command: test multi-state with default only to single state

command/meta_backend_migrate.go

@@ -67,7 +67,6 @@ func (m *Meta) backendMigrateState(opts *backendMigrateOpts) error {
 		// If the source only has one state and it is the default,
 		// treat it as if it doesn't support multi-state.
 		if len(oneStates) == 1 && oneStates[0] == backend.DefaultStateName {
-			panic("YO")
 			return m.backendMigrateState_s_s(opts)
 		}
 

command/meta_backend_test.go

@@ -1008,6 +1008,62 @@ func TestMetaBackend_configuredChangeCopy_singleState(t *testing.T) {
 	}
 }
 
+// Changing a configured backend that supports multi-state to a
+// backend that only supports single states. The multi-state only has
+// a default state.
+func TestMetaBackend_configuredChangeCopy_multiToSingleDefault(t *testing.T) {
+	// Create a temporary working directory that is empty
+	td := tempDir(t)
+	copy.CopyDir(testFixturePath("backend-change-multi-default-to-single"), td)
+	defer os.RemoveAll(td)
+	defer testChdir(t, td)()
+
+	// Register the single-state backend
+	backendinit.Set("local-single", backendlocal.TestNewLocalSingle)
+	defer backendinit.Set("local-single", nil)
+
+	// Ask input
+	defer testInputMap(t, map[string]string{
+		"backend-migrate-to-new":        "yes",
+		"backend-migrate-copy-to-empty": "yes",
+	})()
+
+	// Setup the meta
+	m := testMetaBackend(t, nil)
+
+	// Get the backend
+	b, err := m.Backend(&BackendOpts{Init: true})
+	if err != nil {
+		t.Fatalf("bad: %s", err)
+	}
+
+	// Check the state
+	s, err := b.State(backend.DefaultStateName)
+	if err != nil {
+		t.Fatalf("bad: %s", err)
+	}
+	if err := s.RefreshState(); err != nil {
+		t.Fatalf("bad: %s", err)
+	}
+	state := s.State()
+	if state == nil {
+		t.Fatal("state should not be nil")
+	}
+	if state.Lineage != "backend-change" {
+		t.Fatalf("bad: %#v", state)
+	}
+
+	// Verify no local state
+	if _, err := os.Stat(DefaultStateFilename); err == nil {
+		t.Fatal("file should not exist")
+	}
+
+	// Verify no local backup
+	if _, err := os.Stat(DefaultStateFilename + DefaultBackupExtension); err == nil {
+		t.Fatal("file should not exist")
+	}
+}
+
 // Unsetting a saved backend
 func TestMetaBackend_configuredUnset(t *testing.T) {
 	// Create a temporary working directory that is empty

command/test-fixtures/backend-change-multi-default-to-single/.terraform/terraform.tfstate

@@ -0,0 +1,22 @@
+{
+    "version": 3,
+    "serial": 0,
+    "lineage": "666f9301-7e65-4b19-ae23-71184bb19b03",
+    "backend": {
+        "type": "local",
+        "config": {
+            "path": "local-state.tfstate"
+        },
+        "hash": 9073424445967744180
+    },
+    "modules": [
+        {
+            "path": [
+                "root"
+            ],
+            "outputs": {},
+            "resources": {},
+            "depends_on": []
+        }
+    ]
+}

command/test-fixtures/backend-change-multi-default-to-single/local-state.tfstate

@@ -0,0 +1,6 @@
+{
+    "version": 3,
+    "terraform_version": "0.8.2",
+    "serial": 7,
+    "lineage": "backend-change"
+}

command/test-fixtures/backend-change-multi-default-to-single/main.tf

@@ -0,0 +1,5 @@
+terraform {
+    backend "local-single" {
+        path = "local-state-2.tfstate"
+    }
+}