Repository: spf13/cobra (go)

Issue:
reusing flags for subcommand.
same Flags should be allowed to be reuse in sub-commands.

Problem:
- few flags like `-f` are synonymous to `--force` or `--file` flags. 
- Since usage of same flag is not allowed in one command tree (command, sub-commands), changing UX is required, which is not good as per UX design.


Pull request description:
Add a TraverseChildren option to allow for flags on each command in the hierarchy
Fixes #277

Currently cobra only parses flags on the last command in the chain. If you use `PersistentFlags()` you force the parent flag onto the child commands, cluttering help, and reducing the short flags available to child commands.

`TraverseChildren` allows each command in the hierarchy to have its own flags. Flags are parsed as commands are found during the `Traversal()`.


Patch:
diff --git a/README.md b/README.md
index e1b83a2..373a056 100644
--- a/README.md
+++ b/README.md
@@ -343,6 +343,19 @@ A flag can also be assigned locally which will only apply to that specific comma
 RootCmd.Flags().StringVarP(&Source, "source", "s", "", "Source directory to read from")
 ```
 
+### Local Flag on Parent Commands
+
+By default Cobra only parses local flags on the target command, any local flags on 
+parent commands are ignored. By enabling `Command.TraverseChildren` Cobra will 
+parse local flags on each command before executing the target command.
+
+```go
+command := cobra.Command{
+  Use: "print [OPTIONS] [COMMANDS]",
+  TraverseChildren: true,
+}
+```
+
 ### Bind Flags with Config
 
 You can also bind your flags with [viper](https://github.com/spf13/viper):
diff --git a/command.go b/command.go
index a0a633d..a23bb6d 100644
--- a/command.go
+++ b/command.go
@@ -125,6 +125,9 @@ type Command struct {
 	// Must be > 0.
 	SuggestionsMinimumDistance int
 
+	// TraverseChildren parses flags on all parents before executing child command.
+	TraverseChildren bool
+
 	// name is the command name, usually the executable's name.
 	name string
 	// commands is the list of commands supported by this program.
@@ -475,13 +478,14 @@ func argsMinusFirstX(args []string, x string) []string {
 	return args
 }
 
+func isFlagArg(arg string) bool {
+	return ((len(arg) >= 3 && arg[1] == '-') ||
+		(len(arg) >= 2 && arg[0] == '-' && arg[1] != '-'))
+}
+
 // Find the target command given the args and command tree
 // Meant to be run on the highest node. Only searches down.
 func (c *Command) Find(args []string) (*Command, []string, error) {
-	if c == nil {
-		return nil, nil, fmt.Errorf("Called find() on a nil Command")
-	}
-
 	var innerfind func(*Command, []string) (*Command, []string)
 
 	innerfind = func(c *Command, innerArgs []string) (*Command, []string) {
@@ -490,28 +494,11 @@ func (c *Command) Find(args []string) (*Command, []string, error) {
 			return c, innerArgs
 		}
 		nextSubCmd := argsWOflags[0]
-		matches := make([]*Command, 0)
-		for _, cmd := range c.commands {
-			if cmd.Name() == nextSubCmd || cmd.HasAlias(nextSubCmd) { // exact name or alias match
-				return innerfind(cmd, argsMinusFirstX(innerArgs, nextSubCmd))
-			}
-			if EnablePrefixMatching {
-				if strings.HasPrefix(cmd.Name(), nextSubCmd) { // prefix match
-					matches = append(matches, cmd)
-				}
-				for _, x := range cmd.Aliases {
-					if strings.HasPrefix(x, nextSubCmd) {
-						matches = append(matches, cmd)
-					}
-				}
-			}
-		}
 
-		// only accept a single prefix match - multiple matches would be ambiguous
-		if len(matches) == 1 {
-			return innerfind(matches[0], argsMinusFirstX(innerArgs, argsWOflags[0]))
+		cmd := c.findNext(nextSubCmd)
+		if cmd != nil {
+			return innerfind(cmd, argsMinusFirstX(innerArgs, nextSubCmd))
 		}
-
 		return c, innerArgs
 	}
 
@@ -539,6 +526,66 @@ func (c *Command) findSuggestions(arg string) string {
 	return suggestionsString
 }
 
+func (c *Command) findNext(next string) *Command {
+	matches := make([]*Command, 0)
+	for _, cmd := range c.commands {
+		if cmd.Name() == next || cmd.HasAlias(next) {
+			return cmd
+		}
+		if EnablePrefixMatching && cmd.hasNameOrAliasPrefix(next) {
+			matches = append(matches, cmd)
+		}
+	}
+
+	if len(matches) == 1 {
+		return matches[0]
+	}
+	return nil
+}
+
+// Traverse the command tree to find the command, and parse args for
+// each parent.
+func (c *Command) Traverse(args []string) (*Command, []string, error) {
+	flags := []string{}
+	inFlag := false
+
+	for i, arg := range args {
+		switch {
+		// A long flag with a space separated value
+		case strings.HasPrefix(arg, "--") && !strings.Contains(arg, "="):
+			// TODO: this isn't quite right, we should really check ahead for 'true' or 'false'
+			inFlag = !hasNoOptDefVal(arg[2:], c.Flags())
+			flags = append(flags, arg)
+			continue
