441 lines
11 KiB
Go
441 lines
11 KiB
Go
package cli
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import (
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"fmt"
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"io"
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"os"
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"sort"
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"strings"
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"sync"
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"text/template"
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"github.com/armon/go-radix"
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)
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// CLI contains the state necessary to run subcommands and parse the
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// command line arguments.
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//
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// CLI also supports nested subcommands, such as "cli foo bar". To use
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// nested subcommands, the key in the Commands mapping below contains the
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// full subcommand. In this example, it would be "foo bar".
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//
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// If you use a CLI with nested subcommands, some semantics change due to
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// ambiguities:
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//
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// * We use longest prefix matching to find a matching subcommand. This
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// means if you register "foo bar" and the user executes "cli foo qux",
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// the "foo" commmand will be executed with the arg "qux". It is up to
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// you to handle these args. One option is to just return the special
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// help return code `RunResultHelp` to display help and exit.
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//
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// * The help flag "-h" or "-help" will look at all args to determine
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// the help function. For example: "otto apps list -h" will show the
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// help for "apps list" but "otto apps -h" will show it for "apps".
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// In the normal CLI, only the first subcommand is used.
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//
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// * The help flag will list any subcommands that a command takes
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// as well as the command's help itself. If there are no subcommands,
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// it will note this. If the CLI itself has no subcommands, this entire
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// section is omitted.
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//
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// * Any parent commands that don't exist are automatically created as
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// no-op commands that just show help for other subcommands. For example,
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// if you only register "foo bar", then "foo" is automatically created.
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//
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type CLI struct {
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// Args is the list of command-line arguments received excluding
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// the name of the app. For example, if the command "./cli foo bar"
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// was invoked, then Args should be []string{"foo", "bar"}.
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Args []string
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// Commands is a mapping of subcommand names to a factory function
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// for creating that Command implementation. If there is a command
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// with a blank string "", then it will be used as the default command
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// if no subcommand is specified.
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//
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// If the key has a space in it, this will create a nested subcommand.
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// For example, if the key is "foo bar", then to access it our CLI
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// must be accessed with "./cli foo bar". See the docs for CLI for
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// notes on how this changes some other behavior of the CLI as well.
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Commands map[string]CommandFactory
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// Name defines the name of the CLI.
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Name string
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// Version of the CLI.
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Version string
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// HelpFunc and HelpWriter are used to output help information, if
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// requested.
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//
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// HelpFunc is the function called to generate the generic help
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// text that is shown if help must be shown for the CLI that doesn't
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// pertain to a specific command.
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//
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// HelpWriter is the Writer where the help text is outputted to. If
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// not specified, it will default to Stderr.
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HelpFunc HelpFunc
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HelpWriter io.Writer
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once sync.Once
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commandTree *radix.Tree
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commandNested bool
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isHelp bool
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subcommand string
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subcommandArgs []string
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topFlags []string
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isVersion bool
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}
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// NewClI returns a new CLI instance with sensible defaults.
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func NewCLI(app, version string) *CLI {
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return &CLI{
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Name: app,
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Version: version,
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HelpFunc: BasicHelpFunc(app),
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}
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}
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// IsHelp returns whether or not the help flag is present within the
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// arguments.
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func (c *CLI) IsHelp() bool {
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c.once.Do(c.init)
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return c.isHelp
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}
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// IsVersion returns whether or not the version flag is present within the
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// arguments.
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func (c *CLI) IsVersion() bool {
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c.once.Do(c.init)
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return c.isVersion
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}
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// Run runs the actual CLI based on the arguments given.
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func (c *CLI) Run() (int, error) {
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c.once.Do(c.init)
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// Just show the version and exit if instructed.
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if c.IsVersion() && c.Version != "" {
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c.HelpWriter.Write([]byte(c.Version + "\n"))
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return 1, nil
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}
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// Attempt to get the factory function for creating the command
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// implementation. If the command is invalid or blank, it is an error.
