terraform: warn if the name has special characters

terraform/context.go

@@ -1049,6 +1049,16 @@ func (c *walkContext) validateWalkFn() depgraph.WalkFunc {
 				return nil
 			}
 
+			// If the resouce name doesn't match the name regular
+			// expression, show a warning.
+			if !config.NameRegexp.Match([]byte(rn.Config.Name)) {
+				l.Lock()
+				meta.Warns = append(meta.Warns, fmt.Sprintf(
+					"'%s' warning: name can't contain special characters",
+					rn.Resource.Id))
+				l.Unlock()
+			}
+
 			log.Printf("[INFO] Validating resource: %s", rn.Resource.Id)
 			ws, es := rn.Resource.Provider.ValidateResource(
 				rn.Resource.Info.Type, rn.Resource.Config)

terraform/context_test.go

@@ -312,6 +312,25 @@ func TestContextValidate_resourceConfig_good(t *testing.T) {
 	}
 }
 
+func TestContextValidate_resourceNameSymbol(t *testing.T) {
+	p := testProvider("aws")
+	m := testModule(t, "validate-resource-name-symbol")
+	c := testContext(t, &ContextOpts{
+		Module: m,
+		Providers: map[string]ResourceProviderFactory{
+			"aws": testProviderFuncFixed(p),
+		},
+	})
+
+	w, e := c.Validate()
+	if len(w) == 0 {
+		t.Fatalf("bad: %#v", w)
+	}
+	if len(e) > 0 {
+		t.Fatalf("bad: %#v", e)
+	}
+}
+
 func TestContextValidate_requiredVar(t *testing.T) {
 	m := testModule(t, "validate-required-var")
 	c := testContext(t, &ContextOpts{

terraform/test-fixtures/validate-resource-name-symbol/main.tf

@@ -0,0 +1,3 @@
+resource "aws_instance" "foo bar" {
+    num = "2"
+}