Re-allow spot + tenancy. Validate tenancy is set to a usable value

builder/amazon/common/run_config.go

@@ -378,7 +378,9 @@ type RunConfig struct {
 	SubnetId string `mapstructure:"subnet_id" required:"false"`
 	// [Tenancy](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/dedicated-instance.html) used
 	// when Packer launches the EC2 instance, allowing it to be launched on dedicated hardware.
-	// If unset, the default shared tenancy will be used.
+	//
+	// The default is "default", meaning shared tenancy. Allowed values are "default",
+	// "dedicated" and "host".
 	Tenancy string `mapstructure:"tenancy" required:"false"`
 	// The name of the temporary key pair to
 	// generate. By default, Packer generates a name that looks like
@@ -635,10 +637,11 @@ func (c *RunConfig) Prepare(ctx *interpolate.Context) []error {
 		}
 	}
 
-	if c.Tenancy != "" && c.Tenancy != "default" {
-		if c.SpotPrice != "" {
-			errs = append(errs, fmt.Errorf("Error: Non-default tenancy cannot be used in conjunction with Spot Instances"))
-		}
+	if c.Tenancy != "" &&
+		c.Tenancy != "default" &&
+		c.Tenancy != "dedicated" &&
+		c.Tenancy != "host" {
+		errs = append(errs, fmt.Errorf("Error: Unknown tenancy type %s", c.Tenancy))
 	}
 
 	return errs

builder/amazon/common/run_config_test.go

@@ -233,22 +233,22 @@ func TestRunConfigPrepare_TemporaryKeyPairName(t *testing.T) {
 	}
 }
 
-func TestRunConfigPrepare_TenancySpot(t *testing.T) {
+func TestRunConfigPrepare_TenancyBad(t *testing.T) {
 	c := testConfig()
-	c.Tenancy = "dedicated"
-	c.SpotPrice = "1"
+	c.Tenancy = "not_real"
 
 	if err := c.Prepare(nil); len(err) != 1 {
-		t.Fatal("Should error if non-default tenancy and spot price are both set")
+		t.Fatal("Should error if tenancy is set to an invalid type")
 	}
 }
 
-func TestRunConfigPrepare_TenancySpotDefault(t *testing.T) {
-	c := testConfig()
-	c.Tenancy = "default"
-	c.SpotPrice = "1"
-
-	if err := c.Prepare(nil); len(err) != 0 {
-		t.Fatal("Should not error if tenancy is set to default with spot price")
+func TestRunConfigPrepare_TenancyGood(t *testing.T) {
+	validTenancy := []string{"", "default", "dedicated", "host"}
+	for _, vt := range validTenancy {
+		c := testConfig()
+		c.Tenancy = vt
+		if err := c.Prepare(nil); len(err) != 0 {
+			t.Fatalf("Should not error if tenancy is set to %s", vt)
+		}
 	}
 }