refactor: don't read lock.json,config.toml in subcmd package

See _docs/json-dsl.md for layered architecture:

1. (Gateway layer): pass subcommand arguments, lock.json & config.toml
   structure to Subcmd layer
2. (Subcmd layer): Create an AST according to given information
    * This layer cannot touch filesystem, because it makes unit testing
    difficult

Author: tyru

subcmd/cmd.go renamed to gateway/gateway.go

@@ -1,90 +1,84 @@
-package subcmd
+package gateway
 
 import (
 	"errors"
-	"flag"
 	"os"
 	"os/user"
 	"runtime"
 
 	"github.com/vim-volt/volt/config"
+	"github.com/vim-volt/volt/lockjson"
 	"github.com/vim-volt/volt/logger"
+	"github.com/vim-volt/volt/subcmd"
 )
 
-var cmdMap = make(map[string]Cmd)
-
-// Cmd represents volt's subcommand interface.
-// All subcommands must implement this.
-type Cmd interface {
-	ProhibitRootExecution(args []string) bool
-	Run(args []string) *Error
-	FlagSet() *flag.FlagSet
-}
-
 // RunnerFunc invokes c with args.
 // On unit testing, a mock function was given.
-type RunnerFunc func(c Cmd, args []string) *Error
-
-// Error is a command error.
-// It also has a exit code.
-type Error struct {
-	Code int
-	Msg  string
-}
-
-func (e *Error) Error() string {
-	return e.Msg
-}
+type RunnerFunc func(c subcmd.Cmd, runctx *subcmd.RunContext) *subcmd.Error
 
 // DefaultRunner simply runs command with args
-func DefaultRunner(c Cmd, args []string) *Error {
-	return c.Run(args)
+func DefaultRunner(c subcmd.Cmd, runctx *subcmd.RunContext) *subcmd.Error {
+	return c.Run(runctx)
 }
 
 // Run is invoked by main(), each argument means 'volt {subcmd} {args}'.
-func Run(args []string, cont RunnerFunc) *Error {
+func Run(args []string, cont RunnerFunc) *subcmd.Error {
 	if os.Getenv("VOLT_DEBUG") != "" {
 		logger.SetLevel(logger.DebugLevel)
 	}
 
 	if len(args) <= 1 {
 		args = append(args, "help")
 	}
-	subCmd := args[1]
+	cmdname := args[1]
 	args = args[2:]
 
+	// Read config.toml
+	cfg, err := config.Read()
+	if err != nil {
+		err = errors.New("could not read config.toml: " + err.Error())
+		return &subcmd.Error{Code: 2, Msg: err.Error()}
+	}
+
 	// Expand subcommand alias
-	subCmd, args, err := expandAlias(subCmd, args)
+	cmdname, args, err = expandAlias(cmdname, args, cfg)
 	if err != nil {
-		return &Error{Code: 1, Msg: err.Error()}
+		return &subcmd.Error{Code: 1, Msg: err.Error()}
 	}
 
-	c, exists := cmdMap[subCmd]
+	c, exists := subcmd.LookupSubcmd(cmdname)
 	if !exists {
-		return &Error{Code: 3, Msg: "Unknown command '" + subCmd + "'"}
+		return &subcmd.Error{Code: 3, Msg: "Unknown command '" + cmdname + "'"}
 	}
 
 	// Disallow executing the commands which may modify files in root priviledge
 	if c.ProhibitRootExecution(args) {
 		err := detectPriviledgedUser()
 		if err != nil {
-			return &Error{Code: 4, Msg: err.Error()}
+			return &subcmd.Error{Code: 4, Msg: err.Error()}
 		}
 	}
 
