fleet: refactor config

- Explicitly specify all of the valid options for fleet
- Seperate the config from Units()
- Add YAML tags for the fields

system/fleet.go

@@ -0,0 +1,26 @@
+package system
+
+import (
+	"github.com/coreos/coreos-cloudinit/config"
+)
+
+// Fleet is a top-level structure which embeds its underlying configuration,
+// config.Fleet, and provides the system-specific Unit().
+type Fleet struct {
+	config.Fleet
+}
+
+// Units generates a Unit file drop-in for fleet, if any fleet options were
+// configured in cloud-config
+func (fe Fleet) Units(_ string) ([]Unit, error) {
+	content := dropinContents(fe.Fleet)
+	if content == "" {
+		return nil, nil
+	}
+	return []Unit{{
+		Name:    "fleet.service",
+		Runtime: true,
+		DropIn:  true,
+		Content: content,
+	}}, nil
+}

system/fleet_test.go

@@ -0,0 +1,41 @@
+package system
+
+import (
+	"reflect"
+	"testing"
+
+	"github.com/coreos/coreos-cloudinit/config"
+)
+
+func TestFleetUnits(t *testing.T) {
+	for _, tt := range []struct {
+		config config.Fleet
+		units  []Unit
+	}{
+		{
+			config.Fleet{},
+			nil,
+		},
+		{
+			config.Fleet{
+				PublicIP: "12.34.56.78",
+			},
+			[]Unit{{
+				Name: "fleet.service",
+				Content: `[Service]
+Environment="FLEET_PUBLIC_IP=12.34.56.78"
+`,
+				Runtime: true,
+				DropIn:  true,
+			}},
+		},
+	} {
+		units, err := Fleet{tt.config}.Units("")
+		if err != nil {
+			t.Errorf("bad error (%q): want %q, got %q", tt.config, nil, err)
+		}
+		if !reflect.DeepEqual(units, tt.units) {
+			t.Errorf("bad units (%q): want %q, got %q", tt.config, tt.units, units)
+		}
+	}
+}