command/show: show default state with no args [GH-349]

CHANGELOG.md

@@ -30,6 +30,7 @@ IMPROVEMENTS:
   * config: Trailing commas are now allowed for the final elements of lists.
   * core: Plugins are loaded from `~/.terraform.d/plugins` (Unix) or
     `%USERDATA%/terraform.d/plugins` (Windows).
+  * command/show: With no arguments, it will show the default state. [GH-349]
   * helper/schema: Can now have default values. [GH-245]
   * providers/aws: Tag support for most resources.
   * providers/aws: New resource `db_subnet_group`. [GH-295]

command/show.go

@@ -28,14 +28,27 @@ func (c *ShowCommand) Run(args []string) int {
 	}
 
 	args = cmdFlags.Args()
-	if len(args) != 1 {
+	if len(args) > 1 {
 		c.Ui.Error(
-			"The show command expects exactly one argument with the path\n" +
+			"The show command expects at most one argument with the path\n" +
 				"to a Terraform state or plan file.\n")
 		cmdFlags.Usage()
 		return 1
 	}
-	path := args[0]
+
+	var path string
+	if len(args) > 0 {
+		path = args[0]
+	} else {
+		// We should use the default state if it exists.
+		path = DefaultStateFilename
+		if _, err := os.Stat(DefaultStateFilename); err != nil {
+			if os.IsNotExist(err) {
+				c.Ui.Output("No state.")
+				return 0
+			}
+		}
+	}
 
 	var plan *terraform.Plan
 	var state *terraform.State

command/show_test.go

@@ -1,6 +1,9 @@
 package command
 
 import (
+	"io/ioutil"
+	"os"
+	"path/filepath"
 	"testing"
 
 	"github.com/hashicorp/terraform/config/module"
@@ -27,6 +30,33 @@ func TestShow(t *testing.T) {
 }
 
 func TestShow_noArgs(t *testing.T) {
+	// Create the default state
+	td, err := ioutil.TempDir("", "tf")
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+	statePath := filepath.Join(td, DefaultStateFilename)
+
+	f, err := os.Create(statePath)
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+	err = terraform.WriteState(testState(), f)
+	f.Close()
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	// Change to the temporary directory
+	cwd, err := os.Getwd()
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+	if err := os.Chdir(filepath.Dir(statePath)); err != nil {
+		t.Fatalf("err: %s", err)
+	}
+	defer os.Chdir(cwd)
+
 	ui := new(cli.MockUi)
 	c := &ShowCommand{
 		Meta: Meta{
@@ -36,7 +66,39 @@ func TestShow_noArgs(t *testing.T) {
 	}
 
 	args := []string{}
-	if code := c.Run(args); code != 1 {
+	if code := c.Run(args); code != 0 {
+		t.Fatalf("bad: \n%s", ui.OutputWriter.String())
+	}
+}
+
+func TestShow_noArgsNoState(t *testing.T) {
+	// Create the default state
+	td, err := ioutil.TempDir("", "tf")
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+	statePath := filepath.Join(td, DefaultStateFilename)
+
+	// Change to the temporary directory
+	cwd, err := os.Getwd()
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+	if err := os.Chdir(filepath.Dir(statePath)); err != nil {
+		t.Fatalf("err: %s", err)
+	}
+	defer os.Chdir(cwd)
+
+	ui := new(cli.MockUi)
+	c := &ShowCommand{
+		Meta: Meta{
+			ContextOpts: testCtxConfig(testProvider()),
+			Ui:          ui,
+		},
+	}
+
+	args := []string{}
+	if code := c.Run(args); code != 0 {
 		t.Fatalf("bad: \n%s", ui.OutputWriter.String())
 	}
 }