Move command/flag accumulation into ParseTrace.

context.go

@@ -9,20 +9,22 @@ import (
 // ParseTrace records the nodes and parsed values from the current command-line.
 type ParseTrace struct {
 	// One of these will be non-nil.
+	App        *Application
 	Positional *Value
 	Flag       *Flag
 	Argument   *Argument
 	Command    *Command
 
+	// Flags added by this node.
+	Flags []*Flag
+
 	// Parsed value for non-commands.
 	Value reflect.Value
 }
 
 type ParseContext struct {
-	Trace   []*ParseTrace // A trace through parsed nodes.
-	Error   error         // Error that occurred during trace, if any.
-	Flags   []*Flag       // Accumulated available flags.
-	Command []string      // Full command path.
+	Trace []*ParseTrace // A trace through parsed nodes.
+	Error error         // Error that occurred during trace, if any.
 
 	node *Node // Current node being parsed.
 
@@ -31,17 +33,48 @@ type ParseContext struct {
 	scan *Scanner
 }
 
+// Flags returns the accumulated available flags.
+func (p *ParseContext) Flags() (flags []*Flag) {
+	for _, trace := range p.Trace {
+		flags = append(flags, trace.Flags...)
+	}
+	return
+}
+
+// Command returns the full command path.
+func (p *ParseContext) Command() (command []string) {
+	for _, trace := range p.Trace {
+		switch {
+		case trace.Positional != nil:
+			command = append(command, "<"+trace.Positional.Name+">")
+		case trace.Argument != nil:
+			command = append(command, "<"+trace.Argument.Name+">")
+		case trace.Command != nil:
+			command = append(command, trace.Command.Name)
+		}
+	}
+	return
+}
+
 // Trace parses the command-line, validating and collecting matching grammar nodes.
 func Trace(args []string, app *Application) (*ParseContext, error) {
 	p := &ParseContext{
 		app:  app,
 		args: args,
 	}
+	p.Trace = append(p.Trace, &ParseTrace{
+		App:   app,
+		Flags: append([]*Flag{}, app.Flags...),
+	})
 	err := p.reset(&p.app.Node)
 	if err != nil {
 		return nil, err
 	}
 	p.Error = p.trace(&p.app.Node)
+	if err = checkMissingFlags(p.Flags()); err != nil {
+		return nil, err
+	}
+
 	return p, nil
 }
 
@@ -94,7 +127,7 @@ func (p *ParseContext) reset(node *Node) error {
 func (p *ParseContext) trace(node *Node) (err error) { // nolint: gocyclo
 	positional := 0
 	p.node = node
-	p.Flags = append(p.Flags, node.Flags...)
+	flags := append(p.Flags(), node.Flags...)
 
 	for !p.scan.Peek().IsEOL() {
 		token := p.scan.Peek()
@@ -146,14 +179,14 @@ func (p *ParseContext) trace(node *Node) (err error) { // nolint: gocyclo
 			p.scan.PushTyped(token.Value[0:1], ShortFlagToken)
 
 		case FlagToken:
-			if err := p.matchFlags(func(f *Flag) bool {
+			if err := p.matchFlags(flags, func(f *Flag) bool {
 				return f.Name == token.Value
 			}); err != nil {
 				return err
 			}
 
 		case ShortFlagToken:
-			if err := p.matchFlags(func(f *Flag) bool {
+			if err := p.matchFlags(flags, func(f *Flag) bool {
 				return string(f.Name) == token.Value
 			}); err != nil {
 				return err
@@ -170,8 +203,7 @@ func (p *ParseContext) trace(node *Node) (err error) { // nolint: gocyclo
 				if err != nil {
 					return err
 				}
-				p.Command = append(p.Command, "<"+arg.Name+">")
-				p.Trace = append(p.Trace, &ParseTrace{Positional: arg, Value: value})
+				p.Trace = append(p.Trace, &ParseTrace{Positional: arg, Value: value, Flags: node.Flags})
 				positional++
 				break
 			}
@@ -182,16 +214,21 @@ func (p *ParseContext) trace(node *Node) (err error) { // nolint: gocyclo
 				case branch.Command != nil:
 					if branch.Command.Name == token.Value {
 						p.scan.Pop()
-						p.Command = append(p.Command, branch.Command.Name)
-						p.Trace = append(p.Trace, &ParseTrace{Command: branch.Command})
+						p.Trace = append(p.Trace, &ParseTrace{
+							Command: branch.Command,
+							Flags:   node.Flags,
+						})
 						return p.trace(branch.Command)
 					}
 
 				case branch.Argument != nil:
 					arg := branch.Argument.Argument
 					if value, err := arg.Parse(p.scan); err == nil {
-						p.Command = append(p.Command, "<"+arg.Name+">")
-						p.Trace = append(p.Trace, &ParseTrace{Argument: branch.Argument, Value: value})
+						p.Trace = append(p.Trace, &ParseTrace{
+							Argument: branch.Argument,
+							Value:    value,
+							Flags:    node.Flags,
+						})
 						return p.trace(&branch.Argument.Node)
 					}
 				}
@@ -211,10 +248,6 @@ func (p *ParseContext) trace(node *Node) (err error) { // nolint: gocyclo
 		return err
 	}
 
-	if err := checkMissingFlags(node.Children, p.Flags); err != nil {
-		return err
-	}
-
 	return nil
 }
 
@@ -238,11 +271,7 @@ func (p *ParseContext) Apply() (string, error) {
 	return strings.Join(path, " "), nil
 }
 
-func checkMissingFlags(children []*Branch, flags []*Flag) error {
-	// Only check required missing fields at the last child.
-	if len(children) > 0 {
-		return nil
-	}
+func checkMissingFlags(flags []*Flag) error {
 	missing := []string{}
 	for _, flag := range flags {
 		if !flag.Required || flag.Set {
@@ -295,10 +324,10 @@ func checkMissingPositionals(positional int, values []*Value) error {
 	return fmt.Errorf("missing positional arguments %s", strings.Join(missing, " "))
 }
 
-func (p *ParseContext) matchFlags(matcher func(f *Flag) bool) (err error) {
-	token := p.scan.Peek()
+func (p *ParseContext) matchFlags(flags []*Flag, matcher func(f *Flag) bool) (err error) {
 	defer catch(&err)
-	for _, flag := range p.Flags {
+	token := p.scan.Peek()
+	for _, flag := range flags {
 		// Found a matching flag.
 		if flag.Name == token.Value {
 			p.scan.Pop()