Define a migration file with HCL

config/migration.go

@@ -0,0 +1,144 @@
+package config
+
+import (
+	"fmt"
+
+	"github.com/hashicorp/hcl/v2"
+	"github.com/hashicorp/hcl/v2/gohcl"
+	"github.com/hashicorp/hcl/v2/hclsimple"
+	"github.com/minamijoyo/tfmigrate/tfmigrate"
+)
+
+// MigrationFile represents a config for migration written in HCL.
+type MigrationFile struct {
+	// Migration is a migration block.
+	// It must contain only one block, and multiple blocks are not allowed,
+	// because it's hard to re-run the file if partially failed.
+	Migration MigrationBlock `hcl:"migration,block"`
+}
+
+// MigrationBlock represents a migration block in HCL.
+type MigrationBlock struct {
+	// Type is a type for migration.
+	// Valid values are `state` and `multi_state`.
+	Type string `hcl:"type,label"`
+	// Name is an arbitrary name for migration.
+	Name string `hcl:"name,label"`
+	// Remain is a body of migration block.
+	// We first decode only a block header and then decode schema depending on
+	// its type label.
+	Remain hcl.Body `hcl:",remain"`
+}
+
+// StateMigratorConfig is a config for StateMigrator.
+type StateMigratorConfig struct {
+	// Dir is a working directory for executing terraform command.
+	// Default to `.` (current directory).
+	Dir string `hcl:"dir,optional"`
+	// Actions is a list of state action.
+	// action is a plain text for state operation.
+	// Valid formats are the following.
+	// "mv <source> <destination>"
+	// "rm <addresses>...
+	// "import <address> <id>"
+	// We could define strict block schema for action, but intentionally use a
+	// schema-less string to allow us to easily copy terraform state command to
+	// action.
+	Actions []string `hcl:"actions"`
+}
+
+// MultiStateMigratorConfig is a config for MultiStateMigrator.
+type MultiStateMigratorConfig struct {
+	// FromDir is a working directory where states of resources move from.
+	FromDir string `hcl:"from_dir"`
+	// ToDir is a working directory where states of rsources move to.
+	ToDir string `hcl:"to_dir"`
+	// Actions is a list of multi state action.
+	// action is a plain text for state operation.
+	// Valid formats are the following.
+	// "mv <source> <destination>"
+	Actions []string `hcl:"actions"`
+}
+
+// MigratorConfig is an interface of factory method for Migrator.
+type MigratorConfig interface {
+	// NewMigrator returns a new instance of Migrator.
+	NewMigrator(o *tfmigrate.MigratorOption) (tfmigrate.Migrator, error)
+}
+
+// StateMigratorConfig implements a MigratorConfig.
+var _ MigratorConfig = (*StateMigratorConfig)(nil)
+
+// MultiStateMigratorConfig implements a MigratorConfig.
+var _ MigratorConfig = (*MultiStateMigratorConfig)(nil)
+
+// NewMigrator returns a new instance of StateMigrator.
+func (c *StateMigratorConfig) NewMigrator(o *tfmigrate.MigratorOption) (tfmigrate.Migrator, error) {
+	// default working directory
+	dir := "."
+	if len(c.Dir) > 0 {
+		dir = c.Dir
+	}
+
+	// build actions from config.
+	actions := []tfmigrate.StateAction{}
+	for _, cmdStr := range c.Actions {
+		action, err := tfmigrate.NewStateActionFromString(cmdStr)
+		if err != nil {
+			return nil, err
+		}
+		actions = append(actions, action)
+	}
+
+	return tfmigrate.NewStateMigrator(dir, actions, o), nil
+}
+
+// NewMigrator returns a new instance of MultiStateMigrator.
+func (c *MultiStateMigratorConfig) NewMigrator(o *tfmigrate.MigratorOption) (tfmigrate.Migrator, error) {
+	// build actions from config.
+	actions := []tfmigrate.MultiStateAction{}
+	for _, cmdStr := range c.Actions {
+		action, err := tfmigrate.NewMultiStateActionFromString(cmdStr)
+		if err != nil {
+			return nil, err
+		}
+		actions = append(actions, action)
+	}
+
+	return tfmigrate.NewMultiStateMigrator(c.FromDir, c.ToDir, actions, o), nil
+}
+
+// ParseMigrationFile parses a given source of migration file and returns a MigratorConfig.
+// Note that this method does not read a file and you should pass source of config in bytes.
+// The filename is used for error message and selecting HCL syntax (.hcl and .hcl.json).
+func ParseMigrationFile(filename string, source []byte) (MigratorConfig, error) {
+	// Decode migration block header.
+	var f MigrationFile
+	err := hclsimple.Decode(filename, source, nil, &f)
+	if err != nil {
+		return nil, fmt.Errorf("failed to decode migration file: %s, err: %s", filename, err)
+	}
+
+	// switch schema by migration type.
+	var config MigratorConfig
+	m := f.Migration
+	switch m.Type {
+	case "state":
+		var state StateMigratorConfig
+		diags := gohcl.DecodeBody(m.Remain, nil, &state)
+		if diags.HasErrors() {
+			return nil, diags
+		}
+		config = &state
+	case "multi_state":
+		var multiState MultiStateMigratorConfig
+		diags := gohcl.DecodeBody(m.Remain, nil, &multiState)
+		if diags.HasErrors() {
+			return nil, diags
+		}
+		config = &multiState
+	default:
+		return nil, fmt.Errorf("unknown migration type in %s: %s", filename, m.Type)
+	}
+	return config, nil
+}

