config: validate no interp in var [GH-180]

CHANGELOG.md

@@ -1,6 +1,8 @@
 ## 0.2.0 (unreleased)
 
+BUG FIXES:
 
+  * core: Variables are validated to not contain interpolations. [GH-180]
 
 ## 0.1.1 (August 5, 2014)
 

config/config.go

@@ -9,6 +9,7 @@ import (
 	"github.com/hashicorp/terraform/flatmap"
 	"github.com/hashicorp/terraform/helper/multierror"
 	"github.com/mitchellh/mapstructure"
+	"github.com/mitchellh/reflectwalk"
 )
 
 // Config is the configuration that comes from loading a collection
@@ -116,6 +117,22 @@ func (c *Config) Validate() error {
 			errs = append(errs, fmt.Errorf(
 				"Variable '%s': must be string or mapping",
 				v.Name))
+			continue
+		}
+
+		interp := false
+		fn := func(i Interpolation) (string, error) {
+			interp = true
+			return "", nil
+		}
+
+		w := &interpolationWalker{F: fn}
+		if err := reflectwalk.Walk(v.Default, w); err == nil {
+			if interp {
+				errs = append(errs, fmt.Errorf(
+					"Variable '%s': cannot contain interpolations",
+					v.Name))
+			}
 		}
 	}
 

config/config_test.go

@@ -100,6 +100,13 @@ func TestConfigValidate_varDefaultBadType(t *testing.T) {
 	}
 }
 
+func TestConfigValidate_varDefaultInterpolate(t *testing.T) {
+	c := testConfig(t, "validate-var-default-interpolate")
+	if err := c.Validate(); err == nil {
+		t.Fatal("should not be valid")
+	}
+}
+
 func TestProviderConfigName(t *testing.T) {
 	pcs := []*ProviderConfig{
 		&ProviderConfig{Name: "aw"},

config/test-fixtures/validate-var-default-interpolate/main.tf

@@ -0,0 +1,3 @@
+variable "foo" {
+  default = "${aws_instance.foo.bar}"
+}