config: validate module names are valid

config/config.go

@@ -241,9 +241,9 @@ func (c *Config) Validate() error {
 			}
 		}
 
+		if _, ok := modules[m.Id()]; !ok {
 			// If we haven't seen this module before, check that the
 			// source has no interpolations.
-		if _, ok := modules[m.Id()]; !ok {
 			rc, err := NewRawConfig(map[string]interface{}{
 				"root": m.Source,
 			})
@@ -256,6 +256,13 @@ func (c *Config) Validate() error {
 					"%s: module source cannot contain interpolations",
 					m.Id()))
 			}
+
+			// Check that the name matches our regexp
+			if !NameRegexp.Match([]byte(m.Name)) {
+				errs = append(errs, fmt.Errorf(
+					"%s: module name cannot contain special characters",
+					m.Id()))
+			}
 		}
 
 		modules[m.Id()] = m

config/config_test.go

@@ -123,6 +123,13 @@ func TestConfigValidate_dupResource(t *testing.T) {
 	}
 }
 
+func TestConfigValidate_moduleNameBad(t *testing.T) {
+	c := testConfig(t, "validate-module-name-bad")
+	if err := c.Validate(); err == nil {
+		t.Fatal("should not be valid")
+	}
+}
+
 func TestConfigValidate_moduleSourceVar(t *testing.T) {
 	c := testConfig(t, "validate-module-source-var")
 	if err := c.Validate(); err == nil {

config/test-fixtures/validate-module-name-bad/main.tf

@@ -0,0 +1,3 @@
+module "foo bar" {
+    source = "foo"
+}