feat: Add support for local terraform states (#3)

tfexec/terraform.go

@@ -111,6 +111,9 @@ type TerraformCLI interface {
 	// StatePush pushes a given State to remote.
 	StatePush(ctx context.Context, state *State, opts ...string) error
 
+	// StateWriteLocal saves the new state to a local state file.
+	StateWriteLocal(ctx context.Context, state *State) error
+
 	// WorkspaceNew creates a new workspace with name "workspace".
 	WorkspaceNew(ctx context.Context, workspace string, opts ...string) error
 

tfexec/terraform_state_local.go

@@ -0,0 +1,24 @@
+package tfexec
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"path/filepath"
+)
+
+// StateWriteLocal saves the new state to a local state file.
+func (c *terraformCLI) StateWriteLocal(_ context.Context, state *State) error {
+	localStateFile := "terraform.tfstate"
+	path := filepath.Join(c.Dir(), localStateFile)
+	if err := os.WriteFile(path, []byte(state.Bytes()), 0600); err != nil {
+		return fmt.Errorf("failed to write %s: %s", localStateFile, err)
+	}
+
+	tmpState, err := writeTempFile(state.Bytes())
+	defer os.Remove(tmpState.Name())
+	if err != nil {
+		return err
+	}
+	return nil
+}

tfmigrate/migrator.go

@@ -23,7 +23,7 @@ type Migrator interface {
 
 // setupWorkDir is a common helper function to set up work dir and returns the
 // current state and a switch back function.
-func setupWorkDir(ctx context.Context, tf tfexec.TerraformCLI, workspace string, isBackendTerraformCloud bool, backendConfig []string, ignoreLegacyStateInitErr bool) (*tfexec.State, func() error, error) {
+func setupWorkDir(ctx context.Context, tf tfexec.TerraformCLI, workspace string, isBackendTerraformCloud bool, backendConfig []string, ignoreLegacyStateInitErr bool, isLocal bool) (*tfexec.State, func() error, error) {
 	// check if terraform command is available.
 	version, err := tf.Version(ctx)
 	if err != nil {
@@ -68,11 +68,18 @@ func setupWorkDir(ctx context.Context, tf tfexec.TerraformCLI, workspace string,
 	if err != nil {
 		return nil, nil, err
 	}
-	// override backend to local
-	log.Printf("[INFO] [migrator@%s] override backend to local\n", tf.Dir())
-	switchBackToRemoteFunc, err := tf.OverrideBackendToLocal(ctx, "_tfmigrate_override.tf", workspace, isBackendTerraformCloud, backendConfig, ignoreLegacyStateInitErr)
-	if err != nil {
-		return nil, nil, err
+	if !isLocal {
+		// override backend to local
+		log.Printf("[INFO] [migrator@%s] override backend to local\n", tf.Dir())
+		switchBackToRemoteFunc, err := tf.OverrideBackendToLocal(ctx, "_tfmigrate_override.tf", workspace, isBackendTerraformCloud, backendConfig, ignoreLegacyStateInitErr)
+		if err != nil {
+			return nil, nil, err
+		}
+		return currentState, switchBackToRemoteFunc, nil
+	}
+	switchBackToRemoteFunc := func() error {
+		log.Printf("[INFO] [executor@%s] nothing to override\n", tf.Dir())
+		return nil
 	}
 	return currentState, switchBackToRemoteFunc, nil
 }

tfmigrate/multi_state_migrator.go

@@ -17,11 +17,15 @@ type MultiStateMigratorConfig struct {
 	// FromSkipPlan controls whether or not to run and analyze Terraform plan
 	// within the from_dir.
 	FromSkipPlan bool `hcl:"from_skip_plan,optional"`
+	// FromIsLocal controls whether or not fromDir is a local state.
+	FromIsLocal bool `hcl:"from_is_local,optional"`
 	// ToDir is a working directory where states of resources move to.
 	ToDir string `hcl:"to_dir"`
 	// ToSkipPlan controls whether or not to run and analyze Terraform plan
 	// within the to_dir.
 	ToSkipPlan bool `hcl:"to_skip_plan,optional"`
+	// ToIsLocal controls whether or not toDir is a local state.
+	ToIsLocal bool `hcl:"to_is_local,optional"`
 	// FromWorkspace is a workspace within FromDir
 	FromWorkspace string `hcl:"from_workspace,optional"`
 	// ToWorkspace is a workspace within ToDir
@@ -63,7 +67,7 @@ func (c *MultiStateMigratorConfig) NewMigrator(o *MigratorOption) (Migrator, err
 		c.ToWorkspace = "default"
 	}
 