+		// A short flag with a space separated value
+		case strings.HasPrefix(arg, "-") && !strings.Contains(arg, "=") && len(arg) == 2 && !shortHasNoOptDefVal(arg[1:], c.Flags()):
+			inFlag = true
+			flags = append(flags, arg)
+			continue
+		// The value for a flag
+		case inFlag:
+			inFlag = false
+			flags = append(flags, arg)
+			continue
+		// A flag without a value, or with an `=` separated value
+		case isFlagArg(arg):
+			flags = append(flags, arg)
+			continue
+		}
+
+		cmd := c.findNext(arg)
+		if cmd == nil {
+			return c, args, nil
+		}
+
+		if err := c.ParseFlags(flags); err != nil {
+			return nil, args, err
+		}
+		return cmd.Traverse(args[i+1:])
+	}
+	return c, args, nil
+}
+
 // SuggestionsFor provides suggestions for the typedName.
 func (c *Command) SuggestionsFor(typedName string) []string {
 	suggestions := []string{}
@@ -714,7 +761,12 @@ func (c *Command) ExecuteC() (cmd *Command, err error) {
 		args = c.args
 	}
 
-	cmd, flags, err := c.Find(args)
+	var flags []string
+	if c.TraverseChildren {
+		cmd, flags, err = c.Traverse(args)
+	} else {
+		cmd, flags, err = c.Find(args)
+	}
 	if err != nil {
 		// If found parse to a subcommand and then failed, talk about the subcommand
 		if cmd != nil {
@@ -726,6 +778,7 @@ func (c *Command) ExecuteC() (cmd *Command, err error) {
 		}
 		return c, err
 	}
+
 	err = cmd.execute(flags)
 	if err != nil {
 		// Always show help if requested, even if SilenceErrors is in
@@ -993,7 +1046,21 @@ func (c *Command) HasAlias(s string) bool {
 	return false
 }
 
-// NameAndAliases returns string containing name and all aliases
+// hasNameOrAliasPrefix returns true if the Name or any of aliases start
+// with prefix
+func (c *Command) hasNameOrAliasPrefix(prefix string) bool {
+	if strings.HasPrefix(c.Name(), prefix) {
+		return true
+	}
+	for _, alias := range c.Aliases {
+		if strings.HasPrefix(alias, prefix) {
+			return true
+		}
+	}
+	return false
+}
+
+// NameAndAliases returns a list of the command name and all aliases
 func (c *Command) NameAndAliases() string {
 	return strings.Join(append([]string{c.Name()}, c.Aliases...), ", ")
 }


Test patch:
diff --git a/command_test.go b/command_test.go
index aa6658f..938a741 100644
--- a/command_test.go
+++ b/command_test.go
@@ -347,3 +347,94 @@ func TestSetHelpCommand(t *testing.T) {
 		t.Errorf("Expected to contain %q message, but got %q", correctMessage, output.String())
 	}
 }
+
+func TestTraverseWithParentFlags(t *testing.T) {
+	cmd := &Command{
+		Use:              "do",
+		TraverseChildren: true,
+	}
+	cmd.Flags().String("foo", "", "foo things")
+	cmd.Flags().BoolP("goo", "g", false, "foo things")
+
+	sub := &Command{Use: "next"}
+	sub.Flags().String("add", "", "add things")
+	cmd.AddCommand(sub)
+
+	c, args, err := cmd.Traverse([]string{"-g", "--foo", "ok", "next", "--add"})
+	if err != nil {
+		t.Fatalf("Expected no error: %s", err)
+	}
+	if len(args) != 1 && args[0] != "--add" {
+		t.Fatalf("wrong args %s", args)
+	}
+	if c.Name() != sub.Name() {
+		t.Fatalf("wrong command %q expected %q", c.Name(), sub.Name())
+	}
+}
+
+func TestTraverseNoParentFlags(t *testing.T) {
+	cmd := &Command{
+		Use:              "do",
+		TraverseChildren: true,
+	}
+	cmd.Flags().String("foo", "", "foo things")
+
+	sub := &Command{Use: "next"}
+	sub.Flags().String("add", "", "add things")
+	cmd.AddCommand(sub)
+
+	c, args, err := cmd.Traverse([]string{"next"})
+	if err != nil {
+		t.Fatalf("Expected no error: %s", err)
+	}
+	if len(args) != 0 {
+		t.Fatalf("wrong args %s", args)
+	}
+	if c.Name() != sub.Name() {
+		t.Fatalf("wrong command %q expected %q", c.Name(), sub.Name())
+	}
+}
+
+func TestTraverseWithBadParentFlags(t *testing.T) {
+	cmd := &Command{
+		Use:              "do",
+		TraverseChildren: true,
+	}
+	sub := &Command{Use: "next"}
+	sub.Flags().String("add", "", "add things")
+	cmd.AddCommand(sub)
+
+	expected := "got unknown flag: --add"
+
+	c, _, err := cmd.Traverse([]string{"--add", "ok", "next"})
+	if err == nil || strings.Contains(err.Error(), expected) {
+		t.Fatalf("Expected error %s got %s", expected, err)
+	}
+	if c != nil {
+		t.Fatalf("Expected nil command")
+	}
+}
+
+func TestTraverseWithBadChildFlag(t *testing.T) {
+	cmd := &Command{
+		Use:              "do",
+		TraverseChildren: true,
+	}
+	cmd.Flags().String("foo", "", "foo things")
+
+	sub := &Command{Use: "next"}
+	cmd.AddCommand(sub)
+
+	// Expect no error because the last commands args shouldn't be parsed in
+	// Traverse
+	c, args, err := cmd.Traverse([]string{"next", "--add"})
+	if err != nil {
+		t.Fatalf("Expected no error: %s", err)
+	}
+	if len(args) != 1 && args[0] != "--add" {
+		t.Fatalf("wrong args %s", args)
+	}
+	if c.Name() != sub.Name() {
+		t.Fatalf("wrong command %q expected %q", c.Name(), sub.Name())
+	}
+}