config: DefaultsMap

config/config.go

@@ -6,7 +6,9 @@ import (
 	"fmt"
 	"strings"
 
+	"github.com/hashicorp/terraform/flatmap"
 	"github.com/hashicorp/terraform/helper/multierror"
+	"github.com/mitchellh/mapstructure"
 )
 
 // Config is the configuration that comes from loading a collection
@@ -63,6 +65,14 @@ type Output struct {
 	RawConfig *RawConfig
 }
 
+type VariableType byte
+
+const (
+	VariableTypeUnknown VariableType = iota
+	VariableTypeString
+	VariableTypeMap
+)
+
 // ProviderConfigName returns the name of the provider configuration in
 // the given mapping that maps to the proper provider configuration
 // for this resource.
@@ -271,6 +281,20 @@ func (r *Resource) mergerMerge(m merger) merger {
 	return &result
 }
 
+// DefaultsMap returns a map of default values for this variable.
+func (v *Variable) DefaultsMap() map[string]string {
+	switch v.Type() {
+	case VariableTypeString:
+		return map[string]string{v.Name: v.Default.(string)}
+	case VariableTypeMap:
+		return flatmap.Flatten(map[string]interface{}{
+			v.Name: v.Default.(map[string]string),
+		})
+	default:
+		return nil
+	}
+}
+
 // Merge merges two variables to create a new third variable.
 func (v *Variable) Merge(v2 *Variable) *Variable {
 	// Shallow copy the variable
@@ -289,6 +313,27 @@ func (v *Variable) Merge(v2 *Variable) *Variable {
 	return &result
 }
 
+// Type returns the type of varialbe this is.
+func (v *Variable) Type() VariableType {
+	if v.Default == nil {
+		return VariableTypeString
+	}
+
+	var strVal string
+	if err := mapstructure.WeakDecode(v.Default, &strVal); err == nil {
+		v.Default = strVal
+		return VariableTypeString
+	}
+
+	var m map[string]string
+	if err := mapstructure.WeakDecode(v.Default, &m); err == nil {
+		v.Default = m
+		return VariableTypeMap
+	}
+
+	return VariableTypeUnknown
+}
+
 func (v *Variable) mergerName() string {
 	return v.Name
 }

config/config_test.go

@@ -2,6 +2,7 @@ package config
 
 import (
 	"path/filepath"
+	"reflect"
 	"testing"
 )
 
@@ -96,6 +97,37 @@ func TestProviderConfigName(t *testing.T) {
 	}
 }
 
+func TestVariableDefaultsMap(t *testing.T) {
+	cases := []struct {
+		Default interface{}
+		Output  map[string]string
+	}{
+		{
+			"foo",
+			map[string]string{"foo": "foo"},
+		},
+
+		{
+			map[interface{}]interface{}{
+				"foo": "bar",
+				"bar": "baz",
+			},
+			map[string]string{
+				"foo.foo": "bar",
+				"foo.bar": "baz",
+			},
+		},
+	}
+
+	for i, tc := range cases {
+		v := &Variable{Name: "foo", Default: tc.Default}
+		actual := v.DefaultsMap()
+		if !reflect.DeepEqual(actual, tc.Output) {
+			t.Fatalf("%d: bad: %#v", i, actual)
+		}
+	}
+}
+
 func testConfig(t *testing.T, name string) *Config {
 	c, err := Load(filepath.Join(fixtureDir, name, "main.tf"))
 	if err != nil {