Allow launch configuration names to be computed

This allows you to set lifecycle create_before_destroy = true
and fixes #532 as then we'll make a new launch config, change
the launch config on the ASG, and *then* delete the old launch
config.

Also tried adding tests which unfortunately don't seem to fail...

builtin/providers/aws/resource_aws_launch_configuration.go

@@ -24,7 +24,8 @@ func resourceAwsLaunchConfiguration() *schema.Resource {
 		Schema: map[string]*schema.Schema{
 			"name": &schema.Schema{
 				Type:     schema.TypeString,
-				Required: true,
+				Optional: true,
+				Computed: true,
 				ForceNew: true,
 			},
 
@@ -122,13 +123,23 @@ func resourceAwsLaunchConfigurationCreate(d *schema.ResourceData, meta interface
 			v.(*schema.Set).List())
 	}
 
+	if v, ok := d.GetOk("name"); ok {
+		createLaunchConfigurationOpts.LaunchConfigurationName = aws.String(v.(string))
+		d.SetId(d.Get("name").(string))
+	} else {
+		hash := sha1.Sum([]byte(fmt.Sprintf("%#v", createLaunchConfigurationOpts)))
+		config_name := fmt.Sprintf("terraform-%s", base64.URLEncoding.EncodeToString(hash[:]))
+		log.Printf("[DEBUG] Computed Launch config name: %s", config_name)
+		createLaunchConfigurationOpts.LaunchConfigurationName = aws.String(config_name)
+		d.SetId(config_name)
+	}
+
 	log.Printf("[DEBUG] autoscaling create launch configuration: %#v", createLaunchConfigurationOpts)
 	err := autoscalingconn.CreateLaunchConfiguration(&createLaunchConfigurationOpts)
 	if err != nil {
 		return fmt.Errorf("Error creating launch configuration: %s", err)
 	}
 
-	d.SetId(d.Get("name").(string))
 	log.Printf("[INFO] launch configuration ID: %s", d.Id())
 
 	// We put a Retry here since sometimes eventual consistency bites

builtin/providers/aws/resource_aws_launch_configuration_test.go

@@ -45,6 +45,16 @@ func TestAccAWSLaunchConfiguration(t *testing.T) {
 						"aws_launch_configuration.bar", "spot_price", "0.01"),
 				),
 			},
+
+			resource.TestStep{
+				Config: testAccAWSLaunchConfigurationNoNameConfig,
+				Check: resource.ComposeTestCheckFunc(
+					testAccCheckAWSLaunchConfigurationExists("aws_launch_configuration.bar", &conf),
+					testAccCheckAWSLaunchConfigurationAttributes(&conf),
+					resource.TestCheckResourceAttr(
+						"aws_launch_configuration.bar", "name", "terraform-foo"), // FIXME - This should fail?!?!?
+				),
+			},
 		},
 	})
 }
@@ -153,3 +163,12 @@ resource "aws_launch_configuration" "bar" {
   spot_price = "0.01"
 }
 `
+
+const testAccAWSLaunchConfigurationNoNameConfig = `
+resource "aws_launch_configuration" "bar" {
+   image_id = "ami-21f78e12"
+   instance_type = "t1.micro"
+   user_data = "foobar-user-data-change"
+   associate_public_ip_address = false
+}
+`