feat: add CompletionWithDesc helper (#2231)

The code has also been refactored to use a type alias for completion and a completion helper

Using a type alias is a non-breaking change and it makes the code more readable and easier to understand.

Signed-off-by: ccoVeille <3875889+ccoVeille@users.noreply.github.com>
Co-authored-by: Marc Khouzam <marc.khouzam@gmail.com>

active_help.go

@@ -35,7 +35,7 @@ const (
 // This function can be called multiple times before and/or after completions are added to
 // the array.  Each time this function is called with the same array, the new
 // ActiveHelp line will be shown below the previous ones when completion is triggered.
-func AppendActiveHelp(compArray []string, activeHelpStr string) []string {
+func AppendActiveHelp(compArray []Completion, activeHelpStr string) []Completion {
 	return append(compArray, fmt.Sprintf("%s%s", activeHelpMarker, activeHelpStr))
 }
 

command.go

@@ -82,7 +82,7 @@ type Command struct {
 	Example string
 
 	// ValidArgs is list of all valid non-flag arguments that are accepted in shell completions
-	ValidArgs []string
+	ValidArgs []Completion
 	// ValidArgsFunction is an optional function that provides valid non-flag arguments for shell completion.
 	// It is a dynamic version of using ValidArgs.
 	// Only one of ValidArgs and ValidArgsFunction can be used for a command.
@@ -1272,8 +1272,8 @@ func (c *Command) InitDefaultHelpCmd() {
 			Short: "Help about any command",
 			Long: `Help provides help for any command in the application.
 Simply type ` + c.DisplayName() + ` help [path to command] for full details.`,
-			ValidArgsFunction: func(c *Command, args []string, toComplete string) ([]string, ShellCompDirective) {
-				var completions []string
+			ValidArgsFunction: func(c *Command, args []string, toComplete string) ([]Completion, ShellCompDirective) {
+				var completions []Completion
 				cmd, _, e := c.Root().Find(args)
 				if e != nil {
 					return nil, ShellCompDirectiveNoFileComp
@@ -1285,7 +1285,7 @@ Simply type ` + c.DisplayName() + ` help [path to command] for full details.`,
 				for _, subCmd := range cmd.Commands() {
 					if subCmd.IsAvailableCommand() || subCmd == cmd.helpCommand {
 						if strings.HasPrefix(subCmd.Name(), toComplete) {
-							completions = append(completions, fmt.Sprintf("%s\t%s", subCmd.Name(), subCmd.Short))
+							completions = append(completions, CompletionWithDesc(subCmd.Name(), subCmd.Short))
 						}
 					}
 				}

completions.go

@@ -117,15 +117,31 @@ type CompletionOptions struct {
 	HiddenDefaultCmd bool
 }
 
+// Completion is a string that can be used for completions
+//
+// two formats are supported:
+//   - the completion choice
+//   - the completion choice with a textual description (separated by a TAB).
+//
+// [CompletionWithDesc] can be used to create a completion string with a textual description.
+//
+// Note: Go type alias is used to provide a more descriptive name in the documentation, but any string can be used.
+type Completion = string
+
 // CompletionFunc is a function that provides completion results.
-type CompletionFunc func(cmd *Command, args []string, toComplete string) ([]string, ShellCompDirective)
+type CompletionFunc func(cmd *Command, args []string, toComplete string) ([]Completion, ShellCompDirective)
+
+// CompletionWithDesc returns a [Completion] with a description by using the TAB delimited format.
+func CompletionWithDesc(choice string, description string) Completion {
+	return choice + "\t" + description
+}
 
 // NoFileCompletions can be used to disable file completion for commands that should
 // not trigger file completions.
 //
 // This method satisfies [CompletionFunc].
 // It can be used with [Command.RegisterFlagCompletionFunc] and for [Command.ValidArgsFunction].
-func NoFileCompletions(cmd *Command, args []string, toComplete string) ([]string, ShellCompDirective) {
+func NoFileCompletions(cmd *Command, args []string, toComplete string) ([]Completion, ShellCompDirective) {
 	return nil, ShellCompDirectiveNoFileComp
 }
 
