Simplify code base.

- In ResMap, drop concept of internal Id to Resource
   map.  The ResMap is now (just) a list, allowing only
   very particular edits.

 - Resources should now be maintained in the order
   loaded.  A later PR can adjust tests to remove the
   internal legacy sorting, and confirm order-out is
   predictable from order-in.  The PR would suppress
   the sort in tests, and reorder the output to make
   all tests pass again, and confirm that the new order
   matched depth-first input traversal.  The FromMap
   fixture function was removed from all test inputs to
   establish a predictable input order.

 - Resources now have two 'Ids', OriginalId and
   CurrentId.  The former is fixed as
   GVK-name-namespace at load time, the latter changes
   during transformations.  The latter can be used to
   narrow name references when the former maps to
   multiple resources.  We allow bases to be loaded
   more than once in a build (a diamond pattern), so
   the OriginalId is not unique across the resources
   set.  The CurrentId is (and must be) unique, but is
   constantly mutating.  Failing to make this
   distinction clear, and attempting to maintain a
   mapping from a single mutating Id to a resource was
   making the code too complex.

 - Drop prefix/suffix from ResId - the ResId is now
   immutable.  A later PR can remove the distinction
   with ItemId.

 - This PR increases coverage of ResMap is since this
   is a large refactor.  Higher level tests didn't need
   much change outside reordering of results at the
   resource level.

plugin/builtin/AnnotationsTransformer.go

@@ -15,6 +15,7 @@ type AnnotationsTransformerPlugin struct {
 	FieldSpecs  []config.FieldSpec `json:"fieldSpecs,omitempty" yaml:"fieldSpecs,omitempty"`
 }
 
+//noinspection GoUnusedGlobalVariable
 func NewAnnotationsTransformerPlugin() *AnnotationsTransformerPlugin {
 	return &AnnotationsTransformerPlugin{}
 }

plugin/builtin/ConfigMapGenerator.go

@@ -15,6 +15,7 @@ type ConfigMapGeneratorPlugin struct {
 	types.ConfigMapArgs
 }
 
+//noinspection GoUnusedGlobalVariable
 func NewConfigMapGeneratorPlugin() *ConfigMapGeneratorPlugin {
 	return &ConfigMapGeneratorPlugin{}
 }

plugin/builtin/HashTransformer.go

@@ -12,6 +12,7 @@ type HashTransformerPlugin struct {
 	hasher ifc.KunstructuredHasher
 }
 
+//noinspection GoUnusedGlobalVariable
 func NewHashTransformerPlugin() *HashTransformerPlugin {
 	return &HashTransformerPlugin{}
 }

plugin/builtin/ImageTagTransformer.go

@@ -17,6 +17,7 @@ type ImageTagTransformerPlugin struct {
 	FieldSpecs []config.FieldSpec `json:"fieldSpecs,omitempty" yaml:"fieldSpecs,omitempty"`
 }
 
+//noinspection GoUnusedGlobalVariable
 func NewImageTagTransformerPlugin() *ImageTagTransformerPlugin {
 	return &ImageTagTransformerPlugin{}
 }

plugin/builtin/InventoryTransformer.go

@@ -3,7 +3,6 @@ package builtin
 
 import (
 	"fmt"
-	"strings"
 
 	"sigs.k8s.io/kustomize/pkg/resource"
 
@@ -24,6 +23,7 @@ type InventoryTransformerPlugin struct {
 	Namespace string `json:"namespace,omitempty" yaml:"namespace,omitempty"`
 }
 
+//noinspection GoUnusedGlobalVariable
 func NewInventoryTransformerPlugin() *InventoryTransformerPlugin {
 	return &InventoryTransformerPlugin{}
 }
@@ -98,32 +98,33 @@ func makeInventory(m resmap.ResMap) (
 	inv = inventory.NewInventory()
 	var keys []string
 	for _, r := range m.Resources() {
-		ns := getNamespace(r)
-		item := resid.NewItemId(r.GetGvk(), ns, r.GetName())
+		ns := r.GetNamespace()
+		item := resid.NewResIdWithNamespace(r.GetGvk(), r.GetName(), ns)
 		if _, ok := inv.Current[item]; ok {
 			return nil, "", fmt.Errorf(
 				"item '%v' already in inventory", item)
 		}
-		inv.Current[item] = computeRefs(r, m)
+		inv.Current[item], err = computeRefs(r, m)
+		if err != nil {
+			return nil, "", err
+		}
 		keys = append(keys, item.String())
 	}
 	h, err := hasher.SortArrayAndComputeHash(keys)
 	return inv, h, err
 }
 