config/migration_test.go

@@ -0,0 +1,65 @@
+package config
+
+import (
+	"testing"
+
+	"github.com/davecgh/go-spew/spew"
+	"github.com/minamijoyo/tfmigrate/tfmigrate"
+)
+
+func TestParseMigrationFileWithState(t *testing.T) {
+	const source = `
+	migration "state" "test" {
+	  dir = "dir1"
+		actions = [
+			"mv aws_security_group.foo aws_security_group.foo2",
+			"mv aws_security_group.bar aws_security_group.bar2",
+			"rm aws_security_group.bar",
+			"import aws_security_group.piyo piyo",
+		]
+	}
+	`
+
+	config, err := ParseMigrationFile("test.hcl", []byte(source))
+	if err != nil {
+		t.Fatalf("failed to ParseMigration: %s", err)
+	}
+	spew.Dump(config)
+
+	o := &tfmigrate.MigratorOption{
+		ExecPath: "direnv exec . terraform",
+	}
+	m, err := config.NewMigrator(o)
+	if err != nil {
+		t.Fatalf("failed to NewMigrator: %s", err)
+	}
+	spew.Dump(m)
+}
+
+func TestParseMigrationFileWithMultiState(t *testing.T) {
+	const source = `
+	migration "multi_state" "mv_dir1_dir2" {
+	  from_dir = "dir1"
+	  to_dir   = "dir2"
+		actions = [
+			"mv aws_security_group.foo aws_security_group.foo2",
+			"mv aws_security_group.bar aws_security_group.bar2",
+		]
+	}
+	`
+
+	config, err := ParseMigrationFile("test.hcl", []byte(source))
+	if err != nil {
+		t.Fatalf("failed to ParseMigration: %s", err)
+	}
+	spew.Dump(config)
+
+	o := &tfmigrate.MigratorOption{
+		ExecPath: "direnv exec . terraform",
+	}
+	m, err := config.NewMigrator(o)
+	if err != nil {
+		t.Fatalf("failed to NewMigrator: %s", err)
+	}
+	spew.Dump(m)
+}

go.mod

@@ -4,6 +4,7 @@ go 1.14
 
 require (
 	github.com/davecgh/go-spew v1.1.1
+	github.com/hashicorp/hcl/v2 v2.6.0
 	github.com/hashicorp/logutils v1.0.0
 	github.com/mattn/go-shellwords v1.0.10
 	golang.org/x/lint v0.0.0-20200302205851-738671d3881b

go.sum

@@ -1,20 +1,62 @@
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 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
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+github.com/go-test/deep v1.0.3 h1:ZrJSEWsXzPOxaZnFteGEfooLba+ju3FYIbOrS+rQd68=
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tfmigrate/multi_state_action.go

@@ -0,0 +1,48 @@
+package tfmigrate
+
+import (
+	"context"
+	"fmt"
+	"strings"
+
+	"github.com/minamijoyo/tfmigrate/tfexec"
+)
+
+// MultiStateAction abstracts multi state migration operations.
+// It's used for moving resources from a state to another.
+type MultiStateAction interface {
+	// MultiStateUpdate updates given two states and returns new two states.
+	MultiStateUpdate(ctx context.Context, fromTf tfexec.TerraformCLI, toTf tfexec.TerraformCLI, fromState *tfexec.State, toState *tfexec.State) (*tfexec.State, *tfexec.State, error)
+}
+
+// NewMultiStateActionFromString is a factory method which returns a new
+// MultiStateAction from a given string.
+// cmdStr is a plain text for state operation.
+// This method is useful to build an action from terraform state command.
+// Valid formats are the following.
+// "mv <source> <destination>"
+func NewMultiStateActionFromString(cmdStr string) (MultiStateAction, error) {
+	// split cmdStr using Fields instead of Split to allow cmdStr to have duplicated white spaces.
+	args := strings.Fields(cmdStr)
+	if len(args) == 0 {
+		return nil, fmt.Errorf("multi state action is empty: %s", cmdStr)
+	}
+	actionType := args[0]
+
+	// switch by action type and parse arguments and build an action.
+	var action MultiStateAction
+	switch actionType {
+	case "mv":
+		if len(args) != 3 {
+			return nil, fmt.Errorf("multi state mv action is invalid: %s", cmdStr)
+		}
+		src := args[1]
+		dst := args[2]
+		action = NewMultiStateMvAction(src, dst)
+
+	default:
+		return nil, fmt.Errorf("unknown multi state action type: %s", cmdStr)
+	}
+
+	return action, nil
+}

tfmigrate/multi_state_migrator.go

@@ -8,13 +8,6 @@ import (
 	"github.com/minamijoyo/tfmigrate/tfexec"
 )
 
-// MultiStateAction abstracts multi state migration operations.
-// It's used for moving resources from a state to another.
-type MultiStateAction interface {
-	// MultiStateUpdate updates given two states and returns new two states.
-	MultiStateUpdate(ctx context.Context, fromTf tfexec.TerraformCLI, toTf tfexec.TerraformCLI, fromState *tfexec.State, toState *tfexec.State) (*tfexec.State, *tfexec.State, error)
-}
-
 // MultiStateMigrator implements the Migrator interface.
 type MultiStateMigrator struct {
 	// fromTf is an instance of TerraformCLI which executes terraform command in a fromDir.