@@ -134,8 +150,8 @@ func NoFileCompletions(cmd *Command, args []string, toComplete string) ([]string
 //
 // This method returns a function that satisfies [CompletionFunc]
 // It can be used with [Command.RegisterFlagCompletionFunc] and for [Command.ValidArgsFunction].
-func FixedCompletions(choices []string, directive ShellCompDirective) CompletionFunc {
-	return func(cmd *Command, args []string, toComplete string) ([]string, ShellCompDirective) {
+func FixedCompletions(choices []Completion, directive ShellCompDirective) CompletionFunc {
+	return func(cmd *Command, args []string, toComplete string) ([]Completion, ShellCompDirective) {
 		return choices, directive
 	}
 }
@@ -290,7 +306,7 @@ type SliceValue interface {
 	GetSlice() []string
 }
 
-func (c *Command) getCompletions(args []string) (*Command, []string, ShellCompDirective, error) {
+func (c *Command) getCompletions(args []string) (*Command, []Completion, ShellCompDirective, error) {
 	// The last argument, which is not completely typed by the user,
 	// should not be part of the list of arguments
 	toComplete := args[len(args)-1]
@@ -318,7 +334,7 @@ func (c *Command) getCompletions(args []string) (*Command, []string, ShellCompDi
 	}
 	if err != nil {
 		// Unable to find the real command. E.g., <program> someInvalidCmd <TAB>
-		return c, []string{}, ShellCompDirectiveDefault, fmt.Errorf("unable to find a command for arguments: %v", trimmedArgs)
+		return c, []Completion{}, ShellCompDirectiveDefault, fmt.Errorf("unable to find a command for arguments: %v", trimmedArgs)
 	}
 	finalCmd.ctx = c.ctx
 
@@ -348,7 +364,7 @@ func (c *Command) getCompletions(args []string) (*Command, []string, ShellCompDi
 
 	// Parse the flags early so we can check if required flags are set
 	if err = finalCmd.ParseFlags(finalArgs); err != nil {
-		return finalCmd, []string{}, ShellCompDirectiveDefault, fmt.Errorf("Error while parsing flags from args %v: %s", finalArgs, err.Error())
+		return finalCmd, []Completion{}, ShellCompDirectiveDefault, fmt.Errorf("Error while parsing flags from args %v: %s", finalArgs, err.Error())
 	}
 
 	realArgCount := finalCmd.Flags().NArg()
@@ -360,14 +376,14 @@ func (c *Command) getCompletions(args []string) (*Command, []string, ShellCompDi
 	if flagErr != nil {
 		// If error type is flagCompError and we don't want flagCompletion we should ignore the error
 		if _, ok := flagErr.(*flagCompError); !(ok && !flagCompletion) {
-			return finalCmd, []string{}, ShellCompDirectiveDefault, flagErr
+			return finalCmd, []Completion{}, ShellCompDirectiveDefault, flagErr
 		}
 	}
 
 	// Look for the --help or --version flags.  If they are present,
 	// there should be no further completions.
 	if helpOrVersionFlagPresent(finalCmd) {
-		return finalCmd, []string{}, ShellCompDirectiveNoFileComp, nil
+		return finalCmd, []Completion{}, ShellCompDirectiveNoFileComp, nil
 	}
 
 	// We only remove the flags from the arguments if DisableFlagParsing is not set.
@@ -396,11 +412,11 @@ func (c *Command) getCompletions(args []string) (*Command, []string, ShellCompDi
 				return finalCmd, subDir, ShellCompDirectiveFilterDirs, nil
 			}
 			// Directory completion
-			return finalCmd, []string{}, ShellCompDirectiveFilterDirs, nil
+			return finalCmd, []Completion{}, ShellCompDirectiveFilterDirs, nil
 		}
 	}
 
-	var completions []string
+	var completions []Completion
 	var directive ShellCompDirective
 
 	// Enforce flag groups before doing flag completions
@@ -486,7 +502,7 @@ func (c *Command) getCompletions(args []string) (*Command, []string, ShellCompDi
 				for _, subCmd := range finalCmd.Commands() {
 					if subCmd.IsAvailableCommand() || subCmd == finalCmd.helpCommand {
 						if strings.HasPrefix(subCmd.Name(), toComplete) {
-							completions = append(completions, fmt.Sprintf("%s\t%s", subCmd.Name(), subCmd.Short))
+							completions = append(completions, CompletionWithDesc(subCmd.Name(), subCmd.Short))
 						}
 						directive = ShellCompDirectiveNoFileComp
 					}
@@ -542,7 +558,7 @@ func (c *Command) getCompletions(args []string) (*Command, []string, ShellCompDi
 	if completionFn != nil {
 		// Go custom completion defined for this flag or command.
 		// Call the registered completion function to get the completions.
-		var comps []string
+		var comps []Completion
 		comps, directive = completionFn(finalCmd, finalArgs, toComplete)
 		completions = append(completions, comps...)
 	}
@@ -562,16 +578,16 @@ func helpOrVersionFlagPresent(cmd *Command) bool {
 	return false
 }
 
-func getFlagNameCompletions(flag *pflag.Flag, toComplete string) []string {
+func getFlagNameCompletions(flag *pflag.Flag, toComplete string) []Completion {
 	if nonCompletableFlag(flag) {
-		return []string{}
+		return []Completion{}
 	}
 
-	var completions []string
+	var completions []Completion
 	flagName := "--" + flag.Name
 	if strings.HasPrefix(flagName, toComplete) {
 		// Flag without the =
-		completions = append(completions, fmt.Sprintf("%s\t%s", flagName, flag.Usage))
+		completions = append(completions, CompletionWithDesc(flagName, flag.Usage))
 
 		// Why suggest both long forms: --flag and --flag= ?
 		// This forces the user to *always* have to type either an = or a space after the flag name.
@@ -583,20 +599,20 @@ func getFlagNameCompletions(flag *pflag.Flag, toComplete string) []string {
 		// if len(flag.NoOptDefVal) == 0 {
 		// 	// Flag requires a value, so it can be suffixed with =
 		// 	flagName += "="
-		// 	completions = append(completions, fmt.Sprintf("%s\t%s", flagName, flag.Usage))
+		// 	completions = append(completions, CompletionWithDesc(flagName, flag.Usage))
 		// }
 	}
 
 	flagName = "-" + flag.Shorthand
 	if len(flag.Shorthand) > 0 && strings.HasPrefix(flagName, toComplete) {
-		completions = append(completions, fmt.Sprintf("%s\t%s", flagName, flag.Usage))
+		completions = append(completions, CompletionWithDesc(flagName, flag.Usage))
 	}
 
 	return completions
 }
 
-func completeRequireFlags(finalCmd *Command, toComplete string) []string {
-	var completions []string
+func completeRequireFlags(finalCmd *Command, toComplete string) []Completion {
+	var completions []Completion
 
 	doCompleteRequiredFlags := func(flag *pflag.Flag) {
 		if _, present := flag.Annotations[BashCompOneRequiredFlag]; present {

completions_test.go

@@ -2872,6 +2872,56 @@ func TestFixedCompletions(t *testing.T) {
 	}
 }
 
+func TestFixedCompletionsWithCompletionHelpers(t *testing.T) {
+	rootCmd := &Command{Use: "root", Args: NoArgs, Run: emptyRun}
+	// here we are mixing string, [Completion] and [CompletionWithDesc]
+	choices := []string{"apple", Completion("banana"), CompletionWithDesc("orange", "orange are orange")}
+	childCmd := &Command{
+		Use:               "child",
+		ValidArgsFunction: FixedCompletions(choices, ShellCompDirectiveNoFileComp),
+		Run:               emptyRun,
+	}
+	rootCmd.AddCommand(childCmd)
+
+	t.Run("completion with description", func(t *testing.T) {
+		output, err := executeCommand(rootCmd, ShellCompRequestCmd, "child", "a")
+		if err != nil {
+			t.Errorf("Unexpected error: %v", err)
+		}
+
+		expected := strings.Join([]string{
+			"apple",
+			"banana",
+			"orange\torange are orange", // this one has the description as expected with [ShellCompRequestCmd] flag
+			":4",
+			"Completion ended with directive: ShellCompDirectiveNoFileComp", "",
+		}, "\n")
+
+		if output != expected {
+			t.Errorf("expected: %q, got: %q", expected, output)
+		}
+	})
+
+	t.Run("completion with no description", func(t *testing.T) {
+		output, err := executeCommand(rootCmd, ShellCompNoDescRequestCmd, "child", "a")
+		if err != nil {
+			t.Errorf("Unexpected error: %v", err)
+		}
+
+		expected := strings.Join([]string{
+			"apple",
+			"banana",
+			"orange", // the description is absent as expected with [ShellCompNoDescRequestCmd] flag
+			":4",
+			"Completion ended with directive: ShellCompDirectiveNoFileComp", "",
+		}, "\n")
+
+		if output != expected {
+			t.Errorf("expected: %q, got: %q", expected, output)
+		}
+	})
+}
+
 func TestCompletionForGroupedFlags(t *testing.T) {
 	getCmd := func() *Command {
 		rootCmd := &Command{

