terraform: interpolate "terraform.env"

terraform/context.go

@@ -49,6 +49,7 @@ var (
 // ContextOpts are the user-configurable options to create a context with
 // NewContext.
 type ContextOpts struct {
+	Meta               *ContextMeta
 	Destroy            bool
 	Diff               *Diff
 	Hooks              []Hook
@@ -65,6 +66,14 @@ type ContextOpts struct {
 	UIInput UIInput
 }
 
+// ContextMeta is metadata about the running context. This is information
+// that this package or structure cannot determine on its own but exposes
+// into Terraform in various ways. This must be provided by the Context
+// initializer.
+type ContextMeta struct {
+	Env string // Env is the state environment
+}
+
 // Context represents all the context that Terraform needs in order to
 // perform operations on infrastructure. This structure is built using
 // NewContext. See the documentation for that.
@@ -80,6 +89,7 @@ type Context struct {
 	diff       *Diff
 	diffLock   sync.RWMutex
 	hooks      []Hook
+	meta       *ContextMeta
 	module     *module.Tree
 	sh         *stopHook
 	shadow     bool
@@ -178,6 +188,7 @@ func NewContext(opts *ContextOpts) (*Context, error) {
 		destroy:   opts.Destroy,
 		diff:      diff,
 		hooks:     hooks,
+		meta:      opts.Meta,
 		module:    opts.Module,
 		shadow:    opts.Shadow,
 		state:     state,
@@ -313,6 +324,7 @@ func (c *Context) Interpolater() *Interpolater {
 	var stateLock sync.RWMutex
 	return &Interpolater{
 		Operation:          walkApply,
+		Meta:               c.meta,
 		Module:             c.module,
 		State:              c.state.DeepCopy(),
 		StateLock:          &stateLock,

terraform/interpolate.go

@@ -25,6 +25,7 @@ const (
 // for interpolations such as `aws_instance.foo.bar`.
 type Interpolater struct {
 	Operation          walkOperation
+	Meta               *ContextMeta
 	Module             *module.Tree
 	State              *State
 	StateLock          *sync.RWMutex
@@ -87,6 +88,8 @@ func (i *Interpolater) Values(
 			err = i.valueSelfVar(scope, n, v, result)
 		case *config.SimpleVariable:
 			err = i.valueSimpleVar(scope, n, v, result)
+		case *config.TerraformVariable:
+			err = i.valueTerraformVar(scope, n, v, result)
 		case *config.UserVariable:
 			err = i.valueUserVar(scope, n, v, result)
 		default:
@@ -309,6 +312,25 @@ func (i *Interpolater) valueSimpleVar(
 		n)
 }
 
+func (i *Interpolater) valueTerraformVar(
+	scope *InterpolationScope,
+	n string,
+	v *config.TerraformVariable,
+	result map[string]ast.Variable) error {
+	if v.Field != "env" {
+		return fmt.Errorf(
+			"%s: only supported key for 'terraform.X' interpolations is 'env'", n)
+	}
+
+	if i.Meta == nil {
+		return fmt.Errorf(
+			"%s: internal error: nil Meta. Please report a bug.", n)
+	}
+
+	result[n] = ast.Variable{Type: ast.TypeString, Value: i.Meta.Env}
+	return nil
+}
+
 func (i *Interpolater) valueUserVar(
 	scope *InterpolationScope,
 	n string,

terraform/interpolate_test.go

@@ -893,6 +893,33 @@ func TestInterpolater_resourceUnknownVariableList(t *testing.T) {
 		interfaceToVariableSwallowError([]interface{}{}))
 }
 
+func TestInterpolater_terraformEnv(t *testing.T) {
+	i := &Interpolater{
+		Meta: &ContextMeta{Env: "foo"},
+	}
+
+	scope := &InterpolationScope{
+		Path: rootModulePath,
+	}
+
+	testInterpolate(t, i, scope, "terraform.env", ast.Variable{
+		Value: "foo",
+		Type:  ast.TypeString,
+	})
+}
+
+func TestInterpolater_terraformInvalid(t *testing.T) {
+	i := &Interpolater{
+		Meta: &ContextMeta{Env: "foo"},
+	}
+
+	scope := &InterpolationScope{
+		Path: rootModulePath,
+	}
+
+	testInterpolateErr(t, i, scope, "terraform.nope")
+}
+
 func testInterpolate(
 	t *testing.T, i *Interpolater,
 	scope *InterpolationScope,