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raw, ok := c.commandTree.Get(c.Subcommand())
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if !ok {
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c.HelpWriter.Write([]byte(c.HelpFunc(c.helpCommands(c.subcommandParent())) + "\n"))
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return 1, nil
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}
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command, err := raw.(CommandFactory)()
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if err != nil {
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return 0, err
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}
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// If we've been instructed to just print the help, then print it
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if c.IsHelp() {
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c.commandHelp(command)
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return 1, nil
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}
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// If there is an invalid flag, then error
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if len(c.topFlags) > 0 {
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c.HelpWriter.Write([]byte(
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"Invalid flags before the subcommand. If these flags are for\n" +
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"the subcommand, please put them after the subcommand.\n\n"))
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c.commandHelp(command)
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return 1, nil
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}
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code := command.Run(c.SubcommandArgs())
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if code == RunResultHelp {
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// Requesting help
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c.commandHelp(command)
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return 1, nil
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}
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return code, nil
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}
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// Subcommand returns the subcommand that the CLI would execute. For
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// example, a CLI from "--version version --help" would return a Subcommand
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// of "version"
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func (c *CLI) Subcommand() string {
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c.once.Do(c.init)
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return c.subcommand
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}
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// SubcommandArgs returns the arguments that will be passed to the
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// subcommand.
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func (c *CLI) SubcommandArgs() []string {
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c.once.Do(c.init)
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return c.subcommandArgs
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}
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// subcommandParent returns the parent of this subcommand, if there is one.
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// If there isn't on, "" is returned.
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func (c *CLI) subcommandParent() string {
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// Get the subcommand, if it is "" alread just return
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sub := c.Subcommand()
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if sub == "" {
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return sub
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}
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// Clear any trailing spaces and find the last space
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sub = strings.TrimRight(sub, " ")
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idx := strings.LastIndex(sub, " ")
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if idx == -1 {
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// No space means our parent is root
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return ""
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}
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return sub[:idx]
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}
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func (c *CLI) init() {
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if c.HelpFunc == nil {
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c.HelpFunc = BasicHelpFunc("app")
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if c.Name != "" {
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c.HelpFunc = BasicHelpFunc(c.Name)
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}
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}
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if c.HelpWriter == nil {
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c.HelpWriter = os.Stderr
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}
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// Build our command tree
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c.commandTree = radix.New()
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c.commandNested = false
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for k, v := range c.Commands {
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k = strings.TrimSpace(k)
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c.commandTree.Insert(k, v)
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if strings.ContainsRune(k, ' ') {
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c.commandNested = true
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}
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}
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// Go through the key and fill in any missing parent commands
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if c.commandNested {
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var walkFn radix.WalkFn
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toInsert := make(map[string]struct{})
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walkFn = func(k string, raw interface{}) bool {
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idx := strings.LastIndex(k, " ")
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if idx == -1 {
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// If there is no space, just ignore top level commands
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return false
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}
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// Trim up to that space so we can get the expected parent
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k = k[:idx]
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if _, ok := c.commandTree.Get(k); ok {
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// Yay we have the parent!
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return false
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}
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// We're missing the parent, so let's insert this
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toInsert[k] = struct{}{}
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// Call the walk function recursively so we check this one too
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return walkFn(k, nil)
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}
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// Walk!
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c.commandTree.Walk(walkFn)
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// Insert any that we're missing
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for k, _ := range toInsert {
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var f CommandFactory = func() (Command, error) {
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return &MockCommand{
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HelpText: "This command is accessed by using one of the subcommands below.",
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RunResult: RunResultHelp,
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}, nil
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}
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c.commandTree.Insert(k, f)
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}
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}
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// Process the args
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c.processArgs()
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}
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func (c *CLI) commandHelp(command Command) {
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// Get the template to use
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tpl := strings.TrimSpace(defaultHelpTemplate)
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if t, ok := command.(CommandHelpTemplate); ok {
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tpl = t.HelpTemplate()
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}
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if !strings.HasSuffix(tpl, "\n") {
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tpl += "\n"
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}
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// Parse it
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t, err := template.New("root").Parse(tpl)
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if err != nil {
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t = template.Must(template.New("root").Parse(fmt.Sprintf(
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"Internal error! Failed to parse command help template: %s\n", err)))
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}
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// Template data
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data := map[string]interface{}{
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"Name": c.Name,
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"Help": command.Help(),
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}
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// Build subcommand list if we have it
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var subcommandsTpl []map[string]interface{}
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if c.commandNested {
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// Get the matching keys
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subcommands := c.helpCommands(c.Subcommand())
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keys := make([]string, 0, len(subcommands))
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for k, _ := range subcommands {
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keys = append(keys, k)
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}
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// Sort the keys
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sort.Strings(keys)
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// Figure out the padding length
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var longest int
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for _, k := range keys {
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if v := len(k); v > longest {
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longest = v
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}
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}
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// Go through and create their structures
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subcommandsTpl = make([]map[string]interface{}, 0, len(subcommands))
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for k, raw := range subcommands {
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// Get the command
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sub, err := raw()
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if err != nil {
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c.HelpWriter.Write([]byte(fmt.Sprintf(
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"Error instantiating %q: %s", k, err)))
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}
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// Find the last space and make sure we only include that last part
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name := k
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if idx := strings.LastIndex(k, " "); idx > -1 {
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name = name[idx+1:]
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}
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subcommandsTpl = append(subcommandsTpl, map[string]interface{}{
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"Name": name,
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"NameAligned": name + strings.Repeat(" ", longest-len(k)),
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"Help": sub.Help(),
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"Synopsis": sub.Synopsis(),
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})
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}
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}
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data["Subcommands"] = subcommandsTpl
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// Write
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err = t.Execute(c.HelpWriter, data)
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if err == nil {
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return
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}
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// An error, just output...
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c.HelpWriter.Write([]byte(fmt.Sprintf(
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"Internal error rendering help: %s", err)))
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}
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// helpCommands returns the subcommands for the HelpFunc argument.
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// This will only contain immediate subcommands.
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func (c *CLI) helpCommands(prefix string) map[string]CommandFactory {
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// If our prefix isn't empty, make sure it ends in ' '
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if prefix != "" && prefix[len(prefix)-1] != ' ' {
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prefix += " "
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}
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// Get all the subkeys of this command
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var keys []string
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c.commandTree.WalkPrefix(prefix, func(k string, raw interface{}) bool {
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// Ignore any sub-sub keys, i.e. "foo bar baz" when we want "foo bar"
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if !strings.Contains(k[len(prefix):], " ") {
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keys = append(keys, k)
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}
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return false
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})
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// For each of the keys return that in the map
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result := make(map[string]CommandFactory, len(keys))
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for _, k := range keys {
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raw, ok := c.commandTree.Get(k)
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if !ok {
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// We just got it via WalkPrefix above, so we just panic
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panic("not found: " + k)
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}
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result[k] = raw.(CommandFactory)
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}
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return result
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}
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func (c *CLI) processArgs() {
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for i, arg := range c.Args {
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if c.subcommand == "" {
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// Check for version and help flags if not in a subcommand
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if arg == "-v" || arg == "-version" || arg == "--version" {
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c.isVersion = true
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continue
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}
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if arg == "-h" || arg == "-help" || arg == "--help" {
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c.isHelp = true
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continue
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}
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if arg != "" && arg[0] == '-' {
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// Record the arg...
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c.topFlags = append(c.topFlags, arg)
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}
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}
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// If we didn't find a subcommand yet and this is the first non-flag
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// argument, then this is our subcommand. j
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if c.subcommand == "" && arg != "" && arg[0] != '-' {
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c.subcommand = arg
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if c.commandNested {
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// Nested CLI, the subcommand is actually the entire
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// arg list up to a flag that is still a valid subcommand.
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k, _, ok := c.commandTree.LongestPrefix(strings.Join(c.Args[i:], " "))
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if ok {
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c.subcommand = k
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i += strings.Count(k, " ")
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}
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}
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// The remaining args the subcommand arguments
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c.subcommandArgs = c.Args[i+1:]
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}
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}
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// If we never found a subcommand and support a default command, then
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// switch to using that.
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if c.subcommand == "" {
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if _, ok := c.Commands[""]; ok {
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args := c.topFlags
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args = append(args, c.subcommandArgs...)
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c.topFlags = nil
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c.subcommandArgs = args
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}
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}
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}
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const defaultHelpTemplate = `
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{{.Help}}{{if gt (len .Subcommands) 0}}
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Subcommands:
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{{ range $value := .Subcommands }}
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{{ $value.NameAligned }} {{ $value.Synopsis }}{{ end }}
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{{ end }}
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`
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