-func getNamespace(r *resource.Resource) string {
-	ns, err := r.GetFieldValue("metadata.namespace")
-	if err != nil && !strings.Contains(err.Error(), "no field named") {
-		panic(err)
-	}
-	return ns
-}
-
-func computeRefs(r *resource.Resource, m resmap.ResMap) (refs []resid.ItemId) {
+func computeRefs(
+	r *resource.Resource, m resmap.ResMap) (refs []resid.ResId, err error) {
 	for _, refid := range r.GetRefBy() {
-		ref := m.GetById(refid)
-		ns := getNamespace(ref)
-		refs = append(refs, resid.NewItemId(ref.GetGvk(), ns, ref.GetName()))
+		ref, err := m.GetByCurrentId(refid)
+		if err != nil {
+			return nil, err
+		}
+		refs = append(
+			refs,
+			resid.NewResIdWithNamespace(
+				ref.GetGvk(), ref.GetName(), ref.GetNamespace()))
 	}
 	return
 }

plugin/builtin/LabelTransformer.go

@@ -15,6 +15,7 @@ type LabelTransformerPlugin struct {
 	FieldSpecs []config.FieldSpec `json:"fieldSpecs,omitempty" yaml:"fieldSpecs,omitempty"`
 }
 
+//noinspection GoUnusedGlobalVariable
 func NewLabelTransformerPlugin() *LabelTransformerPlugin {
 	return &LabelTransformerPlugin{}
 }

plugin/builtin/LegacyOrderTransformer.go

@@ -2,6 +2,7 @@
 package builtin
 
 import (
+	"github.com/pkg/errors"
 	"sigs.k8s.io/kustomize/pkg/ifc"
 	"sigs.k8s.io/kustomize/pkg/resmap"
 	"sigs.k8s.io/kustomize/pkg/resource"
@@ -15,6 +16,7 @@ import (
 // (like ValidatingWebhookConfiguration) last.
 type LegacyOrderTransformerPlugin struct{}
 
+//noinspection GoUnusedGlobalVariable
 func NewLegacyOrderTransformerPlugin() *LegacyOrderTransformerPlugin {
 	return &LegacyOrderTransformerPlugin{}
 }
@@ -25,16 +27,19 @@ func (p *LegacyOrderTransformerPlugin) Config(
 	return nil
 }
 
-func (p *LegacyOrderTransformerPlugin) Transform(m resmap.ResMap) error {
+func (p *LegacyOrderTransformerPlugin) Transform(m resmap.ResMap) (err error) {
 	resources := make([]*resource.Resource, m.Size())
 	ids := m.AllIds()
 	sort.Sort(resmap.IdSlice(ids))
 	for i, id := range ids {
-		resources[i] = m.GetById(id)
+		resources[i], err = m.GetByCurrentId(id)
+		if err != nil {
+			return errors.Wrap(err, "expected match for sorting")
+		}
 	}
 	m.Clear()
-	for i, id := range ids {
-		m.AppendWithId(id, resources[i])
+	for _, r := range resources {
+		m.Append(r)
 	}
 	return nil
 }

plugin/builtin/NamespaceTransformer.go

@@ -15,6 +15,7 @@ type NamespaceTransformerPlugin struct {
 	FieldSpecs []config.FieldSpec `json:"fieldSpecs,omitempty" yaml:"fieldSpecs,omitempty"`
 }
 
+//noinspection GoUnusedGlobalVariable
 func NewNamespaceTransformerPlugin() *NamespaceTransformerPlugin {
 	return &NamespaceTransformerPlugin{}
 }

plugin/builtin/PatchJson6902Transformer.go

@@ -14,6 +14,7 @@ type PatchJson6902TransformerPlugin struct {
 	Patches []types.PatchJson6902 `json:"patches,omitempty" yaml:"patches,omitempty"`
 }
 
