improve fields format: support deltas via +/-

cmd/base/flags.go

@@ -15,7 +15,7 @@ func AddGlobalFlags(cmd *cobra.Command) {
 }
 
 func AddFormatFlags(cmd *cobra.Command) {
-	cmd.PersistentFlags().StringArrayP("field", "f", []string{}, "output only these fields, can be specified multiple times")
+	cmd.PersistentFlags().StringArrayP("field", "f", []string{}, "output only these fields, can be specified multiple times; prefix with + or - to add/remove from the default fields instead of replacing them")
 	cmd.PersistentFlags().Bool("field-list", false, "list available fields")
 	cmd.PersistentFlags().Bool("page-view", false, "use page view format")
 	cmd.PersistentFlags().StringP("template", "t", "", "go template string to output in specified format")

cmd/base/hooks.go

@@ -114,6 +114,9 @@ func CheckFormatterFlags(cmdContext *CmdContext, entities map[string]entities.En
 			return err
 		}
 		if len(fields) > 0 {
+			if err := validateFieldPrefixConsistency(fields); err != nil {
+				return err
+			}
 			if err := entity.Validate(fields); err != nil {
 				return err
 			}
@@ -123,6 +126,22 @@ func CheckFormatterFlags(cmdContext *CmdContext, entities map[string]entities.En
 	}
 }
 
+// validateFieldPrefixConsistency ensures +/- prefixed field names (add/remove
+// relative to the default set) are not mixed with plain field names
+// (full replacement) in the same --field invocation.
+func validateFieldPrefixConsistency(fields []string) error {
+	prefixed := 0
+	for _, f := range fields {
+		if entities.HasFieldPrefix(f) {
+			prefixed++
+		}
+	}
+	if prefixed > 0 && prefixed != len(fields) {
+		return fmt.Errorf("cannot mix plain field names with +/- prefixed field names in --field")
+	}
+	return nil
+}
+
 // CheckEmptyContexts returns error if no contexts found
 func CheckEmptyContexts(cmdContext *CmdContext) func(cmd *cobra.Command, args []string) error {
 	return func(cmd *cobra.Command, args []string) error {

cmd/base/hooks_test.go

@@ -0,0 +1,16 @@
+package base
+
+import (
+	"testing"
+
+	. "github.com/onsi/gomega"
+)
+
+func TestValidateFieldPrefixConsistency(t *testing.T) {
+	g := NewWithT(t)
+
+	g.Expect(validateFieldPrefixConsistency([]string{"Name", "Fingerprint"})).To(BeNil())
+	g.Expect(validateFieldPrefixConsistency([]string{"+Name", "-Fingerprint"})).To(BeNil())
+	g.Expect(validateFieldPrefixConsistency([]string{"Name", "+Fingerprint"})).To(HaveOccurred())
+	g.Expect(validateFieldPrefixConsistency([]string{"+Name", "Fingerprint"})).To(HaveOccurred())
+}

internal/output/entities/interface.go

@@ -113,14 +113,17 @@ func (e *Entity) GetFields() []Field {
 	return e.fields
 }
 
-// Validate checks that all fields match available ones
+// Validate checks that all fields match available ones. A leading +/-
+// prefix (used to add/remove a field relative to the default set) is
+// stripped before matching.
 func (e *Entity) Validate(fields []string) error {
 	availableFields := e.GetFields()
 
 	for _, f := range fields {
+		id := StripFieldPrefix(f)
 		found := false
 		for _, af := range availableFields {
-			if af.ID == f || e.fieldInChildFields(af.ChildFields, f) {
+			if af.ID == id || e.fieldInChildFields(af.ChildFields, id) {
 				found = true
 				break
 			}
@@ -133,6 +136,21 @@ func (e *Entity) Validate(fields []string) error {
 	return nil
 }
 
