Cobra 命令自动补全指北

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$ cobra add completion

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var completionCmd = &cobra.Command{
    Use:                   "completion [bash|zsh|fish|powershell]",
    Short:                 "Generate completion script",
    Long: `To load completions:

Bash:

$ source <(yourprogram completion bash)

# To load completions for each session, execute once:
Linux:
  $ yourprogram completion bash > /etc/bash_completion.d/yourprogram
MacOS:
  $ yourprogram completion bash > /usr/local/etc/bash_completion.d/yourprogram

Zsh:

# If shell completion is not already enabled in your environment you will need
# to enable it.  You can execute the following once:

$ echo "autoload -U compinit; compinit" >> ~/.zshrc

# To load completions for each session, execute once:
$ yourprogram completion zsh > "${fpath[1]}/_yourprogram"

# You will need to start a new shell for this setup to take effect.

Fish:

$ yourprogram completion fish | source

# To load completions for each session, execute once:
$ yourprogram completion fish > ~/.config/fish/completions/yourprogram.fish
`,
    DisableFlagsInUseLine: true,
    ValidArgs:             []string{"bash", "zsh", "fish", "powershell"},
    Args:                  cobra.ExactValidArgs(1),
    Run: func(cmd *cobra.Command, args []string) {
      switch args[0] {
      case "bash":
        cmd.Root().GenBashCompletion(os.Stdout)
      case "zsh":
        cmd.Root().GenZshCompletion(os.Stdout)
      case "fish":
        cmd.Root().GenFishCompletion(os.Stdout, true)
      case "powershell":
        cmd.Root().GenPowerShellCompletion(os.Stdout)
      }
    },
}

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validArgs []string = { "pod", "node", "service", "replicationcontroller" }

cmd := &cobra.Command{
    Use:     "get [(-o|--output=)json|yaml|template|...] (RESOURCE [NAME] | RESOURCE/NAME ...)",
    Short:   "Display one or many resources",
    Long:    get_long,
    Example: get_example,
    Run: func(cmd *cobra.Command, args []string) {
      err := RunGet(f, out, cmd, args)
      util.CheckErr(err)
    },
    ValidArgs: validArgs,
}

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$ kubectl get [tab][tab]
node   pod   replicationcontroller   service

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argAliases []string = { "pods", "nodes", "services", "svc", "replicationcontrollers", "rc" }

cmd := &cobra.Command{
    ...
    ValidArgs:  validArgs,
    ArgAliases: argAliases
}

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$ kubectl get rc [tab][tab]
backend        frontend       database

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cmd := &cobra.Command{
    Use:   "status RELEASE_NAME",
    Short: "Display the status of the named release",
    Long:  status_long,
    RunE: func(cmd *cobra.Command, args []string) {
      RunGet(args[0])
    },
    ValidArgsFunction: func(cmd *cobra.Command, args []string, toComplete string) ([]string, cobra.ShellCompDirective) {
      if len(args) != 0 {
        return nil, cobra.ShellCompDirectiveNoFileComp
      }
      return getReleasesFromCluster(toComplete), cobra.ShellCompDirectiveNoFileComp
    },
}

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$ helm status [tab][tab]
harbor notary rook thanos

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// Indicates that the shell will perform its default behavior after completions
// have been provided (this implies none of the other directives).
ShellCompDirectiveDefault

// Indicates an error occurred and completions should be ignored.
ShellCompDirectiveError

// Indicates that the shell should not add a space after the completion,
// even if there is a single completion provided.
ShellCompDirectiveNoSpace

// Indicates that the shell should not provide file completion even when
// no completion is provided.
ShellCompDirectiveNoFileComp

// Indicates that the returned completions should be used as file extension filters.
// For example, to complete only files of the form *.json or *.yaml:
//    return []string{"yaml", "json"}, ShellCompDirectiveFilterFileExt
// For flags, using MarkFlagFilename() and MarkPersistentFlagFilename()
// is a shortcut to using this directive explicitly.
//
ShellCompDirectiveFilterFileExt

// Indicates that only directory names should be provided in file completion.
// For example:
//    return nil, ShellCompDirectiveFilterDirs
// For flags, using MarkFlagDirname() is a shortcut to using this directive explicitly.
//
// To request directory names within another directory, the returned completions
// should specify a single directory name within which to search. For example,
// to complete directories within "themes/":
//    return []string{"themes"}, ShellCompDirectiveFilterDirs
//
ShellCompDirectiveFilterDirs

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cmd.MarkFlagRequired("pod")
cmd.MarkFlagRequired("container")

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$ kubectl exec [tab][tab]
-c            --container=  -p            --pod=  

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flagName := "output"
cmd.RegisterFlagCompletionFunc(flagName, func(cmd *cobra.Command, args []string, toComplete string) ([]string, cobra.ShellCompDirective) {
    return []string{"json", "table", "yaml"}, cobra.ShellCompDirectiveDefault
})

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$ helm status --output [tab][tab]
json table yaml

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$ helm __complete status har[ENTER]
harbor
:4
Completion ended with directive: ShellCompDirectiveNoFileComp # This is on stderr

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$ helm __complete status ""[ENTER]
harbor
notary
rook
thanos
:4
Completion ended with directive: ShellCompDirectiveNoFileComp # This is on stderr

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$ helm __complete status --output ""[ENTER]
json
table
yaml
:4
Completion ended with directive: ShellCompDirectiveNoFileComp # This is on stderr