+//noinspection GoUnusedGlobalVariable
 func NewPatchJson6902TransformerPlugin() *PatchJson6902TransformerPlugin {
 	return &PatchJson6902TransformerPlugin{}
 }

plugin/builtin/PrefixSuffixTransformer.go

@@ -7,6 +7,7 @@ import (
 
 	"sigs.k8s.io/kustomize/pkg/gvk"
 	"sigs.k8s.io/kustomize/pkg/ifc"
+	"sigs.k8s.io/kustomize/pkg/resid"
 	"sigs.k8s.io/kustomize/pkg/resmap"
 	"sigs.k8s.io/kustomize/pkg/transformers"
 	"sigs.k8s.io/kustomize/pkg/transformers/config"
@@ -20,6 +21,7 @@ type PrefixSuffixTransformerPlugin struct {
 	FieldSpecs []config.FieldSpec `json:"fieldSpecs,omitempty" yaml:"fieldSpecs,omitempty"`
 }
 
+//noinspection GoUnusedGlobalVariable
 func NewPrefixSuffixTransformerPlugin() *PrefixSuffixTransformerPlugin {
 	return &PrefixSuffixTransformerPlugin{}
 }
@@ -50,46 +52,54 @@ func (p *PrefixSuffixTransformerPlugin) Transform(m resmap.ResMap) error {
 	if len(p.Prefix) == 0 && len(p.Suffix) == 0 {
 		return nil
 	}
-
-	// Fill map "mf" with entries subject to name modification, and
-	// delete these entries from "m", so that for now m retains only
-	// the entries whose names will not be modified.
-	mf := resmap.New()
-	for id, r := range m.AsMap() {
-		found := false
-		for _, path := range prefixSuffixFieldSpecsToSkip {
-			if id.Gvk().IsSelected(&path.Gvk) {
-				found = true
-				break
-			}
+	for _, r := range m.Resources() {
+		if p.shouldSkip(r.OrgId()) {
+			continue
 		}
-		if !found {
-			mf.AppendWithId(id, r)
-			m.Remove(id)
+		fs, ok := p.shouldInclude(r.OrgId())
+		if !ok {
+			continue
 		}
-	}
-
-	for id, r := range mf.AsMap() {
-		objMap := r.Map()
-		for _, path := range p.FieldSpecs {
-			if !id.Gvk().IsSelected(&path.Gvk) {
-				continue
-			}
-			err := transformers.MutateField(
-				objMap,
-				path.PathSlice(),
-				path.CreateIfNotPresent,
-				p.addPrefixSuffix)
-			if err != nil {
-				return err
-			}
-			newId := id.CopyWithNewPrefixSuffix(p.Prefix, p.Suffix)
-			m.AppendWithId(newId, r)
+		if smellsLikeANameChange(fs) {
+			r.AddNamePrefix(p.Prefix)
+			r.AddNameSuffix(p.Suffix)
+		}
+		err := transformers.MutateField(
+			r.Map(),
+			fs.PathSlice(),
+			fs.CreateIfNotPresent,
+			p.addPrefixSuffix)
+		if err != nil {
+			return err
 		}
 	}
 	return nil
 }
 
+func smellsLikeANameChange(fs *config.FieldSpec) bool {
+	return fs.Path == "metadata/name"
+}
+
+func (p *PrefixSuffixTransformerPlugin) shouldInclude(
+	id resid.ResId) (*config.FieldSpec, bool) {
+	for _, path := range p.FieldSpecs {
+		if id.IsSelected(&path.Gvk) {
+			return &path, true
+		}
+	}
+	return nil, false
+}
+
+func (p *PrefixSuffixTransformerPlugin) shouldSkip(
+	id resid.ResId) bool {
+	for _, path := range prefixSuffixFieldSpecsToSkip {
+		if id.IsSelected(&path.Gvk) {
+			return true
+		}
+	}
+	return false
+}
+
 func (p *PrefixSuffixTransformerPlugin) addPrefixSuffix(
 	in interface{}) (interface{}, error) {
 	s, ok := in.(string)

plugin/builtin/ReplicaCountTransformer.go

@@ -22,6 +22,7 @@ type ReplicaCountTransformerPlugin struct {
 	Replica types.Replica `json:"replica,omitempty" yaml:"replica,omitempty"`
 }
 
