init: simplify CloudConfigUnit interface

initialize/config.go

@@ -22,7 +22,7 @@ type CloudConfigFile interface {
 // CloudConfigUnit represents a CoreOS specific configuration option that can generate
 // associated system.Units to be created/enabled appropriately
 type CloudConfigUnit interface {
-	Units() ([]system.Unit, error)
+	Units() []system.Unit
 }
 
 // Apply renders a CloudConfig to an Environment. This can involve things like
@@ -117,11 +117,7 @@ func Apply(cfg config.CloudConfig, env *Environment) error {
 		system.Fleet{cfg.Coreos.Fleet},
 		system.Update{cfg.Coreos.Update, system.DefaultReadConfig},
 	} {
-		u, err := ccu.Units()
-		if err != nil {
-			return err
-		}
-		units = append(units, u...)
+		units = append(units, ccu.Units()...)
 	}
 
 	wroteEnvironment := false

system/etcd.go

@@ -11,15 +11,15 @@ type Etcd struct {
 }
 
 // Units creates a Unit file drop-in for etcd, using any configured options.
-func (ee Etcd) Units() ([]Unit, error) {
+func (ee Etcd) Units() []Unit {
 	content := dropinContents(ee.Etcd)
 	if content == "" {
-		return nil, nil
+		return nil
 	}
 	return []Unit{{config.Unit{
 		Name:    "etcd.service",
 		Runtime: true,
 		DropIn:  true,
 		Content: content,
-	}}}, nil
+	}}}
 }

system/etcd_test.go

@@ -49,10 +49,7 @@ Environment="ETCD_PEER_BIND_ADDR=127.0.0.1:7002"
 			}}},
 		},
 	} {
-		units, err := Etcd{tt.config}.Units()
-		if err != nil {
-			t.Errorf("bad error (%q): want %q, got %q", tt.config, nil, err)
-		}
+		units := Etcd{tt.config}.Units()
 		if !reflect.DeepEqual(tt.units, units) {
 			t.Errorf("bad units (%q): want %#v, got %#v", tt.config, tt.units, units)
 		}

system/fleet.go

@@ -12,15 +12,15 @@ type Fleet struct {
 
 // Units generates a Unit file drop-in for fleet, if any fleet options were
 // configured in cloud-config
-func (fe Fleet) Units() ([]Unit, error) {
+func (fe Fleet) Units() []Unit {
 	content := dropinContents(fe.Fleet)
 	if content == "" {
-		return nil, nil
+		return nil
 	}
 	return []Unit{{config.Unit{
 		Name:    "fleet.service",
 		Runtime: true,
 		DropIn:  true,
 		Content: content,
-	}}}, nil
+	}}}
 }

system/fleet_test.go

@@ -30,10 +30,7 @@ Environment="FLEET_PUBLIC_IP=12.34.56.78"
 			}}},
 		},
 	} {
-		units, err := Fleet{tt.config}.Units()
-		if err != nil {
-			t.Errorf("bad error (%q): want %q, got %q", tt.config, nil, err)
-		}
+		units := Fleet{tt.config}.Units()
 		if !reflect.DeepEqual(units, tt.units) {
 			t.Errorf("bad units (%q): want %q, got %q", tt.config, tt.units, units)
 		}

system/update.go

@@ -100,7 +100,7 @@ func (uc Update) File() (*File, error) {
 // Units generates units for the cloud-init initializer to act on:
 // - a locksmith Unit, if "reboot-strategy" was set in cloud-config
 // - an update_engine Unit, if "group" or "server" was set in cloud-config
-func (uc Update) Units() ([]Unit, error) {
+func (uc Update) Units() []Unit {
 	var units []Unit
 	if uc.Config.RebootStrategy != "" {
 		ls := &Unit{config.Unit{
@@ -125,7 +125,7 @@ func (uc Update) Units() ([]Unit, error) {
 		units = append(units, ue)
 	}
 
-	return units, nil
+	return units
 }
 
 func sortedKeys(m map[string]string) (keys []string) {

system/update_test.go

@@ -66,10 +66,7 @@ func TestUpdateUnits(t *testing.T) {
 			}}},
 		},
 	} {
-		units, err := Update{tt.config, testReadConfig("")}.Units()
-		if !reflect.DeepEqual(tt.err, err) {
-			t.Errorf("bad error (%q): want %q, got %q", tt.config, tt.err, err)
-		}
+		units := Update{tt.config, testReadConfig("")}.Units()
 		if !reflect.DeepEqual(tt.units, units) {
 			t.Errorf("bad units (%q): want %#v, got %#v", tt.config, tt.units, units)
 		}