hcp: use HCP_PACKER_REGISTRY to disable HCP

The current behaviour for HCP integration is based on the presence of
the HCP_PACKER_REGISTRY environment variable, where if it is either not
"0" or "off", the HCP integration is enabled.

This commit changes the behaviour to only use this variable to
explicitely disable HCP, and the HCP_PACKER_BUCKET_NAME variable will
condition if the HCP integration is enabled for a build or not in JSON
templates.

For HCL templates, the integration can also be disabled if the
HCP_PACKER_REGISTRY variable is set to "0" or "off", and will be
considered enabled if the HCP_PACKER_BUCKET_NAME is set, or there is a
"hcp_packer_registry" block in a build.

command/registry.go

@@ -47,6 +47,10 @@ func TrySetupHCP(cfg packer.Handler) hcl.Diagnostics {
 func setupRegistryForPackerConfig(pc *hcl2template.PackerConfig) hcl.Diagnostics {
 	var diags hcl.Diagnostics
 
+	if env.IsHCPDisabled() {
+		return nil
+	}
+
 	hasHCP := false
 
 	for _, build := range pc.Builds {
@@ -55,6 +59,14 @@ func setupRegistryForPackerConfig(pc *hcl2template.PackerConfig) hcl.Diagnostics
 		}
 	}
 
+	if env.HasPackerRegistryBucket() {
+		hasHCP = true
+	}
+
+	if !hasHCP {
+		return nil
+	}
+
 	if hasHCP && len(pc.Builds) > 1 {
 		diags = append(diags, &hcl.Diagnostic{
 			Severity: hcl.DiagError,
@@ -67,14 +79,6 @@ func setupRegistryForPackerConfig(pc *hcl2template.PackerConfig) hcl.Diagnostics
 		return diags
 	}
 
-	if env.IsPAREnabled() {
-		hasHCP = true
-	}
-
-	if !hasHCP {
-		return diags
-	}
-
 	var err error
 	pc.Bucket, err = registry.NewBucketWithIteration(registry.IterationOptions{
 		TemplateBaseDir: pc.Basedir,
@@ -111,6 +115,14 @@ func setupRegistryForPackerConfig(pc *hcl2template.PackerConfig) hcl.Diagnostics
 		}
 	}
 
+	if pc.Bucket.Slug == "" {
+		return append(diags, &hcl.Diagnostic{
+			Summary:  "bucket name cannot be empty",
+			Detail:   "empty bucket name, please set it with the HCP_PACKER_BUCKET_NAME environment variable, or in a `hcp_packer_registry` block",
+			Severity: hcl.DiagError,
+		})
+	}
+
 	vals, diags := pc.Datasources.Values()
 	if diags != nil {
 		return diags
@@ -254,7 +266,11 @@ func iterValueToDSOutput(iterVal map[string]cty.Value) iterds.DatasourceOutput {
 }
 
 func setupRegistryForPackerCore(cfg *CoreWrapper) hcl.Diagnostics {
-	if !env.IsPAREnabled() {
+	if env.IsHCPDisabled() {
+		return nil
+	}
+
+	if !env.HasPackerRegistryBucket() {
 		return nil
 	}
 
@@ -276,6 +292,14 @@ func setupRegistryForPackerCore(cfg *CoreWrapper) hcl.Diagnostics {
 	}
 	core.Bucket.LoadDefaultSettingsFromEnv()
 
+	if core.Bucket.Slug == "" {
+		return append(diags, &hcl.Diagnostic{
+			Summary:  "bucket name cannot be empty",
+			Detail:   "empty bucket name, please set it with the HCP_PACKER_BUCKET_NAME environment variable",
+			Severity: hcl.DiagError,
+		})
+	}
+
 	for _, b := range core.Template.Builders {
 		// Get all builds slated within config ignoring any only or exclude flags.
 		core.Bucket.RegisterBuildForComponent(b.Name)

internal/registry/env/env.go

@@ -6,18 +6,23 @@ import (
 )
 
 func HasClientID() bool {
-	_, ok := os.LookupEnv(HCPClientID)
-	return ok
+	return hasEnvVar(HCPClientID)
 }
 
 func HasClientSecret() bool {
-	_, ok := os.LookupEnv(HCPClientSecret)
-	return ok
+	return hasEnvVar(HCPClientSecret)
 }
 
 func HasPackerRegistryBucket() bool {
-	_, ok := os.LookupEnv(HCPPackerBucket)
-	return ok
+	return hasEnvVar(HCPPackerBucket)
+}
+
+func hasEnvVar(varName string) bool {
+	val, ok := os.LookupEnv(varName)
+	if !ok {
+		return false
+	}
+	return val != ""
 }
 
 func HasHCPCredentials() bool {
@@ -35,7 +40,7 @@ func HasHCPCredentials() bool {
 	return true
 }
 
-func IsPAREnabled() bool {
-	val, ok := os.LookupEnv(HCPPackerRegistry)
-	return ok && strings.ToLower(val) != "off" && val != "0"
+func IsHCPDisabled() bool {
+	hcp, ok := os.LookupEnv(HCPPackerRegistry)
+	return ok && strings.ToLower(hcp) == "off" || hcp == "0"
 }

internal/registry/env/env_test.go

@@ -1,50 +1,46 @@
 package env
 
 import (
-	"os"
 	"testing"
 )
 
-func Test_IsPAREnabled(t *testing.T) {
+func Test_IsHCPDisabled(t *testing.T) {
 	tcs := []struct {
-		name   string
-		value  string
-		output bool
+		name           string
+		registry_value string
+		output         bool
 	}{
 		{
-			name:   "set with 1",
-			value:  "1",
-			output: true,
+			name:           "nothing set",
+			registry_value: "",
+			output:         false,
 		},
 		{
-			name:   "set with ON",
-			value:  "ON",
-			output: true,
+			name:           "registry set with 1",
+			registry_value: "1",
+			output:         false,
 		},
 		{
-			name:   "set with 0",
-			value:  "0",
-			output: false,
+			name:           "registry set with 0",
+			registry_value: "0",
+			output:         true,
 		},
 		{
-			name:   "set with OFF",
-			value:  "OFF",
-			output: false,
+			name:           "registry set with OFF",
+			registry_value: "OFF",
+			output:         true,
 		},
 		{
-			name:   "unset",
-			value:  "",
-			output: false,
+			name:           "registry set with off",
+			registry_value: "off",
+			output:         true,
 		},
 	}
 
 	for _, tc := range tcs {
 		t.Run(tc.name, func(t *testing.T) {
-			if tc.value != "" {
-				_ = os.Setenv(HCPPackerRegistry, tc.value)
-				defer os.Unsetenv(HCPPackerRegistry)
-			}
-			out := IsPAREnabled()
+			t.Setenv(HCPPackerRegistry, tc.registry_value)
+			out := IsHCPDisabled()
 			if out != tc.output {
 				t.Fatalf("unexpected output: %t", out)
 			}