+//noinspection GoUnusedGlobalVariable
 func NewReplicaCountTransformerPlugin() *ReplicaCountTransformerPlugin {
 	return &ReplicaCountTransformerPlugin{}
 }
@@ -35,11 +36,11 @@ func (p *ReplicaCountTransformerPlugin) Config(
 
 func (p *ReplicaCountTransformerPlugin) Transform(m resmap.ResMap) error {
 	matcher := func(r resid.ResId) bool {
-		return r.ItemId.Name == p.Replica.Name
+		return r.Name == p.Replica.Name
 	}
 
-	for _, id := range m.GetMatchingIds(matcher) {
-		kMap := m.GetById(id).Map()
+	for _, r := range m.GetMatchingResourcesByOriginalId(matcher) {
+		kMap := r.Map()
 
 		specInterface, ok := kMap[fldSpec]
 		if !ok {

plugin/builtin/SecretGenerator.go

@@ -15,6 +15,7 @@ type SecretGeneratorPlugin struct {
 	types.SecretArgs
 }
 
+//noinspection GoUnusedGlobalVariable
 func NewSecretGeneratorPlugin() *SecretGeneratorPlugin {
 	return &SecretGeneratorPlugin{}
 }

plugin/builtin/annotationstransformer/AnnotationsTransformer.go

@@ -18,6 +18,7 @@ type plugin struct {
 	FieldSpecs  []config.FieldSpec `json:"fieldSpecs,omitempty" yaml:"fieldSpecs,omitempty"`
 }
 
+//noinspection GoUnusedGlobalVariable
 var KustomizePlugin plugin
 
 func (p *plugin) Config(

plugin/builtin/configmapgenerator/ConfigMapGenerator.go

@@ -18,6 +18,7 @@ type plugin struct {
 	types.ConfigMapArgs
 }
 
+//noinspection GoUnusedGlobalVariable
 var KustomizePlugin plugin
 
 func (p *plugin) Config(

plugin/builtin/hashtransformer/HashTransformer.go

@@ -15,6 +15,7 @@ type plugin struct {
 	hasher ifc.KunstructuredHasher
 }
 
+//noinspection GoUnusedGlobalVariable
 var KustomizePlugin plugin
 
 func (p *plugin) Config(

plugin/builtin/imagetagtransformer/ImageTagTransformer.go

@@ -20,6 +20,7 @@ type plugin struct {
 	FieldSpecs []config.FieldSpec `json:"fieldSpecs,omitempty" yaml:"fieldSpecs,omitempty"`
 }
 
+//noinspection GoUnusedGlobalVariable
 var KustomizePlugin plugin
 
 func (p *plugin) Config(

plugin/builtin/inventorytransformer/InventoryTransformer.go

@@ -6,7 +6,6 @@ package main
 
 import (
 	"fmt"
-	"strings"
 
 	"sigs.k8s.io/kustomize/pkg/resource"
 
@@ -27,6 +26,7 @@ type plugin struct {
 	Namespace string `json:"namespace,omitempty" yaml:"namespace,omitempty"`
 }
 
+//noinspection GoUnusedGlobalVariable
 var KustomizePlugin plugin
 
 func (p *plugin) Config(
@@ -99,32 +99,33 @@ func makeInventory(m resmap.ResMap) (
 	inv = inventory.NewInventory()
 	var keys []string
 	for _, r := range m.Resources() {
-		ns := getNamespace(r)
-		item := resid.NewItemId(r.GetGvk(), ns, r.GetName())
+		ns := r.GetNamespace()
+		item := resid.NewResIdWithNamespace(r.GetGvk(), r.GetName(), ns)
 		if _, ok := inv.Current[item]; ok {
 			return nil, "", fmt.Errorf(
 				"item '%v' already in inventory", item)
 		}
-		inv.Current[item] = computeRefs(r, m)
+		inv.Current[item], err = computeRefs(r, m)
+		if err != nil {
+			return nil, "", err
+		}
 		keys = append(keys, item.String())
 	}
 	h, err := hasher.SortArrayAndComputeHash(keys)
 	return inv, h, err
 }
 