-	return cont(c, args)
-}
-
-func expandAlias(subCmd string, args []string) (string, []string, error) {
-	cfg, err := config.Read()
+	// Read lock.json
+	lockJSON, err := lockjson.Read()
 	if err != nil {
-		return "", nil, errors.New("could not read config.toml: " + err.Error())
+		err = errors.New("failed to read lock.json: " + err.Error())
+		return &subcmd.Error{Code: 5, Msg: err.Error()}
 	}
-	if newArgs, exists := cfg.Alias[subCmd]; exists && len(newArgs) > 0 {
-		subCmd = newArgs[0]
+
+	return cont(c, &subcmd.RunContext{
+		Args:     args,
+		LockJSON: lockJSON,
+		Config:   cfg,
+	})
+}
+
+func expandAlias(cmdname string, args []string, cfg *config.Config) (string, []string, error) {
+	if newArgs, exists := cfg.Alias[cmdname]; exists && len(newArgs) > 0 {
+		cmdname = newArgs[0]
 		args = append(newArgs[1:], args...)
 	}
-	return subCmd, args, nil
+	return cmdname, args, nil
 }
 
 // On Windows, this function always returns nil.

main.go

@@ -5,12 +5,12 @@ package main
 import (
 	"os"
 
+	"github.com/vim-volt/volt/gateway"
 	"github.com/vim-volt/volt/logger"
-	"github.com/vim-volt/volt/subcmd"
 )
 
 func main() {
-	err := subcmd.Run(os.Args, subcmd.DefaultRunner)
+	err := gateway.Run(os.Args, gateway.DefaultRunner)
 	if err != nil {
 		logger.Error(err.Msg)
 		os.Exit(err.Code)

migration/lockjson.go

@@ -3,6 +3,7 @@ package migration
 import (
 	"errors"
 
+	"github.com/vim-volt/volt/config"
 	"github.com/vim-volt/volt/lockjson"
 	"github.com/vim-volt/volt/transaction"
 )
@@ -31,15 +32,9 @@ Description
   To suppress this, running this command simply reads and writes migrated structure to lock.json.`
 }
 
-func (*lockjsonMigrater) Migrate() error {
-	// Read lock.json
-	lockJSON, err := lockjson.ReadNoMigrationMsg()
-	if err != nil {
-		return errors.New("could not read lock.json: " + err.Error())
-	}
-
+func (*lockjsonMigrater) Migrate(lockJSON *lockjson.LockJSON, cfg *config.Config) error {
 	// Begin transaction
-	err = transaction.Create()
+	err := transaction.Create()
 	if err != nil {
 		return err
 	}

migration/migrater.go

@@ -3,11 +3,14 @@ package migration
 import (
 	"errors"
 	"sort"
+
+	"github.com/vim-volt/volt/config"
+	"github.com/vim-volt/volt/lockjson"
 )
 
 // Migrater migrates many kinds of data.
 type Migrater interface {
-	Migrate() error
+	Migrate(*lockjson.LockJSON, *config.Config) error
 	Name() string
 	Description(brief bool) string
 }

migration/plugconf-config-func.go

@@ -7,6 +7,7 @@ import (
 	"path/filepath"
 	"strings"
 
+	"github.com/vim-volt/volt/config"
 	"github.com/vim-volt/volt/lockjson"
 	"github.com/vim-volt/volt/logger"
 	"github.com/vim-volt/volt/pathutil"
@@ -39,13 +40,7 @@ Description
   All plugconf files are replaced with new contents.`
 }
 
-func (*plugconfConfigMigrater) Migrate() error {
-	// Read lock.json
-	lockJSON, err := lockjson.ReadNoMigrationMsg()
-	if err != nil {
-		return errors.New("could not read lock.json: " + err.Error())
-	}
-
+func (*plugconfConfigMigrater) Migrate(lockJSON *lockjson.LockJSON, cfg *config.Config) error {
 	results, parseErr := plugconf.ParseMultiPlugconf(lockJSON.Repos)
 	if parseErr.HasErrs() {
 		logger.Error("Please fix the following errors before migration:")
@@ -82,21 +77,21 @@ func (*plugconfConfigMigrater) Migrate() error {
 	// After checking errors, write the content to files
 	for _, info := range infoList {
 		os.MkdirAll(filepath.Dir(info.path), 0755)
-		err = ioutil.WriteFile(info.path, info.content, 0644)
+		err := ioutil.WriteFile(info.path, info.content, 0644)
 		if err != nil {
 			return err
 		}
 	}
 
