fixes, add optional args

Author: broothie

argument.go

@@ -9,9 +9,10 @@ import (
 )
 
 type Argument struct {
-	name        string
-	description string
-	parser      argParser
+	name         string
+	description  string
+	parser       argParser
+	defaultValue any
 
 	value any
 }
@@ -31,7 +32,19 @@ func newArgument(name, description string, options ...option.Option[*Argument])
 	return argument, nil
 }
 
+func (a *Argument) isRequired() bool {
+	return a.defaultValue == nil
+}
+
+func (a *Argument) isOptional() bool {
+	return !a.isRequired()
+}
+
 func (a *Argument) inBrackets() string {
+	if a.isOptional() {
+		return fmt.Sprintf("<%s?>", a.name)
+	}
+
 	return fmt.Sprintf("<%s>", a.name)
 }
 

argument_input_validation.go

@@ -5,7 +5,7 @@ import "github.com/bobg/errors"
 var ArgumentMissingValueError = errors.New("argument missing value")
 
 func (a *Argument) validateInput() error {
-	if a.value == nil {
+	if a.isRequired() && a.value == nil {
 		return errors.Wrapf(ArgumentMissingValueError, "argument %q", a.name)
 	}
 

argument_options.go

@@ -9,3 +9,17 @@ func SetArgParser[T any](parser ArgParser[T]) option.Func[*Argument] {
 		return argument, nil
 	}
 }
+
+// SetArgDefault sets the default value of the argument.
+func SetArgDefault[T Parseable](defaultValue T) option.Func[*Argument] {
+	return func(argument *Argument) (*Argument, error) {
+		argParser, err := argParserFromParseable[T]()
+		if err != nil {
+			return nil, err
+		}
+
+		argument.parser = argParser
+		argument.defaultValue = defaultValue
+		return argument, nil
+	}
+}

command.go

@@ -55,7 +55,7 @@ func Run(name, description string, options ...option.Option[*Command]) {
 	if err := command.Run(context.Background(), os.Args[1:]); err != nil {
 		fmt.Println(err)
 
-		if exitErr := new(exec.ExitError); errors.As(err, exitErr) {
+		if exitErr := new(exec.ExitError); errors.As(err, &exitErr) {
 			os.Exit(exitErr.ExitCode())
 		} else {
 			os.Exit(1)
@@ -65,8 +65,10 @@ func Run(name, description string, options ...option.Option[*Command]) {
 
 // Run runs the command.
 func (c *Command) Run(ctx context.Context, rawArgs []string) error {
-	if err := c.newParser(rawArgs).parse(ctx); err != nil {
+	if commandProcessed, err := c.newParser(rawArgs).parse(ctx); err != nil {
 		return err
+	} else if commandProcessed {
+		return nil
 	}
 
 	return c.runHandler(ctx)
@@ -78,7 +80,13 @@ func (c *Command) runHandler(ctx context.Context) error {
 	} else if c.isVersionFlagAsserted() {
 		fmt.Println(c.findVersion())
 		return nil
-	} else if c.handler == nil {
+	}
+
+	if err := c.validateInput(); err != nil {
+		return err
+	}
+
+	if c.handler == nil {
 		return c.renderHelp(os.Stdout)
 	}
 

command_options.go

@@ -1,6 +1,10 @@
 package cli
 
-import "github.com/broothie/option"
+import (
+	"sort"
+
+	"github.com/broothie/option"
+)
 
 const versionFlagName = "version"
 
@@ -64,6 +68,8 @@ func AddArg(name, description string, options ...option.Option[*Argument]) optio
 		}
 
 		command.arguments = append(command.arguments, argument)
+		sort.SliceStable(command.arguments, func(i, j int) bool { return command.arguments[i].isRequired() && command.arguments[j].isOptional() })
+
 		return command, nil
 	}
 }

context.go

@@ -45,7 +45,11 @@ func ArgValue[T any](ctx context.Context, name string) (T, error) {
 		return zero, errors.Wrapf(ArgumentNotFoundError, "finding argument %q", name)
 	}
 
-	return arg.value.(T), nil
+	if arg.value != nil {
+		return arg.value.(T), nil
+	}
+
+	return arg.defaultValue.(T), nil
 }
 
 var commandContextKey struct{}

flag.go

@@ -51,12 +51,14 @@ func (c *Command) findFlag(name string) (*Flag, bool) {
 
 func (c *Command) findFlagUpToRoot(predicate func(*Flag) bool) (*Flag, bool) {
 	for current := c; current != nil; current = current.parent {
+		currentIsSelf := current == c
+
 		flags := current.flags
-		if currentIsSelf := current == c; !currentIsSelf {
+		if !currentIsSelf {
 			flags = lo.Filter(flags, func(flag *Flag, _ int) bool { return flag.isInherited })
 		}
 
-		flag, found := lo.Find(c.flags, predicate)
+		flag, found := lo.Find(flags, predicate)
 		if found {
 			return flag, true
 		}

flag_options.go

@@ -1,7 +1,6 @@
 package cli
 
 import (
-	"github.com/bobg/errors"
 	"github.com/broothie/option"
 )
 
@@ -42,7 +41,7 @@ func SetFlagDefault[T Parseable](defaultValue T) option.Func[*Flag] {
 	return func(flag *Flag) (*Flag, error) {
 		argParser, err := argParserFromParseable[T]()
 		if err != nil {
-			return nil, errors.Wrapf(err, "")
+			return nil, err
 		}
 
 		flag.parser = argParser

parser.go

@@ -40,17 +40,15 @@ func (c *Command) newParser(tokens []string) *parser {
 	return newParser(c, tokens)
 }
 
-func (p *parser) parse(ctx context.Context) error {
+func (p *parser) parse(ctx context.Context) (bool, error) {
 	for p.index < len(p.tokens) {
 		commandProcessed, err := p.parseArg(ctx)
-		if err != nil {
-			return err
-		} else if commandProcessed {
-			return nil
+		if err != nil || commandProcessed {
+			return true, err
 		}
 	}
 
-	return p.command.validateInput()
+	return false, nil
 }
 
 func (p *parser) parseArg(ctx context.Context) (bool, error) {