From fe2a3063418a54c2e744dd59bf1e48ed498cc0d5 Mon Sep 17 00:00:00 2001
From: Mitchell Hashimoto <mitchell.hashimoto@gmail.com>
Date: Mon, 11 Aug 2014 09:46:56 -0700
Subject: [PATCH] config: validate no interp in var [GH-180]

---
 CHANGELOG.md                                    |  2 ++
 config/config.go                                | 17 +++++++++++++++++
 config/config_test.go                           |  7 +++++++
 .../validate-var-default-interpolate/main.tf    |  3 +++
 4 files changed, 29 insertions(+)
 create mode 100644 config/test-fixtures/validate-var-default-interpolate/main.tf

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 32d2581639..c26461b206 100644
--- a/CHANGELOG.md
+++ b/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)
 
diff --git a/config/config.go b/config/config.go
index 6e01c4231c..b89ffcf297 100644
--- a/config/config.go
+++ b/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))
+			}
 		}
 	}
 
diff --git a/config/config_test.go b/config/config_test.go
index e5b6653a97..84f10a528e 100644
--- a/config/config_test.go
+++ b/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"},
diff --git a/config/test-fixtures/validate-var-default-interpolate/main.tf b/config/test-fixtures/validate-var-default-interpolate/main.tf
new file mode 100644
index 0000000000..f9dfe151ec
--- /dev/null
+++ b/config/test-fixtures/validate-var-default-interpolate/main.tf
@@ -0,0 +1,3 @@
+variable "foo" {
+  default = "${aws_instance.foo.bar}"
+}