Merge pull request #11099 from hashicorp/b-root-module

config/module: disallow root modules named "root"

config/module/test-fixtures/validate-module-root-grandchild/child/child/main.tf

@@ -0,0 +1 @@
+# Empty

config/module/test-fixtures/validate-module-root-grandchild/child/main.tf

@@ -0,0 +1 @@
+module "root" { source = "./child" }

config/module/test-fixtures/validate-module-root-grandchild/main.tf

@@ -0,0 +1,3 @@
+module "child" {
+    source = "./child"
+}

config/module/test-fixtures/validate-module-root/child/main.tf

@@ -0,0 +1 @@
+# Empty

config/module/test-fixtures/validate-module-root/main.tf

@@ -0,0 +1,3 @@
+module "root" {
+    source = "./child"
+}

config/module/tree.go

@@ -261,6 +261,14 @@ func (t *Tree) Validate() error {
 	// If something goes wrong, here is our error template
 	newErr := &TreeError{Name: []string{t.Name()}}
 
+	// Terraform core does not handle root module children named "root".
+	// We plan to fix this in the future but this bug was brought up in
+	// the middle of a release and we don't want to introduce wide-sweeping
+	// changes at that time.
+	if len(t.path) == 1 && t.name == "root" {
+		return fmt.Errorf("root module cannot contain module named 'root'")
+	}
+
 	// Validate our configuration first.
 	if err := t.config.Validate(); err != nil {
 		newErr.Err = err

config/module/tree_test.go

@@ -288,6 +288,18 @@ func TestTreeValidate_table(t *testing.T) {
 			"validate-alias-bad",
 			"alias must be defined",
 		},
+
+		{
+			"root module named root",
+			"validate-module-root",
+			"cannot contain module",
+		},
+
+		{
+			"grandchild module named root",
+			"validate-module-root-grandchild",
+			"",
+		},
 	}
 
 	for i, tc := range cases {