Remove unions logic, keep schema components

This removes the generally unused union code from the library in a
non-backward incompatible way since the API was not used anyways. The
schema isn't changed since we don't want to break existing schema (the
unions fields will continue to be just ignored).

internal/fixture/state.go

@@ -535,8 +535,6 @@ type TestCase struct {
 	// Managed, if not nil, is the ManagedFields as expected
 	// after all operations are run.
 	Managed fieldpath.ManagedFields
-	// Set to true if the test case needs the union behavior enabled.
-	RequiresUnions bool
 	// ReportInputOnNoop if we don't want to compare the output and
 	// always return it.
 	ReturnInputOnNoop bool
@@ -576,7 +574,6 @@ func (tc TestCase) BenchWithConverter(parser Parser, converter merge.Converter)
 		Converter:         converter,
 		IgnoredFields:     tc.IgnoredFields,
 		ReturnInputOnNoop: tc.ReturnInputOnNoop,
-		EnableUnions:      tc.RequiresUnions,
 	}
 	state := State{
 		Updater: updaterBuilder.BuildUpdater(),
@@ -599,7 +596,6 @@ func (tc TestCase) TestWithConverter(parser Parser, converter merge.Converter) e
 		Converter:         converter,
 		IgnoredFields:     tc.IgnoredFields,
 		ReturnInputOnNoop: tc.ReturnInputOnNoop,
-		EnableUnions:      tc.RequiresUnions,
 	}
 	state := State{
 		Updater: updaterBuilder.BuildUpdater(),
@@ -636,15 +632,5 @@ func (tc TestCase) TestWithConverter(parser Parser, converter merge.Converter) e
 		}
 	}
 
-	if !tc.RequiresUnions {
-		// Re-run the test with unions on.
-		tc2 := tc
-		tc2.RequiresUnions = true
-		err := tc2.TestWithConverter(parser, converter)
-		if err != nil {
-			return fmt.Errorf("fails if unions are on: %v", err)
-		}
-	}
-
 	return nil
 }

merge/update.go

@@ -34,8 +34,6 @@ type UpdaterBuilder struct {
 	Converter     Converter
 	IgnoredFields map[fieldpath.APIVersion]*fieldpath.Set
 
-	EnableUnions bool
-
 	// Stop comparing the new object with old object after applying.
 	// This was initially used to avoid spurious etcd update, but
 	// since that's vastly inefficient, we've come-up with a better
@@ -49,7 +47,6 @@ func (u *UpdaterBuilder) BuildUpdater() *Updater {
 	return &Updater{
 		Converter:         u.Converter,
 		IgnoredFields:     u.IgnoredFields,
-		enableUnions:      u.EnableUnions,
 		returnInputOnNoop: u.ReturnInputOnNoop,
 	}
 }
@@ -63,19 +60,9 @@ type Updater struct {
 	// Deprecated: This will eventually become private.
 	IgnoredFields map[fieldpath.APIVersion]*fieldpath.Set
 
-	enableUnions bool
-
 	returnInputOnNoop bool
 }
 
-// EnableUnionFeature turns on union handling. It is disabled by default until the
-// feature is complete.
-//
-// Deprecated: Use the builder instead.
-func (s *Updater) EnableUnionFeature() {
-	s.enableUnions = true
-}
-
 func (s *Updater) update(oldObject, newObject *typed.TypedValue, version fieldpath.APIVersion, managers fieldpath.ManagedFields, workflow string, force bool) (fieldpath.ManagedFields, *typed.Comparison, error) {
 	conflicts := fieldpath.ManagedFields{}
 	removed := fieldpath.ManagedFields{}
@@ -160,12 +147,6 @@ func (s *Updater) Update(liveObject, newObject *typed.TypedValue, version fieldp
 	if err != nil {
 		return nil, fieldpath.ManagedFields{}, err
 	}
-	if s.enableUnions {
-		newObject, err = liveObject.NormalizeUnions(newObject)
-		if err != nil {
-			return nil, fieldpath.ManagedFields{}, err
-		}
-	}
 	managers, compare, err := s.update(liveObject, newObject, version, managers, manager, true)
 	if err != nil {
 		return nil, fieldpath.ManagedFields{}, err
@@ -198,22 +179,10 @@ func (s *Updater) Apply(liveObject, configObject *typed.TypedValue, version fiel
 	if err != nil {
 		return nil, fieldpath.ManagedFields{}, err
 	}
-	if s.enableUnions {
-		configObject, err = configObject.NormalizeUnionsApply(configObject)
-		if err != nil {
-			return nil, fieldpath.ManagedFields{}, err
-		}
-	}
 	newObject, err := liveObject.Merge(configObject)
 	if err != nil {
 		return nil, fieldpath.ManagedFields{}, fmt.Errorf("failed to merge config: %v", err)
 	}
-	if s.enableUnions {
-		newObject, err = configObject.NormalizeUnionsApply(newObject)
-		if err != nil {
-			return nil, fieldpath.ManagedFields{}, err
-		}
-	}
 	lastSet := managers[manager]
 	set, err := configObject.ToFieldSet()
 	if err != nil {