-	return NewMultiStateMigrator(c.FromDir, c.ToDir, c.FromWorkspace, c.ToWorkspace, actions, o, c.Force, c.FromSkipPlan, c.ToSkipPlan), nil
+	return NewMultiStateMigrator(c.FromDir, c.ToDir, c.FromWorkspace, c.ToWorkspace, actions, o, c.Force, c.FromSkipPlan, c.ToSkipPlan, c.FromIsLocal, c.ToIsLocal), nil
 }
 
 // MultiStateMigrator implements the Migrator interface.
@@ -72,10 +76,14 @@ type MultiStateMigrator struct {
 	fromTf tfexec.TerraformCLI
 	// fromSkipPlan disables the running of Terraform plan in fromDir.
 	fromSkipPlan bool
+	// fromIsLocal is true if fromDir is a local state.
+	fromIsLocal bool
 	// fromTf is an instance of TerraformCLI which executes terraform command in a toDir.
 	toTf tfexec.TerraformCLI
 	// toSkipPlan disables the running of Terraform plan in toDir.
 	toSkipPlan bool
+	// toIsLocal is true if toDir is a local state.
+	toIsLocal bool
 	//fromWorkspace is the workspace from which the resource will be migrated
 	fromWorkspace string
 	//toWorkspace is the workspace to which the resource will be migrated
@@ -93,7 +101,7 @@ var _ Migrator = (*MultiStateMigrator)(nil)
 
 // NewMultiStateMigrator returns a new MultiStateMigrator instance.
 func NewMultiStateMigrator(fromDir string, toDir string, fromWorkspace string, toWorkspace string,
-	actions []MultiStateAction, o *MigratorOption, force bool, fromSkipPlan bool, toSkipPlan bool) *MultiStateMigrator {
+	actions []MultiStateAction, o *MigratorOption, force bool, fromSkipPlan bool, toSkipPlan bool, fromIsLocal bool, toIsLocal bool) *MultiStateMigrator {
 	fromTf := tfexec.NewTerraformCLI(tfexec.NewExecutor(fromDir, os.Environ()))
 	toTf := tfexec.NewTerraformCLI(tfexec.NewExecutor(toDir, os.Environ()))
 	if o != nil && len(o.ExecPath) > 0 {
@@ -104,8 +112,10 @@ func NewMultiStateMigrator(fromDir string, toDir string, fromWorkspace string, t
 	return &MultiStateMigrator{
 		fromTf:        fromTf,
 		fromSkipPlan:  fromSkipPlan,
+		fromIsLocal:   fromIsLocal,
 		toTf:          toTf,
 		toSkipPlan:    toSkipPlan,
+		toIsLocal:     toIsLocal,
 		fromWorkspace: fromWorkspace,
 		toWorkspace:   toWorkspace,
 		actions:       actions,
@@ -120,7 +130,7 @@ func NewMultiStateMigrator(fromDir string, toDir string, fromWorkspace string, t
 // the Migrator interface between a single and multi state migrator.
 func (m *MultiStateMigrator) plan(ctx context.Context) (fromCurrentState *tfexec.State, toCurrentState *tfexec.State, err error) {
 	// setup fromDir.
-	fromCurrentState, fromSwitchBackToRemoteFunc, err := setupWorkDir(ctx, m.fromTf, m.fromWorkspace, m.o.IsBackendTerraformCloud, m.o.BackendConfig, false)
+	fromCurrentState, fromSwitchBackToRemoteFunc, err := setupWorkDir(ctx, m.fromTf, m.fromWorkspace, m.o.IsBackendTerraformCloud, m.o.BackendConfig, false, m.fromIsLocal)
 	if err != nil {
 		return nil, nil, err
 	}
@@ -130,7 +140,7 @@ func (m *MultiStateMigrator) plan(ctx context.Context) (fromCurrentState *tfexec
 	}()
 