 	// Begin transaction
-	err = transaction.Create()
+	err := transaction.Create()
 	if err != nil {
 		return err
 	}
 	defer transaction.Remove()
 
 	// Build ~/.vim/pack/volt dir
-	err = builder.Build(false)
+	err = builder.Build(false, lockJSON, cfg)
 	if err != nil {
 		return errors.New("could not build " + pathutil.VimVoltDir() + ": " + err.Error())
 	}

subcmd/build.go

@@ -53,10 +53,10 @@ Description
 	return fs
 }
 
-func (cmd *buildCmd) Run(args []string) *Error {
+func (cmd *buildCmd) Run(runctx *RunContext) *Error {
 	// Parse args
 	fs := cmd.FlagSet()
-	fs.Parse(args)
+	fs.Parse(runctx.Args)
 	if cmd.helped {
 		return nil
 	}
@@ -69,7 +69,7 @@ func (cmd *buildCmd) Run(args []string) *Error {
 	}
 	defer transaction.Remove()
 
-	err = builder.Build(cmd.full)
+	err = builder.Build(cmd.full, runctx.LockJSON, runctx.Config)
 	if err != nil {
 		logger.Error()
 		return &Error{Code: 12, Msg: "Failed to build: " + err.Error()}

subcmd/builder/base.go

@@ -18,7 +18,9 @@ import (
 )
 
 // BaseBuilder is a base struct which all builders must implement
-type BaseBuilder struct{}
+type BaseBuilder struct {
+	lockJSON *lockjson.LockJSON
+}
 
 func (builder *BaseBuilder) installVimrcAndGvimrc(profileName, vimrcPath, gvimrcPath string) error {
 	// Save old vimrc file as {vimrc}.bak

subcmd/builder/builder.go

@@ -6,6 +6,7 @@ import (
 
 	"github.com/vim-volt/volt/buildinfo"
 	"github.com/vim-volt/volt/config"
+	"github.com/vim-volt/volt/lockjson"
 	"github.com/vim-volt/volt/logger"
 	"github.com/vim-volt/volt/pathutil"
 )
@@ -18,15 +19,9 @@ type Builder interface {
 const currentBuildInfoVersion = 2
 
 // Build creates/updates ~/.vim/pack/volt directory
-func Build(full bool) error {
-	// Read config.toml
-	cfg, err := config.Read()
-	if err != nil {
-		return errors.New("could not read config.toml: " + err.Error())
-	}
-
+func Build(full bool, lockJSON *lockjson.LockJSON, cfg *config.Config) error {
 	// Get builder
-	blder, err := getBuilder(cfg.Build.Strategy)
+	blder, err := getBuilder(cfg.Build.Strategy, lockJSON)
 	if err != nil {
 		return err
 	}
@@ -78,12 +73,13 @@ func Build(full bool) error {
 	return blder.Build(buildInfo, buildReposMap)
 }
 
-func getBuilder(strategy string) (Builder, error) {
+func getBuilder(strategy string, lockJSON *lockjson.LockJSON) (Builder, error) {
+	base := &BaseBuilder{lockJSON: lockJSON}
 	switch strategy {
 	case config.SymlinkBuilder:
-		return &symlinkBuilder{}, nil
+		return &symlinkBuilder{base}, nil
 	case config.CopyBuilder:
-		return &copyBuilder{}, nil
+		return &copyBuilder{base}, nil
 	default:
 		return nil, errors.New("unknown builder type: " + strategy)
 	}

subcmd/builder/copy.go

@@ -22,7 +22,7 @@ import (
 )
 
 type copyBuilder struct {
-	BaseBuilder
+	*BaseBuilder
 }
 
 func (builder *copyBuilder) Build(buildInfo *buildinfo.BuildInfo, buildReposMap map[pathutil.ReposPath]*buildinfo.Repos) error {
@@ -32,14 +32,8 @@ func (builder *copyBuilder) Build(buildInfo *buildinfo.BuildInfo, buildReposMap
 		return err
 	}
 
