Can now update tag/style of nodes without affecting the value

cmd/new.go

@@ -2,6 +2,7 @@ package cmd
 
 import (
 	"github.com/mikefarah/yq/v3/pkg/yqlib"
+	errors "github.com/pkg/errors"
 	"github.com/spf13/cobra"
 )
 
@@ -32,7 +33,12 @@ Note that you can give a create script to perform more sophisticated yaml. This
 }
 
 func newProperty(cmd *cobra.Command, args []string) error {
-	var updateCommands, updateCommandsError = readUpdateCommands(args, 2, "Must provide <path_to_update> <value>")
+	var badArgsMessage = "Must provide <path_to_update> <value>"
+	if len(args) != 2 {
+		return errors.New(badArgsMessage)
+	}
+
+	var updateCommands, updateCommandsError = readUpdateCommands(args, 2, badArgsMessage)
 	if updateCommandsError != nil {
 		return updateCommandsError
 	}

cmd/utils.go

@@ -430,15 +430,20 @@ func readUpdateCommands(args []string, expectedArgs int, badArgsMessage string)
 		log.Debug("args %v", args[expectedArgs-2])
 		updateCommands = make([]yqlib.UpdateCommand, 1)
 		updateCommands[0] = yqlib.UpdateCommand{Command: "update", Path: args[expectedArgs-2], Value: value.Content[0], Overwrite: true}
-
-	} else if len(args) < expectedArgs {
-		return nil, errors.New(badArgsMessage)
-	} else {
+	} else if len(args) == expectedArgs {
 		updateCommands = make([]yqlib.UpdateCommand, 1)
 		log.Debug("args %v", args)
 		log.Debug("path %v", args[expectedArgs-2])
 		log.Debug("Value %v", args[expectedArgs-1])
 		updateCommands[0] = yqlib.UpdateCommand{Command: "update", Path: args[expectedArgs-2], Value: valueParser.Parse(args[expectedArgs-1], customTag, customStyle), Overwrite: true}
+	} else if len(args) == expectedArgs-1 {
+		// don't update the value
+		updateCommands = make([]yqlib.UpdateCommand, 1)
+		log.Debug("args %v", args)
+		log.Debug("path %v", args[expectedArgs-2])
+		updateCommands[0] = yqlib.UpdateCommand{Command: "update", Path: args[expectedArgs-2], Value: valueParser.Parse("", customTag, customStyle), Overwrite: true, DontUpdateNodeValue: true}
+	} else {
+		return nil, errors.New(badArgsMessage)
 	}
 	return updateCommands, nil
 }

cmd/write_test.go

@@ -63,6 +63,46 @@ func TestWriteWithDoubleQuotedStyleCmd(t *testing.T) {
 	test.AssertResult(t, expectedOutput, result.Output)
 }
 
+func TestWriteUpdateStyleOnlyCmd(t *testing.T) {
+	content := `b:
+  c: dog
+  d: things
+`
+	filename := test.WriteTempYamlFile(content)
+	defer test.RemoveTempYamlFile(filename)
+
+	cmd := getRootCommand()
+	result := test.RunCmd(cmd, fmt.Sprintf("write %s b.* --style=single", filename))
+	if result.Error != nil {
+		t.Error(result.Error)
+	}
+	expectedOutput := `b:
+  c: 'dog'
+  d: 'things'
+`
+	test.AssertResult(t, expectedOutput, result.Output)
+}
+
+func TestWriteUpdateTagOnlyCmd(t *testing.T) {
+	content := `b:
+  c: true
+  d: false
+`
+	filename := test.WriteTempYamlFile(content)
+	defer test.RemoveTempYamlFile(filename)
+
+	cmd := getRootCommand()
+	result := test.RunCmd(cmd, fmt.Sprintf("write %s b.* --tag=!!str", filename))
+	if result.Error != nil {
+		t.Error(result.Error)
+	}
+	expectedOutput := `b:
+  c: "true"
+  d: "false"
+`
+	test.AssertResult(t, expectedOutput, result.Output)
+}
+
 func TestWriteWithSingleQuotedStyleCmd(t *testing.T) {
 	content := `b:
   c: dog

pkg/yqlib/lib.go

@@ -13,10 +13,11 @@ import (
 var log = logging.MustGetLogger("yq")
 
 type UpdateCommand struct {
-	Command   string
-	Path      string
-	Value     *yaml.Node
-	Overwrite bool
+	Command             string
+	Path                string
+	Value               *yaml.Node
+	Overwrite           bool
+	DontUpdateNodeValue bool
 }
 
 func KindString(kind yaml.Kind) string {

pkg/yqlib/update_navigation_strategy.go

@@ -21,7 +21,9 @@ func UpdateNavigationStrategy(updateCommand UpdateCommand, autoCreate bool) Navi
 				DebugNode(node)
 				log.Debug("with")
 				DebugNode(changesToApply)
-				node.Value = changesToApply.Value
+				if !updateCommand.DontUpdateNodeValue {
+					node.Value = changesToApply.Value
+				}
 				node.Tag = changesToApply.Tag
 				node.Kind = changesToApply.Kind
 				node.Style = changesToApply.Style