config: validate that module variables can go to ints, convert [GH-624]

config/config.go

@@ -239,11 +239,14 @@ func (c *Config) Validate() error {
 					"%s: module repeated multiple times",
 					m.Id()))
 			}
+
+			// Already seen this module, just skip it
+			continue
 		}
 
-		if _, ok := modules[m.Id()]; !ok {
+		modules[m.Id()] = m
-			// If we haven't seen this module before, check that the
+
-			// source has no interpolations.
+		// Check that the source has no interpolations
 		rc, err := NewRawConfig(map[string]interface{}{
 			"root": m.Source,
 		})
@@ -264,9 +267,26 @@ func (c *Config) Validate() error {
 					"dashes, and underscores",
 				m.Id()))
 		}
+
+		// Check that the configuration can all be strings
+		raw := make(map[string]interface{})
+		for k, v := range m.RawConfig.Raw {
+			var strVal string
+			if err := mapstructure.WeakDecode(v, &strVal); err != nil {
+				errs = append(errs, fmt.Errorf(
+					"%s: variable %s must be a string value",
+					m.Id(), k))
+			}
+			raw[k] = strVal
 		}
 
-		modules[m.Id()] = m
+		// Update the raw configuration to only contain the string values
+		m.RawConfig, err = NewRawConfig(raw)
+		if err != nil {
+			errs = append(errs, fmt.Errorf(
+				"%s: can't initialize configuration: %s",
+				m.Id(), err))
+		}
 	}
 	dupped = nil
 

config/config_test.go

@@ -137,6 +137,20 @@ func TestConfigValidate_moduleSourceVar(t *testing.T) {
 	}
 }
 
+func TestConfigValidate_moduleVarInt(t *testing.T) {
+	c := testConfig(t, "validate-module-var-int")
+	if err := c.Validate(); err != nil {
+		t.Fatalf("should be valid: %s", err)
+	}
+}
+
+func TestConfigValidate_moduleVarMap(t *testing.T) {
+	c := testConfig(t, "validate-module-var-map")
+	if err := c.Validate(); err == nil {
+		t.Fatal("should be invalid")
+	}
+}
+
 func TestConfigValidate_nil(t *testing.T) {
 	var c Config
 	if err := c.Validate(); err != nil {

config/test-fixtures/validate-module-var-int/main.tf

@@ -0,0 +1,4 @@
+module "foo" {
+    source = "./foo"
+    nodes = 3
+}

config/test-fixtures/validate-module-var-map/main.tf

@@ -0,0 +1,4 @@
+module "foo" {
+    source = "./foo"
+    nodes = [1,2,3]
+}

terraform/terraform_test.go

@@ -932,6 +932,19 @@ STATE:
 <no state>
 `
 
+const testTerraformPlanModuleVarIntStr = `
+DIFF:
+
+module.child:
+  CREATE: aws_instance.foo
+    num:  "" => "2"
+    type: "" => "aws_instance"
+
+STATE:
+
+<no state>
+`
+
 const testTerraformPlanOrphanStr = `
 DIFF: