Add 'one required flag' group

completions_test.go

@@ -2830,6 +2830,104 @@ func TestCompletionForGroupedFlags(t *testing.T) {
 	}
 }
 
+func TestCompletionForOneRequiredGroupFlags(t *testing.T) {
+	getCmd := func() *Command {
+		rootCmd := &Command{
+			Use: "root",
+			Run: emptyRun,
+		}
+		childCmd := &Command{
+			Use: "child",
+			ValidArgsFunction: func(cmd *Command, args []string, toComplete string) ([]string, ShellCompDirective) {
+				return []string{"subArg"}, ShellCompDirectiveNoFileComp
+			},
+			Run: emptyRun,
+		}
+		rootCmd.AddCommand(childCmd)
+
+		rootCmd.PersistentFlags().Int("ingroup1", -1, "ingroup1")
+		rootCmd.PersistentFlags().String("ingroup2", "", "ingroup2")
+
+		childCmd.Flags().Bool("ingroup3", false, "ingroup3")
+		childCmd.Flags().Bool("nogroup", false, "nogroup")
+
+		// Add flags to a group
+		childCmd.MarkFlagsOneRequired("ingroup1", "ingroup2", "ingroup3")
+
+		return rootCmd
+	}
+
+	// Each test case uses a unique command from the function above.
+	testcases := []struct {
+		desc           string
+		args           []string
+		expectedOutput string
+	}{
+		{
+			desc: "flags in group suggested without - prefix",
+			args: []string{"child", ""},
+			expectedOutput: strings.Join([]string{
+				"--ingroup1",
+				"--ingroup2",
+				"--ingroup3",
+				"subArg",
+				":4",
+				"Completion ended with directive: ShellCompDirectiveNoFileComp", ""}, "\n"),
+		},
+		{
+			desc: "flags in group suggested with - prefix",
+			args: []string{"child", "-"},
+			expectedOutput: strings.Join([]string{
+				"--ingroup1",
+				"--ingroup2",
+				"--ingroup3",
+				":4",
+				"Completion ended with directive: ShellCompDirectiveNoFileComp", ""}, "\n"),
+		},
+		{
+			desc: "when any flag in group present, other flags in group not suggested without - prefix",
+			args: []string{"child", "--ingroup2", "value", ""},
+			expectedOutput: strings.Join([]string{
+				"subArg",
+				":4",
+				"Completion ended with directive: ShellCompDirectiveNoFileComp", ""}, "\n"),
+		},
+		{
+			desc: "when all flags in group present, flags not suggested without - prefix",
+			args: []string{"child", "--ingroup1", "8", "--ingroup2", "value2", "--ingroup3", ""},
+			expectedOutput: strings.Join([]string{
+				"subArg",
+				":4",
+				"Completion ended with directive: ShellCompDirectiveNoFileComp", ""}, "\n"),
+		},
+		{
+			desc: "group ignored if some flags not applicable",
+			args: []string{"--ingroup2", "value", ""},
+			expectedOutput: strings.Join([]string{
+				"child",
+				"completion",
+				"help",
+				":4",
+				"Completion ended with directive: ShellCompDirectiveNoFileComp", ""}, "\n"),
+		},
+	}
+
+	for _, tc := range testcases {
+		t.Run(tc.desc, func(t *testing.T) {
+			c := getCmd()
+			args := []string{ShellCompNoDescRequestCmd}
+			args = append(args, tc.args...)
+			output, err := executeCommand(c, args...)
+			switch {
+			case err == nil && output != tc.expectedOutput:
+				t.Errorf("expected: %q, got: %q", tc.expectedOutput, output)
+			case err != nil:
+				t.Errorf("Unexpected error %q", err)
+			}
+		})
+	}
+}
+
 func TestCompletionForMutuallyExclusiveFlags(t *testing.T) {
 	getCmd := func() *Command {
 		rootCmd := &Command{

flag_groups.go

@@ -24,6 +24,7 @@ import (
 
 const (
 	requiredAsGroup   = "cobra_annotation_required_if_others_set"
+	oneRequired       = "cobra_annotation_one_required"
 	mutuallyExclusive = "cobra_annotation_mutually_exclusive"
 )
 
@@ -43,6 +44,22 @@ func (c *Command) MarkFlagsRequiredTogether(flagNames ...string) {
 	}
 }
 
+// MarkFlagsOneRequired marks the given flags with annotations so that Cobra errors
+// if the command is invoked without at least one flag from the given set of flags.
+func (c *Command) MarkFlagsOneRequired(flagNames ...string) {
+	c.mergePersistentFlags()
+	for _, v := range flagNames {
+		f := c.Flags().Lookup(v)
+		if f == nil {
+			panic(fmt.Sprintf("Failed to find flag %q and mark it as being in a one-required flag group", v))
+		}
+		if err := c.Flags().SetAnnotation(v, oneRequired, append(f.Annotations[oneRequired], strings.Join(flagNames, " "))); err != nil {
+			// Only errs if the flag isn't found.
+			panic(err)
+		}
+	}
+}
+
 // MarkFlagsMutuallyExclusive marks the given flags with annotations so that Cobra errors
 // if the command is invoked with more than one flag from the given set of flags.
 func (c *Command) MarkFlagsMutuallyExclusive(flagNames ...string) {
@@ -59,7 +76,7 @@ func (c *Command) MarkFlagsMutuallyExclusive(flagNames ...string) {
 	}
 }
 
-// ValidateFlagGroups validates the mutuallyExclusive/requiredAsGroup logic and returns the
+// ValidateFlagGroups validates the mutuallyExclusive/oneRequired/requiredAsGroup logic and returns the
 // first error encountered.
 func (c *Command) ValidateFlagGroups() error {
 	if c.DisableFlagParsing {
@@ -71,15 +88,20 @@ func (c *Command) ValidateFlagGroups() error {
 	// groupStatus format is the list of flags as a unique ID,
 	// then a map of each flag name and whether it is set or not.
 	groupStatus := map[string]map[string]bool{}
+	oneRequiredGroupStatus := map[string]map[string]bool{}
 	mutuallyExclusiveGroupStatus := map[string]map[string]bool{}
 	flags.VisitAll(func(pflag *flag.Flag) {
 		processFlagForGroupAnnotation(flags, pflag, requiredAsGroup, groupStatus)
+		processFlagForGroupAnnotation(flags, pflag, oneRequired, oneRequiredGroupStatus)
 		processFlagForGroupAnnotation(flags, pflag, mutuallyExclusive, mutuallyExclusiveGroupStatus)
 	})
 
 	if err := validateRequiredFlagGroups(groupStatus); err != nil {
 		return err
 	}
+	if err := validateOneRequiredFlagGroups(oneRequiredGroupStatus); err != nil {
+		return err
+	}
 	if err := validateExclusiveFlagGroups(mutuallyExclusiveGroupStatus); err != nil {
 		return err
 	}
@@ -142,6 +164,27 @@ func validateRequiredFlagGroups(data map[string]map[string]bool) error {
 	return nil
 }
 
+func validateOneRequiredFlagGroups(data map[string]map[string]bool) error {
+	keys := sortedKeys(data)
+	for _, flagList := range keys {
+		flagnameAndStatus := data[flagList]
+		var set []string
+		for flagname, isSet := range flagnameAndStatus {
+			if isSet {
+				set = append(set, flagname)
+			}
+		}
+		if len(set) >= 1 {
+			continue
+		}
+
+		// Sort values, so they can be tested/scripted against consistently.
+		sort.Strings(set)
+		return fmt.Errorf("at least one of the flags in the group [%v] is required", flagList)
+	}
+	return nil
+}
+
 func validateExclusiveFlagGroups(data map[string]map[string]bool) error {
 	keys := sortedKeys(data)
 	for _, flagList := range keys {
@@ -176,6 +219,7 @@ func sortedKeys(m map[string]map[string]bool) []string {
 
 // enforceFlagGroupsForCompletion will do the following:
 // - when a flag in a group is present, other flags in the group will be marked required
+// - when none of the flags in a one-required group are present, all flags in the group will be marked required
 // - when a flag in a mutually exclusive group is present, other flags in the group will be marked as hidden
 // This allows the standard completion logic to behave appropriately for flag groups
 func (c *Command) enforceFlagGroupsForCompletion() {
@@ -185,9 +229,11 @@ func (c *Command) enforceFlagGroupsForCompletion() {
 
 	flags := c.Flags()
 	groupStatus := map[string]map[string]bool{}
+	oneRequiredGroupStatus := map[string]map[string]bool{}
 	mutuallyExclusiveGroupStatus := map[string]map[string]bool{}
 	c.Flags().VisitAll(func(pflag *flag.Flag) {
 		processFlagForGroupAnnotation(flags, pflag, requiredAsGroup, groupStatus)
+		processFlagForGroupAnnotation(flags, pflag, oneRequired, oneRequiredGroupStatus)
 		processFlagForGroupAnnotation(flags, pflag, mutuallyExclusive, mutuallyExclusiveGroupStatus)
 	})
 