-func getNamespace(r *resource.Resource) string {
-	ns, err := r.GetFieldValue("metadata.namespace")
-	if err != nil && !strings.Contains(err.Error(), "no field named") {
-		panic(err)
-	}
-	return ns
-}
-
-func computeRefs(r *resource.Resource, m resmap.ResMap) (refs []resid.ItemId) {
+func computeRefs(
+	r *resource.Resource, m resmap.ResMap) (refs []resid.ResId, err error) {
 	for _, refid := range r.GetRefBy() {
-		ref := m.GetById(refid)
-		ns := getNamespace(ref)
-		refs = append(refs, resid.NewItemId(ref.GetGvk(), ns, ref.GetName()))
+		ref, err := m.GetByCurrentId(refid)
+		if err != nil {
+			return nil, err
+		}
+		refs = append(
+			refs,
+			resid.NewResIdWithNamespace(
+				ref.GetGvk(), ref.GetName(), ref.GetNamespace()))
 	}
 	return
 }

plugin/builtin/labeltransformer/LabelTransformer.go

@@ -18,6 +18,7 @@ type plugin struct {
 	FieldSpecs []config.FieldSpec `json:"fieldSpecs,omitempty" yaml:"fieldSpecs,omitempty"`
 }
 
+//noinspection GoUnusedGlobalVariable
 var KustomizePlugin plugin
 
 func (p *plugin) Config(

plugin/builtin/legacyordertransformer/LegacyOrderTransformer.go

@@ -5,6 +5,7 @@
 package main
 
 import (
+	"github.com/pkg/errors"
 	"sigs.k8s.io/kustomize/pkg/ifc"
 	"sigs.k8s.io/kustomize/pkg/resmap"
 	"sigs.k8s.io/kustomize/pkg/resource"
@@ -18,6 +19,7 @@ import (
 // (like ValidatingWebhookConfiguration) last.
 type plugin struct{}
 
+//noinspection GoUnusedGlobalVariable
 var KustomizePlugin plugin
 
 // Nothing needed for configuration.
@@ -26,16 +28,19 @@ func (p *plugin) Config(
 	return nil
 }
 
-func (p *plugin) Transform(m resmap.ResMap) error {
+func (p *plugin) Transform(m resmap.ResMap) (err error) {
 	resources := make([]*resource.Resource, m.Size())
 	ids := m.AllIds()
 	sort.Sort(resmap.IdSlice(ids))
 	for i, id := range ids {
-		resources[i] = m.GetById(id)
+		resources[i], err = m.GetByCurrentId(id)
+		if err != nil {
+			return errors.Wrap(err, "expected match for sorting")
+		}
 	}
 	m.Clear()
-	for i, id := range ids {
-		m.AppendWithId(id, resources[i])
+	for _, r := range resources {
+		m.Append(r)
 	}
 	return nil
 }

plugin/builtin/namespacetransformer/NamespaceTransformer.go

@@ -18,6 +18,7 @@ type plugin struct {
 	FieldSpecs []config.FieldSpec `json:"fieldSpecs,omitempty" yaml:"fieldSpecs,omitempty"`
 }
 
+//noinspection GoUnusedGlobalVariable
 var KustomizePlugin plugin
 
 func (p *plugin) Config(

plugin/builtin/patchjson6902transformer/PatchJson6902Transformer.go

@@ -17,6 +17,7 @@ type plugin struct {
 	Patches []types.PatchJson6902 `json:"patches,omitempty" yaml:"patches,omitempty"`
 }
 
+//noinspection GoUnusedGlobalVariable
 var KustomizePlugin plugin
 
 func (p *plugin) Config(

plugin/builtin/prefixsuffixtransformer/PrefixSuffixTransformer.go

@@ -10,6 +10,7 @@ import (
 
 	"sigs.k8s.io/kustomize/pkg/gvk"
 	"sigs.k8s.io/kustomize/pkg/ifc"
+	"sigs.k8s.io/kustomize/pkg/resid"
 	"sigs.k8s.io/kustomize/pkg/resmap"
 	"sigs.k8s.io/kustomize/pkg/transformers"
 	"sigs.k8s.io/kustomize/pkg/transformers/config"
@@ -23,6 +24,7 @@ type plugin struct {
 	FieldSpecs []config.FieldSpec `json:"fieldSpecs,omitempty" yaml:"fieldSpecs,omitempty"`
 }
 
+//noinspection GoUnusedGlobalVariable
 var KustomizePlugin plugin
 
 // Not placed in a file yet due to lack of demand.
@@ -51,46 +53,54 @@ func (p *plugin) Transform(m resmap.ResMap) error {
 	if len(p.Prefix) == 0 && len(p.Suffix) == 0 {
 		return nil
 	}
-
-	// Fill map "mf" with entries subject to name modification, and
-	// delete these entries from "m", so that for now m retains only
-	// the entries whose names will not be modified.
-	mf := resmap.New()
-	for id, r := range m.AsMap() {
-		found := false
-		for _, path := range prefixSuffixFieldSpecsToSkip {
-			if id.Gvk().IsSelected(&path.Gvk) {
-				found = true
-				break
-			}
+	for _, r := range m.Resources() {
+		if p.shouldSkip(r.OrgId()) {
+			continue
 		}
-		if !found {
-			mf.AppendWithId(id, r)
-			m.Remove(id)
+		fs, ok := p.shouldInclude(r.OrgId())
+		if !ok {
+			continue
 		}
-	}
-
-	for id, r := range mf.AsMap() {
-		objMap := r.Map()
-		for _, path := range p.FieldSpecs {
-			if !id.Gvk().IsSelected(&path.Gvk) {
-				continue
-			}
-			err := transformers.MutateField(
-				objMap,
-				path.PathSlice(),
-				path.CreateIfNotPresent,
-				p.addPrefixSuffix)
-			if err != nil {
-				return err
-			}
-			newId := id.CopyWithNewPrefixSuffix(p.Prefix, p.Suffix)
-			m.AppendWithId(newId, r)
+		if smellsLikeANameChange(fs) {
+			r.AddNamePrefix(p.Prefix)
+			r.AddNameSuffix(p.Suffix)
+		}
+		err := transformers.MutateField(
+			r.Map(),
+			fs.PathSlice(),
+			fs.CreateIfNotPresent,
+			p.addPrefixSuffix)
+		if err != nil {
+			return err
 		}
 	}
 	return nil
 }
 
+func smellsLikeANameChange(fs *config.FieldSpec) bool {
+	return fs.Path == "metadata/name"
+}
+
+func (p *plugin) shouldInclude(
+	id resid.ResId) (*config.FieldSpec, bool) {
+	for _, path := range p.FieldSpecs {
+		if id.IsSelected(&path.Gvk) {
+			return &path, true
+		}
+	}
+	return nil, false
+}
+
+func (p *plugin) shouldSkip(
+	id resid.ResId) bool {
+	for _, path := range prefixSuffixFieldSpecsToSkip {
+		if id.IsSelected(&path.Gvk) {
+			return true
+		}
+	}
+	return false
+}
+
 func (p *plugin) addPrefixSuffix(
 	in interface{}) (interface{}, error) {
 	s, ok := in.(string)

plugin/builtin/replicacounttransformer/ReplicaCountTransformer.go

@@ -25,6 +25,7 @@ type plugin struct {
 	Replica types.Replica `json:"replica,omitempty" yaml:"replica,omitempty"`
 }
 
+//noinspection GoUnusedGlobalVariable
 var KustomizePlugin plugin
 
 func (p *plugin) Config(
@@ -36,11 +37,11 @@ func (p *plugin) Config(
 
 func (p *plugin) Transform(m resmap.ResMap) error {
 	matcher := func(r resid.ResId) bool {
-		return r.ItemId.Name == p.Replica.Name
+		return r.Name == p.Replica.Name
 	}
 
-	for _, id := range m.GetMatchingIds(matcher) {
-		kMap := m.GetById(id).Map()
+	for _, r := range m.GetMatchingResourcesByOriginalId(matcher) {
+		kMap := r.Map()
 
 		specInterface, ok := kMap[fldSpec]
 		if !ok {

plugin/builtin/secretgenerator/SecretGenerator.go

@@ -18,6 +18,7 @@ type plugin struct {
 	types.SecretArgs
 }
 
+//noinspection GoUnusedGlobalVariable
 var KustomizePlugin plugin
 
 func (p *plugin) Config(