Add plugin dir scaffolding

add pluginDir to command.Meta, the flag to initialize it, and the
methods to save and restore it.

command/apply.go

@@ -65,6 +65,12 @@ func (c *ApplyCommand) Run(args []string) int {
 		return 1
 	}
 
+	// Check for user-supplied plugin path
+	if c.pluginPath, err = c.loadPluginPath(); err != nil {
+		c.Ui.Error(fmt.Sprintf("Error loading plugin path: %s", err))
+		return 1
+	}
+
 	if !c.Destroy && maybeInit {
 		// We need the pwd for the getter operation below
 		pwd, err := os.Getwd()

command/command.go

@@ -15,6 +15,10 @@ var test bool = false
 // DefaultDataDir is the default directory for storing local data.
 const DefaultDataDir = ".terraform"
 
+// PluginPathFile is the name of the file in the data dir which stores the list
+// of directories supplied by the user with the `-plugin-dir` flag during init.
+const PluginPathFile = "plugin_path"
+
 // DefaultPluginVendorDir is the location in the config directory to look for
 // user-added plugin binaries. Terraform only reads from this path if it
 // exists, it is never created by terraform.

command/init.go

@@ -32,6 +32,7 @@ type InitCommand struct {
 func (c *InitCommand) Run(args []string) int {
 	var flagBackend, flagGet, flagGetPlugins, flagUpgrade bool
 	var flagConfigExtra map[string]interface{}
+	var flagPluginPath FlagStringSlice
 
 	args = c.Meta.process(args, false)
 	cmdFlags := c.flagSet("init")
@@ -44,12 +45,15 @@ func (c *InitCommand) Run(args []string) int {
 	cmdFlags.DurationVar(&c.Meta.stateLockTimeout, "lock-timeout", 0, "lock timeout")
 	cmdFlags.BoolVar(&c.reconfigure, "reconfigure", false, "reconfigure")
 	cmdFlags.BoolVar(&flagUpgrade, "upgrade", false, "")
+	cmdFlags.Var(&flagPluginPath, "plugin-dir", "plugin directory")
 
 	cmdFlags.Usage = func() { c.Ui.Error(c.Help()) }
 	if err := cmdFlags.Parse(args); err != nil {
 		return 1
 	}
 
+	c.pluginPath = flagPluginPath
+
 	// set getProvider if we don't have a test version already
 	if c.providerInstaller == nil {
 		c.providerInstaller = &discovery.ProviderInstaller{
@@ -67,6 +71,11 @@ func (c *InitCommand) Run(args []string) int {
 		return 1
 	}
 
+	if err := c.storePluginPath(c.pluginPath); err != nil {
+		c.Ui.Error(fmt.Sprintf("Error saving -plugin-path values: %s", err))
+		return 1
+	}
+
 	// Get our pwd. We don't always need it but always getting it is easier
 	// than the logic to determine if it is or isn't needed.
 	pwd, err := os.Getwd()

command/meta.go

@@ -48,6 +48,12 @@ type Meta struct {
 	// DataDir method.
 	dataDir string
 
+	// pluginPath is a user defined set of directories to look for plugins.
+	// This is set during init with the `-plugin-dir` flag, saved to a file in
+	// the data directory.
+	// This overrides all other search paths when discoverying plugins.
+	pluginPath []string
+
 	// Override certain behavior for tests within this package
 	testingOverrides *testingOverrides
 

command/plan.go

@@ -45,6 +45,12 @@ func (c *PlanCommand) Run(args []string) int {
 		return 1
 	}
 
+	// Check for user-supplied plugin path
+	if c.pluginPath, err = c.loadPluginPath(); err != nil {
+		c.Ui.Error(fmt.Sprintf("Error loading plugin path: %s", err))
+		return 1
+	}
+
 	// Check if the path is a plan
 	plan, err := c.Plan(configPath)
 	if err != nil {

command/plugins.go

@@ -1,8 +1,11 @@
 package command
 
 import (
+	"encoding/json"
 	"fmt"
+	"io/ioutil"
 	"log"
+	"os"
 	"os/exec"
 	"path/filepath"
 	"runtime"
@@ -69,6 +72,40 @@ func (r *multiVersionProviderResolver) ResolveProviders(
 	return factories, errs
 }
 
+// store the user-supplied path for plugin discovery
+func (m *Meta) storePluginPath(pluginPath []string) error {
+	if len(pluginPath) == 0 {
+		return nil
+	}
+
+	js, err := json.MarshalIndent(pluginPath, "", "  ")
+	if err != nil {
+		return err
+	}
+
+	return ioutil.WriteFile(filepath.Join(m.DataDir(), PluginPathFile), js, 0644)
+}
+
+// Load the user-defined plugin search path into Meta.pluginPath if the file
+// exists.
+func (m *Meta) loadPluginPath() ([]string, error) {
+	js, err := ioutil.ReadFile(filepath.Join(m.DataDir(), PluginPathFile))
+	if os.IsNotExist(err) {
+		return nil, nil
+	}
+
+	if err != nil {
+		return nil, err
+	}
+
+	var pluginPath []string
+	if err := json.Unmarshal(js, &pluginPath); err != nil {
+		return nil, err
+	}
+
+	return pluginPath, nil
+}
+
 // the default location for automatically installed plugins
 func (m *Meta) pluginDir() string {
 	return filepath.Join(m.DataDir(), "plugins", fmt.Sprintf("%s_%s", runtime.GOOS, runtime.GOARCH))
@@ -80,6 +117,10 @@ func (m *Meta) pluginDir() string {
 // of the same plugin version are found, but newer versions always override
 // older versions where both satisfy the provider version constraints.
 func (m *Meta) pluginDirs(includeAutoInstalled bool) []string {
+	// user defined paths take precedence
+	if len(m.pluginPath) > 0 {
+		return m.pluginPath
+	}
 
 	// When searching the following directories, earlier entries get precedence
 	// if the same plugin version is found twice, but newer versions will

command/refresh.go

@@ -44,6 +44,12 @@ func (c *RefreshCommand) Run(args []string) int {
 		return 1
 	}
 
+	// Check for user-supplied plugin path
+	if c.pluginPath, err = c.loadPluginPath(); err != nil {
+		c.Ui.Error(fmt.Sprintf("Error loading plugin path: %s", err))
+		return 1
+	}
+
 	var conf *config.Config
 	if mod != nil {
 		conf = mod.Config()