+// HasFieldPrefix reports whether the field name is prefixed with + or -,
+// meaning it should be added to/removed from the default field set
+// instead of replacing it outright.
+func HasFieldPrefix(name string) bool {
+	return len(name) > 0 && (name[0] == '+' || name[0] == '-')
+}
+
+// StripFieldPrefix removes a leading +/- prefix from a field name, if present.
+func StripFieldPrefix(name string) string {
+	if HasFieldPrefix(name) {
+		return name[1:]
+	}
+	return name
+}
+
 // GetCmdDefaultFields returns the default field IDs to show for the given
 // command. If the command has an explicit set in cmdDefaultFields it is returned, otherwise it
 // falls back to the registration-time defaults (fields marked Field.Default).

internal/output/entities/interface_test.go

@@ -0,0 +1,36 @@
+package entities
+
+import (
+	"testing"
+
+	. "github.com/onsi/gomega"
+	serverscom "github.com/serverscom/serverscom-go-client/pkg"
+)
+
+func TestHasFieldPrefix(t *testing.T) {
+	g := NewWithT(t)
+
+	g.Expect(HasFieldPrefix("+Name")).To(BeTrue())
+	g.Expect(HasFieldPrefix("-Name")).To(BeTrue())
+	g.Expect(HasFieldPrefix("Name")).To(BeFalse())
+	g.Expect(HasFieldPrefix("")).To(BeFalse())
+}
+
+func TestStripFieldPrefix(t *testing.T) {
+	g := NewWithT(t)
+
+	g.Expect(StripFieldPrefix("+Name")).To(Equal("Name"))
+	g.Expect(StripFieldPrefix("-Name")).To(Equal("Name"))
+	g.Expect(StripFieldPrefix("Name")).To(Equal("Name"))
+}
+
+func TestEntityValidateWithFieldPrefix(t *testing.T) {
+	g := NewWithT(t)
+
+	entity, err := Registry.GetEntityFromValue(serverscom.SSHKey{})
+	g.Expect(err).To(BeNil())
+
+	g.Expect(entity.Validate([]string{"+Fingerprint"})).To(BeNil())
+	g.Expect(entity.Validate([]string{"-Name"})).To(BeNil())
+	g.Expect(entity.Validate([]string{"+Unknown"})).To(HaveOccurred())
+}

internal/output/utils.go

@@ -43,6 +43,9 @@ func (f *Formatter) printField(w *tabwriter.Writer, field entities.Field) {
 // getOrderedFields returns ordered fields based on the configuration.
 // Returns default fields if no fieldsToShow are provided for list mode.
 // Returns all available fields if no fieldsToShow are provided for page-view mode.
+// If fieldsToShow are +/- prefixed, they are applied as additions/removals to
+// the command's default fields instead of replacing them outright; this is a
+// no-op in page-view mode, which always shows all fields.
 func (f *Formatter) getOrderedFields(entity entities.EntityInterface) []entities.Field {
 	fieldsToShow := f.fieldsToShow
 
@@ -51,6 +54,11 @@ func (f *Formatter) getOrderedFields(entity entities.EntityInterface) []entities
 			return entity.GetFields()
 		}
 		fieldsToShow = entity.GetCmdDefaultFields(f.cmdName)
+	} else if entities.HasFieldPrefix(fieldsToShow[0]) {
+		if f.pageView {
+			return entity.GetFields()
+		}
+		fieldsToShow = applyFieldDeltas(entity.GetCmdDefaultFields(f.cmdName), fieldsToShow)
 	}
 
 	availableFields := entity.GetFields()
@@ -65,6 +73,34 @@ func (f *Formatter) getOrderedFields(entity entities.EntityInterface) []entities
 	return orderedFields
 }
 
+// applyFieldDeltas applies +/- prefixed field deltas on top of the base
+// field list, preserving the base order and appending additions at the end
+// in the order they were given.
+func applyFieldDeltas(base []string, deltas []string) []string {
+	result := append([]string{}, base...)
+
+	for _, d := range deltas {
+		id := entities.StripFieldPrefix(d)
+		idx := -1
+		for i, existing := range result {
+			if existing == id {
+				idx = i
+				break
+			}
+		}
+
+		if d[0] == '-' {
+			if idx >= 0 {
+				result = append(result[:idx], result[idx+1:]...)
+			}
+		} else if idx < 0 {
+			result = append(result, id)
+		}
+	}
+
+	return result
+}
+
 // findFieldByID recursively finds a field by its ID in the given fields slice.
 func (f *Formatter) findFieldByID(fields []entities.Field, fieldID string) *entities.Field {
 	for _, field := range fields {