 	// setup toDir.
-	toCurrentState, toSwitchBackToRemoteFunc, err := setupWorkDir(ctx, m.toTf, m.toWorkspace, m.o.IsBackendTerraformCloud, m.o.BackendConfig, false)
+	toCurrentState, toSwitchBackToRemoteFunc, err := setupWorkDir(ctx, m.toTf, m.toWorkspace, m.o.IsBackendTerraformCloud, m.o.BackendConfig, false, m.toIsLocal)
 	if err != nil {
 		return nil, nil, err
 	}
@@ -231,15 +241,31 @@ func (m *MultiStateMigrator) Apply(ctx context.Context) error {
 	// We push toState before fromState, because when moving resources across
 	// states, write them to new state first and then remove them from old one.
 	log.Printf("[INFO] [migrator] start multi state migrator apply phase\n")
-	log.Printf("[INFO] [migrator@%s] push the new state to remote\n", m.toTf.Dir())
-	err = m.toTf.StatePush(ctx, toState)
-	if err != nil {
-		return err
+	if m.toIsLocal {
+		log.Printf("[INFO] [migrator@%s] save the new local state \n", m.toTf.Dir())
+		err = m.toTf.StateWriteLocal(ctx, toState)
+		if err != nil {
+			return err
+		}
+	} else {
+		log.Printf("[INFO] [migrator@%s] push the new state to remote\n", m.toTf.Dir())
+		err = m.toTf.StatePush(ctx, toState)
+		if err != nil {
+			return err
+		}
 	}
-	log.Printf("[INFO] [migrator@%s] push the new state to remote\n", m.fromTf.Dir())
-	err = m.fromTf.StatePush(ctx, fromState)
-	if err != nil {
-		return err
+	if m.fromIsLocal {
+		log.Printf("[INFO] [migrator@%s] save the new local state \n", m.fromTf.Dir())
+		err = m.fromTf.StateWriteLocal(ctx, fromState)
+		if err != nil {
+			return err
+		}
+	} else {
+		log.Printf("[INFO] [migrator@%s] push the new state to remote\n", m.fromTf.Dir())
+		err = m.fromTf.StatePush(ctx, fromState)
+		if err != nil {
+			return err
+		}
 	}
 	log.Printf("[INFO] [migrator] multi state migrator apply success!\n")
 	return nil

tfmigrate/multi_state_migrator_test.go

@@ -218,7 +218,7 @@ resource "null_resource" "qux" {}
 	}
 	o := &MigratorOption{}
 	force := false
-	m := NewMultiStateMigrator(fromTf.Dir(), toTf.Dir(), fromWorkspace, toWorkspace, actions, o, force, false, false)
+	m := NewMultiStateMigrator(fromTf.Dir(), toTf.Dir(), fromWorkspace, toWorkspace, actions, o, force, false, false, false, false)
 	err = m.Plan(ctx)
 	if err != nil {
 		t.Fatalf("failed to run migrator plan: %s", err)
@@ -331,7 +331,7 @@ resource "null_resource" "qux" {}
 	}
 	o := &MigratorOption{}
 	force := false
-	m := NewMultiStateMigrator(fromTf.Dir(), toTf.Dir(), fromWorkspace, toWorkspace, actions, o, force, true, false)
+	m := NewMultiStateMigrator(fromTf.Dir(), toTf.Dir(), fromWorkspace, toWorkspace, actions, o, force, true, false, false, false)
 	err = m.Plan(ctx)
 	if err != nil {
 		t.Fatalf("failed to run migrator plan: %s", err)
@@ -442,7 +442,7 @@ resource "null_resource" "baz" {}
 	}
 	o := &MigratorOption{}
 	force := false
-	m := NewMultiStateMigrator(fromTf.Dir(), toTf.Dir(), fromWorkspace, toWorkspace, actions, o, force, false, true)
+	m := NewMultiStateMigrator(fromTf.Dir(), toTf.Dir(), fromWorkspace, toWorkspace, actions, o, force, false, true, false, false)
 	err = m.Plan(ctx)
 	if err != nil {
 		t.Fatalf("failed to run migrator plan: %s", err)
@@ -552,7 +552,7 @@ resource "null_resource" "qux" {}
 	}
 	o := &MigratorOption{}
 	force := false
-	m := NewMultiStateMigrator(fromTf.Dir(), toTf.Dir(), fromWorkspace, toWorkspace, actions, o, force, true, true)
+	m := NewMultiStateMigrator(fromTf.Dir(), toTf.Dir(), fromWorkspace, toWorkspace, actions, o, force, true, true, false, false)
 	err = m.Plan(ctx)
 	if err != nil {
 		t.Fatalf("failed to run migrator plan: %s", err)
@@ -666,7 +666,7 @@ resource "null_resource" "qux" {}
 	}
 	o := &MigratorOption{}
 	force := false
-	m := NewMultiStateMigrator(fromTf.Dir(), toTf.Dir(), fromWorkspace, toWorkspace, actions, o, force, false, false)
+	m := NewMultiStateMigrator(fromTf.Dir(), toTf.Dir(), fromWorkspace, toWorkspace, actions, o, force, false, false, false, false)
 	err = m.Plan(ctx)
 	if err != nil {
 		t.Fatalf("failed to run migrator plan: %s", err)
@@ -785,7 +785,7 @@ resource "null_resource" "qux2" {}
 	o := &MigratorOption{}
 	o.PlanOut = "foo.tfplan"
 	force := true
-	m := NewMultiStateMigrator(fromTf.Dir(), toTf.Dir(), fromWorkspace, toWorkspace, actions, o, force, false, false)
+	m := NewMultiStateMigrator(fromTf.Dir(), toTf.Dir(), fromWorkspace, toWorkspace, actions, o, force, false, false, false, false)
 	err = m.Plan(ctx)
 	if err != nil {
 		t.Fatalf("failed to run migrator plan: %s", err)
@@ -1003,7 +1003,7 @@ resource "null_resource" "qux" {}
 	}
 	o := &MigratorOption{}
 	force := false
-	m := NewMultiStateMigrator(fromTf.Dir(), toTf.Dir(), fromWorkspace, toWorkspace, actions, o, force, false, false)
+	m := NewMultiStateMigrator(fromTf.Dir(), toTf.Dir(), fromWorkspace, toWorkspace, actions, o, force, false, false, false, false)
 