@@ -204,6 +250,26 @@ func (c *Command) enforceFlagGroupsForCompletion() {
 		}
 	}
 
+	// If none of the flags of a one-required group are present, we make all the flags
+	// of that group required so that the shell completion suggests them automatically
+	for flagList, flagnameAndStatus := range oneRequiredGroupStatus {
+		set := 0
+
+		for _, isSet := range flagnameAndStatus {
+			if isSet {
+				set++
+			}
+		}
+
+		// None of the flags of the group are set, mark all flags in the group
+		// as required
+		if set == 0 {
+			for _, fName := range strings.Split(flagList, " ") {
+				_ = c.MarkFlagRequired(fName)
+			}
+		}
+	}
+
 	// If a flag that is mutually exclusive to others is present, we hide the other
 	// flags of that group so the shell completion does not suggest them
 	for flagList, flagnameAndStatus := range mutuallyExclusiveGroupStatus {

flag_groups_test.go

@@ -43,13 +43,15 @@ func TestValidateFlagGroups(t *testing.T) {
 
 	// Each test case uses a unique command from the function above.
 	testcases := []struct {
-		desc                      string
-		flagGroupsRequired        []string
-		flagGroupsExclusive       []string
-		subCmdFlagGroupsRequired  []string
-		subCmdFlagGroupsExclusive []string
-		args                      []string
-		expectErr                 string
+		desc                        string
+		flagGroupsRequired          []string
+		flagGroupsOneRequired       []string
+		flagGroupsExclusive         []string
+		subCmdFlagGroupsRequired    []string
+		subCmdFlagGroupsOneRequired []string
+		subCmdFlagGroupsExclusive   []string
+		args                        []string
+		expectErr                   string
 	}{
 		{
 			desc: "No flags no problem",
@@ -62,6 +64,11 @@ func TestValidateFlagGroups(t *testing.T) {
 			flagGroupsRequired: []string{"a b c"},
 			args:               []string{"--a=foo"},
 			expectErr:          "if any flags in the group [a b c] are set they must all be set; missing [b c]",
+		}, {
+			desc:                  "One-required flag group not satisfied",
+			flagGroupsOneRequired: []string{"a b"},
+			args:                  []string{"--c=foo"},
+			expectErr:             "at least one of the flags in the group [a b] is required",
 		}, {
 			desc:                "Exclusive flag group not satisfied",
 			flagGroupsExclusive: []string{"a b c"},
@@ -72,6 +79,11 @@ func TestValidateFlagGroups(t *testing.T) {
 			flagGroupsRequired: []string{"a b c", "a d"},
 			args:               []string{"--c=foo", "--d=foo"},
 			expectErr:          `if any flags in the group [a b c] are set they must all be set; missing [a b]`,
+		}, {
+			desc:                  "Multiple one-required flag group not satisfied returns first error",
+			flagGroupsOneRequired: []string{"a b", "d e"},
+			args:                  []string{"--c=foo", "--f=foo"},
+			expectErr:             `at least one of the flags in the group [a b] is required`,
 		}, {
 			desc:                "Multiple exclusive flag group not satisfied returns first error",
 			flagGroupsExclusive: []string{"a b c", "a d"},
@@ -82,32 +94,57 @@ func TestValidateFlagGroups(t *testing.T) {
 			flagGroupsRequired: []string{"a d", "a b", "a c"},
 			args:               []string{"--a=foo"},
 			expectErr:          `if any flags in the group [a b] are set they must all be set; missing [b]`,
+		}, {
+			desc:                  "Validation of one-required groups occurs on groups in sorted order",
+			flagGroupsOneRequired: []string{"d e", "a b", "f g"},
+			args:                  []string{"--c=foo"},
+			expectErr:             `at least one of the flags in the group [a b] is required`,
 		}, {
 			desc:                "Validation of exclusive groups occurs on groups in sorted order",
 			flagGroupsExclusive: []string{"a d", "a b", "a c"},
 			args:                []string{"--a=foo", "--b=foo", "--c=foo"},
 			expectErr:           `if any flags in the group [a b] are set none of the others can be; [a b] were all set`,
 		}, {
-			desc:                "Persistent flags utilize both features and can fail required groups",
+			desc:                "Persistent flags utilize required and exclusive groups and can fail required groups",
 			flagGroupsRequired:  []string{"a e", "e f"},
 			flagGroupsExclusive: []string{"f g"},
