Merge pull request #13258 from hashicorp/jbardin/local-init

don't delete local state on a local backend

command/meta_backend.go

@@ -1002,7 +1002,8 @@ func (m *Meta) backend_C_r_s(
 	}
 
 	// If the local state is not empty, we need to potentially do a
-	// state migration to the new backend (with user permission).
+	// state migration to the new backend (with user permission), unless the
+	// destination is also "local"
 	if localS := localState.State(); !localS.Empty() {
 		// Perform the migration
 		err = m.backendMigrateState(&backendMigrateOpts{
@@ -1015,12 +1016,27 @@ func (m *Meta) backend_C_r_s(
 			return nil, err
 		}
 
-		// We always delete the local state
+		// we usually remove the local state after migration to prevent
-		if err := localState.WriteState(nil); err != nil {
+		// confusion, but adding a default local backend block to the config
-			return nil, fmt.Errorf(errBackendMigrateLocalDelete, err)
+		// can get us here too. Don't delete our state if the old and new paths
+		// are the same.
+		erase := true
+		if newLocalB, ok := b.(*backendlocal.Local); ok {
+			if localB, ok := localB.(*backendlocal.Local); ok {
+				if newLocalB.StatePath == localB.StatePath {
+					erase = false
+				}
+			}
 		}
-		if err := localState.PersistState(); err != nil {
+
-			return nil, fmt.Errorf(errBackendMigrateLocalDelete, err)
+		if erase {
+			// We always delete the local state, unless that was our new state too.
+			if err := localState.WriteState(nil); err != nil {
+				return nil, fmt.Errorf(errBackendMigrateLocalDelete, err)
+			}
+			if err := localState.PersistState(); err != nil {
+				return nil, fmt.Errorf(errBackendMigrateLocalDelete, err)
+			}
 		}
 	}
 

command/meta_backend_test.go

@@ -3275,6 +3275,51 @@ func TestMetaBackend_configureWithExtra(t *testing.T) {
 	}
 }
 
+// when confniguring a default local state, don't delete local state
+func TestMetaBackend_localDoesNotDeleteLocal(t *testing.T) {
+	// Create a temporary working directory that is empty
+	td := tempDir(t)
+	copy.CopyDir(testFixturePath("init-backend-empty"), td)
+	defer os.RemoveAll(td)
+	defer testChdir(t, td)()
+
+	// create our local state
+	orig := &terraform.State{
+		Modules: []*terraform.ModuleState{
+			{
+				Path: []string{"root"},
+				Outputs: map[string]*terraform.OutputState{
+					"foo": {
+						Value: "bar",
+						Type:  "string",
+					},
+				},
+			},
+		},
+	}
+
+	err := (&state.LocalState{Path: DefaultStateFilename}).WriteState(orig)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	m := testMetaBackend(t, nil)
+	m.forceInitCopy = true
+	// init the backend
+	_, err = m.Backend(&BackendOpts{
+		Init: true,
+	})
+	if err != nil {
+		t.Fatalf("bad: %s", err)
+	}
+
+	// check that we can read the state
+	s := testStateRead(t, DefaultStateFilename)
+	if s.Empty() {
+		t.Fatal("our state was deleted")
+	}
+}
+
 // move options from config to -backend-config
 func TestMetaBackend_configToExtra(t *testing.T) {
 	// Create a temporary working directory that is empty