 	err := m.Plan(ctx)
 	if err == nil {
@@ -1058,7 +1058,7 @@ resource "null_resource" "qux" {}
 	}
 	o := &MigratorOption{}
 	force := false
-	m := NewMultiStateMigrator(fromTf.Dir(), toTf.Dir(), fromWorkspace, toWorkspace, actions, o, force, false, false)
+	m := NewMultiStateMigrator(fromTf.Dir(), toTf.Dir(), fromWorkspace, toWorkspace, actions, o, force, false, false, false, false)
 
 	err := m.Plan(ctx)
 	if err == nil {
@@ -1118,7 +1118,7 @@ resource "null_resource" "qux" {}
 	}
 	o := &MigratorOption{}
 	force := false
-	m := NewMultiStateMigrator(fromTf.Dir(), toTf.Dir(), fromWorkspace, toWorkspace, actions, o, force, false, false)
+	m := NewMultiStateMigrator(fromTf.Dir(), toTf.Dir(), fromWorkspace, toWorkspace, actions, o, force, false, false, false, false)
 
 	err := m.Plan(ctx)
 	if err == nil {

tfmigrate/multi_state_mv_action_test.go

@@ -64,7 +64,7 @@ resource "null_resource" "qux" {}
 	}
 	o := &MigratorOption{}
 	force := false
-	m := NewMultiStateMigrator(fromTf.Dir(), toTf.Dir(), fromWorkspace, toWorkspace, actions, o, force, false, false)
+	m := NewMultiStateMigrator(fromTf.Dir(), toTf.Dir(), fromWorkspace, toWorkspace, actions, o, force, false, false, false, false)
 	err = m.Plan(ctx)
 	if err != nil {
 		t.Fatalf("failed to run migrator plan: %s", err)

tfmigrate/multi_state_xmv_action_test.go

@@ -63,7 +63,7 @@ resource "null_resource" "qux" {}
 	}
 	o := &MigratorOption{}
 	force := false
-	m := NewMultiStateMigrator(fromTf.Dir(), toTf.Dir(), fromWorkspace, toWorkspace, actions, o, force, false, false)
+	m := NewMultiStateMigrator(fromTf.Dir(), toTf.Dir(), fromWorkspace, toWorkspace, actions, o, force, false, false, false, false)
 	err = m.Plan(ctx)
 	if err != nil {
 		t.Fatalf("failed to run migrator plan: %s", err)

tfmigrate/state_migrator.go

@@ -123,7 +123,8 @@ func (m *StateMigrator) plan(ctx context.Context) (currentState *tfexec.State, e
 	}
 
 	// setup work dir.
-	currentState, switchBackToRemoteFunc, err := setupWorkDir(ctx, m.tf, m.workspace, m.o.IsBackendTerraformCloud, m.o.BackendConfig, ignoreLegacyStateInitErr)
+	// TODO: implement isLocal support
+	currentState, switchBackToRemoteFunc, err := setupWorkDir(ctx, m.tf, m.workspace, m.o.IsBackendTerraformCloud, m.o.BackendConfig, ignoreLegacyStateInitErr, false)
 	if err != nil {
 		return nil, err
 	}