Add support for flags bash completion

app_test.go

@@ -221,6 +221,89 @@ func ExampleApp_Run_subcommandNoAction() {
 
 }
 
+func ExampleApp_Run_bashComplete_withShortFlag() {
+	os.Args = []string{"greet", "-", "--generate-bash-completion"}
+
+	app := NewApp()
+	app.Name = "greet"
+	app.EnableBashCompletion = true
+	app.Flags = []Flag{
+		IntFlag{
+			Name: "other,o",
+		},
+		StringFlag{
+			Name: "xyz,x",
+		},
+	}
+
+	app.Run(os.Args)
+	// Output:
+	// --other
+	// -o
+	// --xyz
+	// -x
+	// --help
+	// -h
+	// --version
+	// -v
+}
+
+func ExampleApp_Run_bashComplete_withLongFlag() {
+	os.Args = []string{"greet", "--s", "--generate-bash-completion"}
+
+	app := NewApp()
+	app.Name = "greet"
+	app.EnableBashCompletion = true
+	app.Flags = []Flag{
+		IntFlag{
+			Name: "other,o",
+		},
+		StringFlag{
+			Name: "xyz,x",
+		},
+		StringFlag{
+			Name: "some-flag,s",
+		},
+		StringFlag{
+			Name: "similar-flag",
+		},
+	}
+
+	app.Run(os.Args)
+	// Output:
+	// --some-flag
+	// --similar-flag
+}
+func ExampleApp_Run_bashComplete_withMultipleLongFlag() {
+	os.Args = []string{"greet", "--st", "--generate-bash-completion"}
+
+	app := NewApp()
+	app.Name = "greet"
+	app.EnableBashCompletion = true
+	app.Flags = []Flag{
+		IntFlag{
+			Name: "int-flag,i",
+		},
+		StringFlag{
+			Name: "string,s",
+		},
+		StringFlag{
+			Name: "string-flag-2",
+		},
+		StringFlag{
+			Name: "similar-flag",
+		},
+		StringFlag{
+			Name: "some-flag",
+		},
+	}
+
+	app.Run(os.Args)
+	// Output:
+	// --string
+	// --string-flag-2
+}
+
 func ExampleApp_Run_bashComplete() {
 	// set args for examples sake
 	os.Args = []string{"greet", "--generate-bash-completion"}

autocomplete/bash_autocomplete

@@ -3,14 +3,19 @@
 : ${PROG:=$(basename ${BASH_SOURCE})}
 
 _cli_bash_autocomplete() {
+  if [[ "${COMP_WORDS[0]}" != "source" ]]; then
     local cur opts base
     COMPREPLY=()
     cur="${COMP_WORDS[COMP_CWORD]}"
-    opts=$( ${COMP_WORDS[@]:0:$COMP_CWORD} --generate-bash-completion )
+    if [[ "$cur" == "-"* ]]; then
+      opts=$( ${COMP_WORDS[@]:0:$COMP_CWORD} ${cur} --generate-bash-completion )
+    else
+      opts=$( ${COMP_WORDS[@]:0:$COMP_CWORD} --generate-bash-completion )
+    fi
     COMPREPLY=( $(compgen -W "${opts}" -- ${cur}) )
     return 0
+  fi
 }
 
-complete -F _cli_bash_autocomplete $PROG
-
+complete -o bashdefault -o default -o nospace -F _cli_bash_autocomplete $PROG
 unset PROG

help.go

@@ -7,6 +7,7 @@ import (
 	"strings"
 	"text/tabwriter"
 	"text/template"
+	"unicode/utf8"
 )
 
 // AppHelpTemplate is the text template for the Default help topic.
@@ -157,19 +158,88 @@ func ShowAppHelp(c *Context) (err error) {
 
