a license type for the build VM to enable Azure Hybrid Benefit. If not set, Pay-As-You-Go license
@@ -1431,6 +1434,12 @@ func assertRequiredParametersSet(c *Config, errs *packersdk.MultiError) {
 		}
 	}
 
+	if c.CustomResourcePrefix == "" {
+		val, ok := os.LookupEnv("PACKER_AZURE_CUSTOM_RESOURCE_BUILD_PREFIX")
+		if ok {
+			c.CustomResourcePrefix = val
+		}
+	}
 	if c.CustomResourcePrefix != "" {
 		if ok, err := assertResourceNamePrefix(c.CustomResourcePrefix, "custom_resource_build_prefix"); !ok {
 			errs = packersdk.MultiErrorAppend(errs, err)

builder/azure/arm/config_test.go

@@ -2772,6 +2772,56 @@ func TestConfigShouldAcceptValidCustomResourceBuildPrefix(t *testing.T) {
 	}
 }
 
+func TestEnvVarSetsCustomResourceBuildPrefix_Invalid(t *testing.T) {
+	// Invalid env var should cause validation to fail when field not explicitly set
+	t.Setenv("PACKER_AZURE_CUSTOM_RESOURCE_BUILD_PREFIX", "pkr_123456")
+
+	config := map[string]interface{}{
+		"location":               "ignore",
+		"subscription_id":        "ignore",
+		"image_offer":            "ignore",
+		"image_publisher":        "ignore",
+		"image_sku":              "ignore",
+		"os_type":                "linux",
+		"resource_group_name":    "ignore",
+		"storage_account":        "ignore",
+		"capture_container_name": "ignore",
+		"capture_name_prefix":    "ignore",
+	}
+
+	var c Config
+	if _, err := c.Prepare(config, getPackerConfiguration()); err == nil {
+		t.Fatal("expected config to reject invalid env var value for custom_resource_build_prefix")
+	}
+}
+
+func TestConfigCustomResourceBuildPrefixTakesPrecedenceOverEnv(t *testing.T) {
+	// When both are present, the config value should win
+	t.Setenv("PACKER_AZURE_CUSTOM_RESOURCE_BUILD_PREFIX", "pkr-env99")
+
+	config := map[string]interface{}{
+		"location":                     "ignore",
+		"subscription_id":              "ignore",
+		"image_offer":                  "ignore",
+		"image_publisher":              "ignore",
+		"image_sku":                    "ignore",
+		"os_type":                      "linux",
+		"resource_group_name":          "ignore",
+		"storage_account":              "ignore",
+		"capture_container_name":       "ignore",
+		"capture_name_prefix":          "ignore",
+		"custom_resource_build_prefix": "pkr-12345-",
+	}
+
+	var c Config
+	if _, err := c.Prepare(config, getPackerConfiguration()); err != nil {
+		t.Fatalf("expected config to succeed when both env and config set, got error: %s", err)
+	}
+	if c.CustomResourcePrefix != "pkr-12345-" {
+		t.Fatalf("expected CustomResourcePrefix to be set from config (precedence), got %q", c.CustomResourcePrefix)
+	}
+}
+
 func TestConfigShouldNormalizeLicenseTypeCase(t *testing.T) {
 	config := map[string]string{
 		"capture_name_prefix":    "ignore",

docs-partials/builder/azure/arm/Config-not-required.mdx

@@ -385,6 +385,9 @@
 - `custom_resource_build_prefix` (string) - specify custom azure resource names during build limited to max 10 characters
   this will set the prefix for the resources. The actual resource names will be
   `custom_resource_build_prefix` + resourcetype + 5 character random alphanumeric string
+  
+  You can also set this via the environment variable `PACKER_AZURE_CUSTOM_RESOURCE_BUILD_PREFIX`.
+  If both the config field and the environment variable are present, the config field takes precedence.
 
 - `license_type` (string) - Specify a license type for the build VM to enable Azure Hybrid Benefit. If not set, Pay-As-You-Go license
   model (default) will be used. Valid values are: