Report unused variables.

pkg/transformers/refvars.go

@@ -2,28 +2,26 @@ package transformers
 
 import (
 	"fmt"
-
 	"sigs.k8s.io/kustomize/pkg/expansion"
 	"sigs.k8s.io/kustomize/pkg/resmap"
 	"sigs.k8s.io/kustomize/pkg/transformers/config"
 )
 
-type refvarTransformer struct {
-	fieldSpecs  []config.FieldSpec
-	mappingFunc func(string) string
+type RefVarTransformer struct {
+	varMap            map[string]string
+	replacementCounts map[string]int
+	fieldSpecs        []config.FieldSpec
+	mappingFunc       func(string) string
 }
 
-// NewRefVarTransformer returns a Transformer that replaces $(VAR) style
-// variables with values.
+// NewRefVarTransformer returns a new RefVarTransformer
+// that replaces $(VAR) style variables with values.
 // The fieldSpecs are the places to look for occurrences of $(VAR).
 func NewRefVarTransformer(
-	varMap map[string]string, fs []config.FieldSpec) Transformer {
-	if len(varMap) == 0 {
-		return NewNoOpTransformer()
-	}
-	return &refvarTransformer{
-		fieldSpecs:  fs,
-		mappingFunc: expansion.MappingFuncFor(varMap),
+	varMap map[string]string, fs []config.FieldSpec) *RefVarTransformer {
+	return &RefVarTransformer{
+		varMap:     varMap,
+		fieldSpecs: fs,
 	}
 }
 
@@ -31,7 +29,7 @@ func NewRefVarTransformer(
 // embedded instances of $VAR style variables, e.g. a container command string.
 // The function returns the string with the variables expanded to their final
 // values.
-func (rv *refvarTransformer) replaceVars(in interface{}) (interface{}, error) {
+func (rv *RefVarTransformer) replaceVars(in interface{}) (interface{}, error) {
 	switch vt := in.(type) {
 	case []interface{}:
 		var xs []string
@@ -63,8 +61,24 @@ func (rv *refvarTransformer) replaceVars(in interface{}) (interface{}, error) {
 	}
 }
 
+// UnusedVars returns slice of Var names that were unused
+// after a Transform run.
+func (rv *RefVarTransformer) UnusedVars() []string {
+	var unused []string
+	for k := range rv.varMap {
+		_, ok := rv.replacementCounts[k]
+		if !ok {
+			unused = append(unused, k)
+		}
+	}
+	return unused
+}
+
 // Transform replaces $(VAR) style variables with values.
-func (rv *refvarTransformer) Transform(m resmap.ResMap) error {
+func (rv *RefVarTransformer) Transform(m resmap.ResMap) error {
+	rv.replacementCounts = make(map[string]int)
+	rv.mappingFunc = expansion.MappingFuncFor(
+		rv.replacementCounts, rv.varMap)
 	for id, res := range m {
 		for _, fieldSpec := range rv.fieldSpecs {
 			if id.Gvk().IsSelected(&fieldSpec.Gvk) {

pkg/transformers/refvars_test.go

@@ -5,7 +5,6 @@ import (
 	"testing"
 
 	"sigs.k8s.io/kustomize/pkg/resid"
-
 	"sigs.k8s.io/kustomize/pkg/resmap"
 	"sigs.k8s.io/kustomize/pkg/transformers/config"
 )
@@ -17,7 +16,8 @@ func TestVarRef(t *testing.T) {
 		res    resmap.ResMap
 	}
 	type expected struct {
-		res resmap.ResMap
+		res    resmap.ResMap
+		unused []string
 	}
 	testCases := []struct {
 		description string
@@ -28,7 +28,8 @@ func TestVarRef(t *testing.T) {
 			description: "var replacement in map[string]",
 			given: given{
 				varMap: map[string]string{
-					"FOO": "BAR",
+					"FOO": "replacementForFoo",
+					"BAR": "replacementForBar",
 				},
 				fs: []config.FieldSpec{
 					{Gvk: cmap, Path: "data"},
@@ -58,11 +59,12 @@ func TestVarRef(t *testing.T) {
 								"name": "cm1",
 							},
 							"data": map[string]interface{}{
-								"item1": "BAR",
+								"item1": "replacementForFoo",
 								"item2": "bla",
 							},
 						}),
 				},
+				unused: []string{"BAR"},
 			},
 		},
 	}