 // DefaultAppComplete prints the list of subcommands as the default app completion method
 func DefaultAppComplete(c *Context) {
-	for _, command := range c.App.Commands {
+	DefaultCompleteWithFlags(nil)(c)
+}
+
+func printCommandSuggestions(commands []Command, writer io.Writer) {
+	for _, command := range commands {
 		if command.Hidden {
 			continue
 		}
 		if os.Getenv("_CLI_ZSH_AUTOCOMPLETE_HACK") == "1" {
 			for _, name := range command.Names() {
-				fmt.Fprintf(c.App.Writer, "%s:%s\n", name, command.Usage)
+				fmt.Fprintf(writer, "%s:%s\n", name, command.Usage)
 			}
 		} else {
 			for _, name := range command.Names() {
-				fmt.Fprintf(c.App.Writer, "%s\n", name)
+				fmt.Fprintf(writer, "%s\n", name)
+			}
+		}
+	}
+}
+
+func cliArgContains(flagName string) bool {
+	for _, name := range strings.Split(flagName, ",") {
+		name = strings.TrimSpace(name)
+		count := utf8.RuneCountInString(name)
+		if count > 2 {
+			count = 2
+		}
+		flag := fmt.Sprintf("%s%s", strings.Repeat("-", count), name)
+		for _, a := range os.Args {
+			if a == flag {
+				return true
+			}
+		}
+	}
+	return false
+}
+
+func printFlagSuggestions(lastArg string, flags []Flag, writer io.Writer) {
+	cur := strings.TrimPrefix(lastArg, "-")
+	cur = strings.TrimPrefix(cur, "-")
+	for _, flag := range flags {
+		if bflag, ok := flag.(BoolFlag); ok && bflag.Hidden {
+			continue
+		}
+		for _, name := range strings.Split(flag.GetName(), ",") {
+			name = strings.TrimSpace(name)
+			// this will get total count utf8 letters in flag name
+			count := utf8.RuneCountInString(name)
+			if count > 2 {
+				count = 2 // resuse this count to generate single - or -- in flag completion
+			}
+			// if flag name has more than one utf8 letter and last argument in cli has -- prefix then
+			// skip flag completion for short flags example -v or -x
+			if strings.HasPrefix(lastArg, "--") && count == 1 {
+				continue
+			}
+			// match if last argument matches this flag and it is not repeated
+			if strings.HasPrefix(name, cur) && cur != name && !cliArgContains(flag.GetName()) {
+				flagCompletion := fmt.Sprintf("%s%s", strings.Repeat("-", count), name)
+				fmt.Fprintln(writer, flagCompletion)
+			}
+		}
+	}
+}
+
+func DefaultCompleteWithFlags(cmd *Command) func(c *Context) {
+	return func(c *Context) {
+		if len(os.Args) > 2 {
+			lastArg := os.Args[len(os.Args)-2]
+			if strings.HasPrefix(lastArg, "-") {
+				printFlagSuggestions(lastArg, c.App.Flags, c.App.Writer)
+				if cmd != nil {
+					printFlagSuggestions(lastArg, cmd.Flags, c.App.Writer)
+				}
+				return
 			}
 		}
+		if cmd != nil {
+			printCommandSuggestions(cmd.Subcommands, c.App.Writer)
+		} else {
+			printCommandSuggestions(c.App.Commands, c.App.Writer)
+		}
 	}
 }
 
@@ -231,9 +301,14 @@ func ShowCompletions(c *Context) {
 // ShowCommandCompletions prints the custom completions for a given command
 func ShowCommandCompletions(ctx *Context, command string) {
 	c := ctx.App.Command(command)
-	if c != nil && c.BashComplete != nil {
-		c.BashComplete(ctx)
+	if c != nil {
+		if c.BashComplete != nil {
+			c.BashComplete(ctx)
+		} else {
+			DefaultCompleteWithFlags(c)(ctx)
+		}
 	}
+
 }
 
 func printHelpCustom(out io.Writer, templ string, data interface{}, customFunc map[string]interface{}) {