add test for unset variable

hcl2template/common_test.go

@@ -9,6 +9,7 @@ import (
 
 	"github.com/hashicorp/hcl/v2"
 	"github.com/hashicorp/hcl/v2/hclparse"
+	"github.com/hashicorp/packer/builder/null"
 	. "github.com/hashicorp/packer/hcl2template/internal"
 	"github.com/hashicorp/packer/helper/config"
 	"github.com/hashicorp/packer/packer"
@@ -21,6 +22,7 @@ func getBasicParser() *Parser {
 		BuilderSchemas: packer.MapOfBuilder{
 			"amazon-ebs":     func() (packer.Builder, error) { return &MockBuilder{}, nil },
 			"virtualbox-iso": func() (packer.Builder, error) { return &MockBuilder{}, nil },
+			"null":           func() (packer.Builder, error) { return &null.Builder{}, nil },
 		},
 		ProvisionersSchemas: packer.MapOfProvisioner{
 			"shell": func() (packer.Provisioner, error) { return &MockProvisioner{}, nil },

hcl2template/testdata/variables/unset_string_variable.pkr.hcl

@@ -0,0 +1,14 @@
+
+variable "foo" {
+  type = string
+}
+
+build {
+  sources = [
+    "source.null.null-builder",
+  ]
+}
+
+source "null" "null-builder" {
+  communicator = var.foo
+}

hcl2template/types.variables_test.go

@@ -10,6 +10,7 @@ import (
 	"github.com/zclconf/go-cty/cty/convert"
 
 	"github.com/hashicorp/hcl/v2"
+	"github.com/hashicorp/packer/builder/null"
 	"github.com/hashicorp/packer/packer"
 )
 
@@ -97,6 +98,34 @@ func TestParse_variables(t *testing.T) {
 			[]packer.Build{},
 			false,
 		},
+		{"unset variable",
+			defaultParser,
+			parseTestArgs{"testdata/variables/unset_string_variable.pkr.hcl", nil},
+			&PackerConfig{
+				Basedir: filepath.Join("testdata", "variables"),
+				InputVariables: Variables{
+					"foo": &Variable{},
+				},
+				Sources: map[SourceRef]*SourceBlock{
+					SourceRef{"null", "null-builder"}: &SourceBlock{
+						Name: "null-builder",
+						Type: "null",
+					},
+				},
+				Builds: Builds{
+					&BuildBlock{
+						Sources: []SourceRef{SourceRef{"null", "null-builder"}},
+					},
+				},
+			},
+			false, false,
+			[]packer.Build{
+				&packer.CoreBuild{
+					Builder: &null.Builder{},
+				},
+			},
+			false,
+		},
 	}
 	testParse(t, tests)
 }