internal/output/utils_test.go

@@ -0,0 +1,76 @@
+package output
+
+import (
+	"testing"
+
+	. "github.com/onsi/gomega"
+	serverscom "github.com/serverscom/serverscom-go-client/pkg"
+	"github.com/serverscom/srvctl/internal/output/entities"
+)
+
+func sshKeyEntity(g *WithT) entities.EntityInterface {
+	entity, err := entities.Registry.GetEntityFromValue(serverscom.SSHKey{})
+	g.Expect(err).To(BeNil())
+	return entity
+}
+
+func fieldIDs(fields []entities.Field) []string {
+	ids := make([]string, 0, len(fields))
+	for _, f := range fields {
+		ids = append(ids, f.ID)
+	}
+	return ids
+}
+
+func TestGetOrderedFieldsPlain(t *testing.T) {
+	g := NewWithT(t)
+	entity := sshKeyEntity(g)
+
+	f := &Formatter{cmdName: "list"}
+	g.Expect(fieldIDs(f.getOrderedFields(entity))).To(Equal([]string{"Name", "Fingerprint"}))
+
+	f = &Formatter{cmdName: "list", fieldsToShow: []string{"Fingerprint"}}
+	g.Expect(fieldIDs(f.getOrderedFields(entity))).To(Equal([]string{"Fingerprint"}))
+}
+
+func TestGetOrderedFieldsAdd(t *testing.T) {
+	g := NewWithT(t)
+	entity := sshKeyEntity(g)
+
+	f := &Formatter{cmdName: "list", fieldsToShow: []string{"+Created"}}
+	g.Expect(fieldIDs(f.getOrderedFields(entity))).To(Equal([]string{"Name", "Fingerprint", "Created"}))
+}
+
+func TestGetOrderedFieldsRemove(t *testing.T) {
+	g := NewWithT(t)
+	entity := sshKeyEntity(g)
+
+	f := &Formatter{cmdName: "list", fieldsToShow: []string{"-Fingerprint"}}
+	g.Expect(fieldIDs(f.getOrderedFields(entity))).To(Equal([]string{"Name"}))
+}
+
+func TestGetOrderedFieldsAddAndRemove(t *testing.T) {
+	g := NewWithT(t)
+	entity := sshKeyEntity(g)
+
+	f := &Formatter{cmdName: "list", fieldsToShow: []string{"+Created", "-Fingerprint"}}
+	g.Expect(fieldIDs(f.getOrderedFields(entity))).To(Equal([]string{"Name", "Created"}))
+}
+
+func TestGetOrderedFieldsAddIgnoredInPageView(t *testing.T) {
+	g := NewWithT(t)
+	entity := sshKeyEntity(g)
+
+	f := &Formatter{cmdName: "list", pageView: true, fieldsToShow: []string{"+Created"}}
+	g.Expect(fieldIDs(f.getOrderedFields(entity))).To(Equal(fieldIDs(entity.GetFields())))
+}
+
+func TestApplyFieldDeltas(t *testing.T) {
+	g := NewWithT(t)
+
+	g.Expect(applyFieldDeltas([]string{"A", "B"}, []string{"+C"})).To(Equal([]string{"A", "B", "C"}))
+	g.Expect(applyFieldDeltas([]string{"A", "B"}, []string{"-A"})).To(Equal([]string{"B"}))
+	g.Expect(applyFieldDeltas([]string{"A", "B"}, []string{"+B"})).To(Equal([]string{"A", "B"}))
+	g.Expect(applyFieldDeltas([]string{"A", "B"}, []string{"-C"})).To(Equal([]string{"A", "B"}))
+	g.Expect(applyFieldDeltas([]string{"A", "B"}, []string{"-A", "+A"})).To(Equal([]string{"B", "A"}))
+}