-	// Read lock.json
-	lockJSON, err := lockjson.Read()
-	if err != nil {
-		return errors.New("could not read lock.json: " + err.Error())
-	}
-
 	// Get current profile's repos list
-	reposList, err := lockJSON.GetCurrentReposList()
+	reposList, err := builder.lockJSON.GetCurrentReposList()
 	if err != nil {
 		return err
 	}
@@ -50,7 +44,7 @@ func (builder *copyBuilder) Build(buildInfo *buildinfo.BuildInfo, buildReposMap
 	vimrcPath := filepath.Join(vimDir, pathutil.Vimrc)
 	gvimrcPath := filepath.Join(vimDir, pathutil.Gvimrc)
 	err = builder.installVimrcAndGvimrc(
-		lockJSON.CurrentProfileName, vimrcPath, gvimrcPath,
+		builder.lockJSON.CurrentProfileName, vimrcPath, gvimrcPath,
 	)
 	if err != nil {
 		return err
@@ -98,7 +92,7 @@ func (builder *copyBuilder) Build(buildInfo *buildinfo.BuildInfo, buildReposMap
 	}
 
 	// Write bundled plugconf file
-	rcDir := pathutil.RCDir(lockJSON.CurrentProfileName)
+	rcDir := pathutil.RCDir(builder.lockJSON.CurrentProfileName)
 	vimrc := ""
 	if path := filepath.Join(rcDir, pathutil.ProfileVimrc); pathutil.Exists(path) {
 		vimrc = path

subcmd/builder/symlink.go

@@ -20,7 +20,7 @@ import (
 )
 
 type symlinkBuilder struct {
-	BaseBuilder
+	*BaseBuilder
 }
 
 // TODO: rollback when return err (!= nil)
@@ -31,11 +31,7 @@ func (builder *symlinkBuilder) Build(buildInfo *buildinfo.BuildInfo, buildReposM
 	}
 
 	// Get current profile's repos list
-	lockJSON, err := lockjson.Read()
-	if err != nil {
-		return errors.New("could not read lock.json: " + err.Error())
-	}
-	reposList, err := lockJSON.GetCurrentReposList()
+	reposList, err := builder.lockJSON.GetCurrentReposList()
 	if err != nil {
 		return err
 	}
@@ -46,7 +42,7 @@ func (builder *symlinkBuilder) Build(buildInfo *buildinfo.BuildInfo, buildReposM
 	vimrcPath := filepath.Join(vimDir, pathutil.Vimrc)
 	gvimrcPath := filepath.Join(vimDir, pathutil.Gvimrc)
 	err = builder.installVimrcAndGvimrc(
-		lockJSON.CurrentProfileName, vimrcPath, gvimrcPath,
+		builder.lockJSON.CurrentProfileName, vimrcPath, gvimrcPath,
 	)
 	if err != nil {
 		return err
@@ -86,7 +82,7 @@ func (builder *symlinkBuilder) Build(buildInfo *buildinfo.BuildInfo, buildReposM
 	}
 
 	// Write bundled plugconf file
-	rcDir := pathutil.RCDir(lockJSON.CurrentProfileName)
+	rcDir := pathutil.RCDir(builder.lockJSON.CurrentProfileName)
 	vimrc := ""
 	if path := filepath.Join(rcDir, pathutil.ProfileVimrc); pathutil.Exists(path) {
 		vimrc = path