Add ability to specify behavior when running "kustomize edit add configmap" command

kustomize/internal/commands/edit/add/configmap.go

@@ -18,7 +18,7 @@ func newCmdAddConfigMap(
 	kf ifc.KunstructuredFactory) *cobra.Command {
 	var flags flagsAndArgs
 	cmd := &cobra.Command{
-		Use:   "configmap NAME [--from-file=[key=]source] [--from-literal=key1=value1]",
+		Use:   "configmap NAME [--behavior={create|merge|replace}] [--from-file=[key=]source] [--from-literal=key1=value1]",
 		Short: "Adds a configmap to the kustomization file.",
 		Long:  "",
 		Example: `
@@ -30,6 +30,9 @@ func newCmdAddConfigMap(
 
 	# Adds a configmap from env-file
 	kustomize edit add configmap my-configmap --from-env-file=env/path.env
+
+	# Adds a configmap from env-file with behavior merge
+	kustomize edit add configmap my-configmap --behavior=merge --from-env-file=env/path.env	
 `,
 		RunE: func(_ *cobra.Command, args []string) error {
 			err := flags.ExpandFileSource(fSys)
@@ -86,6 +89,13 @@ func newCmdAddConfigMap(
 		"disableNameSuffixHash",
 		false,
 		"Disable the name suffix for the configmap")
+	cmd.Flags().StringVar(
+		&flags.Behavior,
+		"behavior",
+		"",
+		"Specify the behavior for config map generation, i.e whether to create a new configmap (the default),  "+
+			"to merge with a previously defined one, or to replace an existing one. Merge and replace should be used only "+
+			" when overriding an existing configmap defined in a base")
 
 	return cmd
 }
@@ -136,4 +146,7 @@ func mergeFlagsIntoCmArgs(args *types.ConfigMapArgs, flags flagsAndArgs) {
 			DisableNameSuffixHash: true,
 		}
 	}
+	if flags.Behavior != "" {
+		args.Behavior = flags.Behavior
+	}
 }

kustomize/internal/commands/edit/add/configmap_test.go

@@ -110,3 +110,41 @@ func TestMergeFlagsIntoConfigMapArgs_EnvSource(t *testing.T) {
 		t.Fatalf("expected env2")
 	}
 }
+
+func TestMergeFlagsIntoConfigMapArgs_Behavior(t *testing.T) {
+	k := &types.Kustomization{}
+	args := findOrMakeConfigMapArgs(k, "foo")
+
+	createBehaviorFlags := flagsAndArgs{
+		Behavior:      "create",
+		EnvFileSource: "env1",
+	}
+	mergeFlagsIntoGeneratorArgs(
+		&args.GeneratorArgs,
+		createBehaviorFlags)
+	if k.ConfigMapGenerator[0].Behavior != "create" {
+		t.Fatalf("expected create")
+	}
+
+	mergeBehaviorFlags := flagsAndArgs{
+		Behavior:      "merge",
+		EnvFileSource: "env1",
+	}
+	mergeFlagsIntoGeneratorArgs(
+		&args.GeneratorArgs,
+		mergeBehaviorFlags)
+	if k.ConfigMapGenerator[0].Behavior != "merge" {
+		t.Fatalf("expected merge")
+	}
+
+	replaceBehaviorFlags := flagsAndArgs{
+		Behavior:      "replace",
+		EnvFileSource: "env1",
+	}
+	mergeFlagsIntoGeneratorArgs(
+		&args.GeneratorArgs,
+		replaceBehaviorFlags)
+	if k.ConfigMapGenerator[0].Behavior != "replace" {
+		t.Fatalf("expected replace")
+	}
+}

kustomize/internal/commands/edit/add/flagsandargs.go

@@ -7,6 +7,8 @@ import (
 	"fmt"
 	"strings"
 
+	"sigs.k8s.io/kustomize/api/types"
+
 	"sigs.k8s.io/kustomize/api/filesys"
 	"sigs.k8s.io/kustomize/kustomize/v3/internal/commands/util"
 )
@@ -22,6 +24,8 @@ type flagsAndArgs struct {
 	// EnvFileSource to derive the configMap/Secret from (optional)
 	// TODO: Rationalize this name with Generic.EnvSource
 	EnvFileSource string
+	// Resource generation behavior (optional)
+	Behavior string
 	// Type of secret to create
 	Type string
 	// Namespace of secret
@@ -42,6 +46,10 @@ func (a *flagsAndArgs) Validate(args []string) error {
 	if len(a.EnvFileSource) > 0 && (len(a.FileSources) > 0 || len(a.LiteralSources) > 0) {
 		return fmt.Errorf("from-env-file cannot be combined with from-file or from-literal")
 	}
+	if len(a.Behavior) > 0 && types.NewGenerationBehavior(a.Behavior) == types.BehaviorUnspecified {
+		return fmt.Errorf(`invalid behavior: must be one of "%s", "%s", or "%s"`,
+			types.BehaviorCreate, types.BehaviorMerge, types.BehaviorReplace)
+	}
 	// TODO: Should we check if the path exists? if it's valid, if it's within the same (sub-)directory?
 	return nil
 }

kustomize/internal/commands/edit/add/flagsandargs_test.go

@@ -61,6 +61,22 @@ func TestDataConfigValidation_Flags(t *testing.T) {
 			},
 			shouldFail: false,
 		},
+		{
+			name: "correct behavior",
+			fa: flagsAndArgs{
+				EnvFileSource: "foo",
+				Behavior:      "merge",
+			},
+			shouldFail: false,
+		},
+		{
+			name: "incorrect behavior",
+			fa: flagsAndArgs{
+				EnvFileSource: "foo",
+				Behavior:      "merge-unknown",
+			},
+			shouldFail: true,
+		},
 	}
 
 	for _, test := range tests {

kustomize/internal/commands/edit/add/secret.go

@@ -149,4 +149,7 @@ func mergeFlagsIntoGeneratorArgs(args *types.GeneratorArgs, flags flagsAndArgs)
 			DisableNameSuffixHash: true,
 		}
 	}
+	if flags.Behavior != "" {
+		args.Behavior = flags.Behavior
+	}
 }