 			args:                []string{"--a=foo", "--f=foo", "--g=foo"},
 			expectErr:           `if any flags in the group [a e] are set they must all be set; missing [e]`,
 		}, {
-			desc:                "Persistent flags utilize both features and can fail mutually exclusive groups",
+			desc:                  "Persistent flags utilize one-required and exclusive groups and can fail one-required groups",
+			flagGroupsOneRequired: []string{"a b", "e f"},
+			flagGroupsExclusive:   []string{"e f"},
+			args:                  []string{"--e=foo"},
+			expectErr:             `at least one of the flags in the group [a b] is required`,
+		}, {
+			desc:                "Persistent flags utilize required and exclusive groups and can fail mutually exclusive groups",
 			flagGroupsRequired:  []string{"a e", "e f"},
 			flagGroupsExclusive: []string{"f g"},
 			args:                []string{"--a=foo", "--e=foo", "--f=foo", "--g=foo"},
 			expectErr:           `if any flags in the group [f g] are set none of the others can be; [f g] were all set`,
 		}, {
-			desc:                "Persistent flags utilize both features and can pass",
+			desc:                "Persistent flags utilize required and exclusive groups and can pass",
 			flagGroupsRequired:  []string{"a e", "e f"},
 			flagGroupsExclusive: []string{"f g"},
 			args:                []string{"--a=foo", "--e=foo", "--f=foo"},
+		}, {
+			desc:                  "Persistent flags utilize one-required and exclusive groups and can pass",
+			flagGroupsOneRequired: []string{"a e", "e f"},
+			flagGroupsExclusive:   []string{"f g"},
+			args:                  []string{"--a=foo", "--e=foo", "--f=foo"},
 		}, {
 			desc:                     "Subcmds can use required groups using inherited flags",
 			subCmdFlagGroupsRequired: []string{"e subonly"},
 			args:                     []string{"subcmd", "--e=foo", "--subonly=foo"},
+		}, {
+			desc:                        "Subcmds can use one-required groups using inherited flags",
+			subCmdFlagGroupsOneRequired: []string{"e subonly"},
+			args:                        []string{"subcmd", "--e=foo", "--subonly=foo"},
+		}, {
+			desc:                        "Subcmds can use one-required groups using inherited flags and fail one-required groups",
+			subCmdFlagGroupsOneRequired: []string{"e subonly"},
+			args:                        []string{"subcmd"},
+			expectErr:                   "at least one of the flags in the group [e subonly] is required",
 		}, {
 			desc:                      "Subcmds can use exclusive groups using inherited flags",
 			subCmdFlagGroupsExclusive: []string{"e subonly"},
@@ -130,12 +167,18 @@ func TestValidateFlagGroups(t *testing.T) {
 			for _, flagGroup := range tc.flagGroupsRequired {
 				c.MarkFlagsRequiredTogether(strings.Split(flagGroup, " ")...)
 			}
+			for _, flagGroup := range tc.flagGroupsOneRequired {
+				c.MarkFlagsOneRequired(strings.Split(flagGroup, " ")...)
+			}
 			for _, flagGroup := range tc.flagGroupsExclusive {
 				c.MarkFlagsMutuallyExclusive(strings.Split(flagGroup, " ")...)
 			}
 			for _, flagGroup := range tc.subCmdFlagGroupsRequired {
 				sub.MarkFlagsRequiredTogether(strings.Split(flagGroup, " ")...)
 			}
+			for _, flagGroup := range tc.subCmdFlagGroupsOneRequired {
+				sub.MarkFlagsOneRequired(strings.Split(flagGroup, " ")...)
+			}
 			for _, flagGroup := range tc.subCmdFlagGroupsExclusive {
 				sub.MarkFlagsMutuallyExclusive(strings.Split(flagGroup, " ")...)
 			}

site/content/user_guide.md

@@ -349,7 +349,16 @@ rootCmd.Flags().BoolVar(&ofYaml, "yaml", false, "Output in YAML")
 rootCmd.MarkFlagsMutuallyExclusive("json", "yaml")
 ```
 
-In both of these cases:
+If you want to require least one flag from a group to be present, you can use `MarkFlagsOneRequired`.
+This can be combined with `MarkFlagsMutuallyExclusive` to enforce exactly one flag from a given group:
+```go
+rootCmd.Flags().BoolVar(&ofJson, "json", false, "Output in JSON")
+rootCmd.Flags().BoolVar(&ofYaml, "yaml", false, "Output in YAML")
+rootCmd.MarkFlagsOneRequired("json", "yaml")
+rootCmd.MarkFlagsMutuallyExclusive("json", "yaml")
+```
+
+In these cases:
   - both local and persistent flags can be used
     - **NOTE:** the group is only enforced on commands where every flag is defined
   - a flag may appear in multiple groups