Factor out API defaulting from validation logic

Currently, the validation logic validates fields in an object and supply default
values wherever applies. This change factors out defaulting to a set of
defaulting callback functions for decoding (see #1502 for more discussion).

 * This change is based on pull request 2587.

 * Most defaulting has been migrated to defaults.go where the defaulting
   functions are added.

 * validation_test.go and converter_test.go have been adapted to not testing the
   default values.

 * Fixed all tests with that create invalid objects with the absence of
   defaulting logic.

pkg/api/testing/fuzzer.go

@@ -32,6 +32,14 @@ import (
 	"speter.net/go/exp/math/dec/inf"
 )
 
+func fuzzOneOf(c fuzz.Continue, objs ...interface{}) {
+	// Use a new fuzzer which cannot populate nil to ensure one obj will be set.
+	// FIXME: would be nicer to use FuzzOnePtr() and reflect.
+	f := fuzz.New().NilChance(0).NumElements(1, 1)
+	i := c.RandUint64() % uint64(len(objs))
+	f.Fuzz(objs[i])
+}
+
 // FuzzerFor can randomly populate api objects that are destined for version.
 func FuzzerFor(t *testing.T, version string, src rand.Source) *fuzz.Fuzzer {
 	f := fuzz.New().NilChance(.5).NumElements(1, 1)
@@ -84,15 +92,18 @@ func FuzzerFor(t *testing.T, version string, src rand.Source) *fuzz.Fuzzer {
 			statuses := []api.PodPhase{api.PodPending, api.PodRunning, api.PodFailed, api.PodUnknown}
 			*j = statuses[c.Rand.Intn(len(statuses))]
 		},
+		func(j *api.PodTemplateSpec, c fuzz.Continue) {
+			// TODO: v1beta1/2 can't round trip a nil template correctly, fix by having v1beta1/2
+			// conversion compare converted object to nil via DeepEqual
+			j.ObjectMeta = api.ObjectMeta{}
+			c.Fuzz(&j.ObjectMeta)
+			j.ObjectMeta = api.ObjectMeta{Labels: j.ObjectMeta.Labels}
+			j.Spec = api.PodSpec{}
+			c.Fuzz(&j.Spec)
+		},
 		func(j *api.ReplicationControllerSpec, c fuzz.Continue) {
-			// TemplateRef must be nil for round trip
+			// TemplateRef is set to nil by omission; this is required for round trip
 			c.Fuzz(&j.Template)
-			if j.Template == nil {
-				// TODO: v1beta1/2 can't round trip a nil template correctly, fix by having v1beta1/2
-				// conversion compare converted object to nil via DeepEqual
-				j.Template = &api.PodTemplateSpec{}
-			}
-			j.Template.ObjectMeta = api.ObjectMeta{Labels: j.Template.ObjectMeta.Labels}
 			c.Fuzz(&j.Selector)
 			j.Replicas = int(c.RandUint64())
 		},
@@ -160,6 +171,46 @@ func FuzzerFor(t *testing.T, version string, src rand.Source) *fuzz.Fuzzer {
 			policies := []api.PullPolicy{api.PullAlways, api.PullNever, api.PullIfNotPresent}
 			*p = policies[c.Rand.Intn(len(policies))]
 		},
+		func(rp *api.RestartPolicy, c fuzz.Continue) {
+			// Exactly one of the fields should be set.
+			fuzzOneOf(c, &rp.Always, &rp.OnFailure, &rp.Never)
+		},
+		func(vs *api.VolumeSource, c fuzz.Continue) {
+			// Exactly one of the fields should be set.
+			//FIXME: the fuzz can still end up nil.  What if fuzz allowed me to say that?
+			fuzzOneOf(c, &vs.HostPath, &vs.EmptyDir, &vs.GCEPersistentDisk, &vs.GitRepo)
+		},
+		func(d *api.DNSPolicy, c fuzz.Continue) {
+			policies := []api.DNSPolicy{api.DNSClusterFirst, api.DNSDefault}
+			*d = policies[c.Rand.Intn(len(policies))]
+		},
+		func(p *api.Protocol, c fuzz.Continue) {
+			protocols := []api.Protocol{api.ProtocolTCP, api.ProtocolUDP}
+			*p = protocols[c.Rand.Intn(len(protocols))]
+		},
+		func(p *api.AffinityType, c fuzz.Continue) {
+			types := []api.AffinityType{api.AffinityTypeClientIP, api.AffinityTypeNone}
+			*p = types[c.Rand.Intn(len(types))]
+		},
+		func(ct *api.Container, c fuzz.Continue) {
+			// This function exists soley to set TerminationMessagePath to a
+			// non-empty string. TODO: consider making TerminationMessagePath a
+			// new type to simplify fuzzing.
+			ct.TerminationMessagePath = api.TerminationMessagePathDefault
+			// Let fuzzer handle the rest of the fileds.
+			c.Fuzz(&ct.Name)
+			c.Fuzz(&ct.Image)
+			c.Fuzz(&ct.Command)
+			c.Fuzz(&ct.Ports)
+			c.Fuzz(&ct.WorkingDir)
+			c.Fuzz(&ct.Env)
+			c.Fuzz(&ct.VolumeMounts)
+			c.Fuzz(&ct.LivenessProbe)
+			c.Fuzz(&ct.Lifecycle)
+			c.Fuzz(&ct.ImagePullPolicy)
+			c.Fuzz(&ct.Privileged)
+			c.Fuzz(&ct.Capabilities)
+		},
 	)
 	return f
 }