site/content/active_help.md

@@ -41,8 +41,8 @@ cmd := &cobra.Command{
 	RunE: func(cmd *cobra.Command, args []string) error {
 		return addRepo(args)
 	},
-	ValidArgsFunction: func(cmd *cobra.Command, args []string, toComplete string) ([]string, cobra.ShellCompDirective) {
-		var comps []string
+	ValidArgsFunction: func(cmd *cobra.Command, args []string, toComplete string) ([]cobra.Completion, cobra.ShellCompDirective) {
+		var comps []cobra.Completion
 		if len(args) == 0 {
 			comps = cobra.AppendActiveHelp(comps, "You must choose a name for the repo you are adding")
 		} else if len(args) == 1 {
@@ -75,7 +75,7 @@ This command does not take any more arguments
 Providing Active Help for flags is done in the same fashion as for nouns, but using the completion function registered for the flag.  For example:
 
 ```go
-_ = cmd.RegisterFlagCompletionFunc("version", func(cmd *cobra.Command, args []string, toComplete string) ([]string, cobra.ShellCompDirective) {
+_ = cmd.RegisterFlagCompletionFunc("version", func(cmd *cobra.Command, args []string, toComplete string) ([]cobra.Completion, cobra.ShellCompDirective) {
 		if len(args) != 2 {
 			return cobra.AppendActiveHelp(nil, "You must first specify the chart to install before the --version flag can be completed"), cobra.ShellCompDirectiveNoFileComp
 		}
@@ -112,10 +112,10 @@ should or should not be added (instead of reading the environment variable direc
 For example:
 
 ```go
-ValidArgsFunction: func(cmd *cobra.Command, args []string, toComplete string) ([]string, cobra.ShellCompDirective) {
+ValidArgsFunction: func(cmd *cobra.Command, args []string, toComplete string) ([]cobra.Completion, cobra.ShellCompDirective) {
 	activeHelpLevel := cobra.GetActiveHelpConfig(cmd)
 
-	var comps []string
+	var comps []cobra.Completion
 	if len(args) == 0 {
 		if activeHelpLevel != "off"  {
 			comps = cobra.AppendActiveHelp(comps, "You must choose a name for the repo you are adding")

site/content/completions/_index.md

@@ -177,7 +177,7 @@ cmd := &cobra.Command{
 	RunE: func(cmd *cobra.Command, args []string) {
 		RunGet(args[0])
 	},
-	ValidArgsFunction: func(cmd *cobra.Command, args []string, toComplete string) ([]string, cobra.ShellCompDirective) {
+	ValidArgsFunction: func(cmd *cobra.Command, args []string, toComplete string) ([]cobra.Completion, cobra.ShellCompDirective) {
 		if len(args) != 0 {
 			return nil, cobra.ShellCompDirectiveNoFileComp
 		}
@@ -211,21 +211,21 @@ ShellCompDirectiveNoFileComp
 
 // Indicates that the returned completions should be used as file extension filters.
 // For example, to complete only files of the form *.json or *.yaml:
-//    return []string{"yaml", "json"}, ShellCompDirectiveFilterFileExt
+//    return []cobra.Completion{"yaml", "json"}, cobra.ShellCompDirectiveFilterFileExt
 // For flags, using MarkFlagFilename() and MarkPersistentFlagFilename()
 // is a shortcut to using this directive explicitly.
 //
 ShellCompDirectiveFilterFileExt
 
 // Indicates that only directory names should be provided in file completion.
 // For example:
-//    return nil, ShellCompDirectiveFilterDirs
+//    return nil, cobra.ShellCompDirectiveFilterDirs
 // For flags, using MarkFlagDirname() is a shortcut to using this directive explicitly.
 //
 // To request directory names within another directory, the returned completions
 // should specify a single directory name within which to search. For example,
 // to complete directories within "themes/":
-//    return []string{"themes"}, ShellCompDirectiveFilterDirs
+//    return []cobra.Completion{"themes"}, cobra.ShellCompDirectiveFilterDirs
 //
 ShellCompDirectiveFilterDirs
 
@@ -293,8 +293,8 @@ As for nouns, Cobra provides a way of defining dynamic completion of flags.  To
 
 ```go
 flagName := "output"
-cmd.RegisterFlagCompletionFunc(flagName, func(cmd *cobra.Command, args []string, toComplete string) ([]string, cobra.ShellCompDirective) {
-	return []string{"json", "table", "yaml"}, cobra.ShellCompDirectiveDefault
+cmd.RegisterFlagCompletionFunc(flagName, func(cmd *cobra.Command, args []string, toComplete string) ([]cobra.Completion, cobra.ShellCompDirective) {
+	return []cobra.Completion{"json", "table", "yaml"}, cobra.ShellCompDirectiveDefault
 })
 ```
 Notice that calling `RegisterFlagCompletionFunc()` is done through the `command` with which the flag is associated.  In our example this dynamic completion will give results like so:
@@ -327,8 +327,8 @@ cmd.MarkFlagFilename(flagName, "yaml", "json")
 or
 ```go
 flagName := "output"
-cmd.RegisterFlagCompletionFunc(flagName, func(cmd *cobra.Command, args []string, toComplete string) ([]string, cobra.ShellCompDirective) {
-	return []string{"yaml", "json"}, ShellCompDirectiveFilterFileExt})
+cmd.RegisterFlagCompletionFunc(flagName, func(cmd *cobra.Command, args []string, toComplete string) ([]cobra.Completion, cobra.ShellCompDirective) {
+	return []cobra.Completion{"yaml", "json"}, cobra.ShellCompDirectiveFilterFileExt})
 ```
 
 ### Limit flag completions to directory names
@@ -341,15 +341,15 @@ cmd.MarkFlagDirname(flagName)
 or
 ```go
 flagName := "output"
-cmd.RegisterFlagCompletionFunc(flagName, func(cmd *cobra.Command, args []string, toComplete string) ([]string, cobra.ShellCompDirective) {
+cmd.RegisterFlagCompletionFunc(flagName, func(cmd *cobra.Command, args []string, toComplete string) ([]cobra.Completion, cobra.ShellCompDirective) {
 	return nil, cobra.ShellCompDirectiveFilterDirs
 })
 ```
 To limit completions of flag values to directory names *within another directory* you can use a combination of `RegisterFlagCompletionFunc()` and `ShellCompDirectiveFilterDirs` like so:
 ```go
 flagName := "output"
-cmd.RegisterFlagCompletionFunc(flagName, func(cmd *cobra.Command, args []string, toComplete string) ([]string, cobra.ShellCompDirective) {
-	return []string{"themes"}, cobra.ShellCompDirectiveFilterDirs
+cmd.RegisterFlagCompletionFunc(flagName, func(cmd *cobra.Command, args []string, toComplete string) ([]cobra.Completion, cobra.ShellCompDirective) {
+	return []cobra.Completion{"themes"}, cobra.ShellCompDirectiveFilterDirs
 })
 ```
 ### Descriptions for completions
@@ -370,15 +370,21 @@ $ helm s[tab]
 search  (search for a keyword in charts)  show  (show information of a chart)  status  (displays the status of the named release)
 ```
 
-Cobra allows you to add descriptions to your own completions.  Simply add the description text after each completion, following a `\t` separator.  This technique applies to completions returned by `ValidArgs`, `ValidArgsFunction` and `RegisterFlagCompletionFunc()`.  For example:
+Cobra allows you to add descriptions to your own completions.  Simply add the description text after each completion, following a `\t` separator. Cobra provides the helper function `CompletionWithDesc(string, string)` to create a completion with a description. This technique applies to completions returned by `ValidArgs`, `ValidArgsFunction` and `RegisterFlagCompletionFunc()`.  For example:
 ```go
-ValidArgsFunction: func(cmd *cobra.Command, args []string, toComplete string) ([]string, cobra.ShellCompDirective) {
-	return []string{"harbor\tAn image registry", "thanos\tLong-term metrics"}, cobra.ShellCompDirectiveNoFileComp
+ValidArgsFunction: func(cmd *cobra.Command, args []string, toComplete string) ([]cobra.Completion, cobra.ShellCompDirective) {
+	return []cobra.Completion{
+		cobra.CompletionWithDesc("harbor", "An image registry"),
+		cobra.CompletionWithDesc("thanos", "Long-term metrics")
+		}, cobra.ShellCompDirectiveNoFileComp
 }}
 ```
 or
 ```go
-ValidArgs: []string{"bash\tCompletions for bash", "zsh\tCompletions for zsh"}
+ValidArgs: []cobra.Completion{
+	cobra.CompletionWithDesc("bash", "Completions for bash"),
+	cobra.CompletionWithDesc("zsh", "Completions for zsh")
+	}
 ```
 
 If you don't want to show descriptions in the completions, you can add `--no-descriptions` to the default `completion` command to disable them, like: