Extra output and errors during shell completion

[marckhouzam]

What steps did you take: There is extra output in the shell completion choices and in some cases is even causes errors during shell completion. Same issue in kapp: https://github.com/vmware-tanzu/carvel-kapp/issues/583

What happened:

For bash, notice the error in this particular case (some other bash completions do work):

bash
bash-5.1$ source <(imgpkg completion bash)
bash-5.1$ imgpkg help <TAB>
bash: ShellCompDirectiveNoFileComp

Succeeded: syntax error in expression (error token is "Succeeded")

For zsh, notice the extra output at the end (:4, Succeeded, etc):

$ source <(imgpkg completion zsh)
$ compdef _imgpkg imgpkg
$ imgpkg <TAB>
completion                                                     -- Generate completion script
copy                                                           -- Copy a bundle from one location to another
describe                                                       -- Describe the images and bundles associated with a give bundle
help                                                           -- Help about any command
pull                                                           -- Pull files from bundle, image, or bundle lock file
push                                                           -- Push files as image
tag                                                            -- Tag (list, resolve)
version                                                        -- Print client version
:4                                                             Succeeded
Completion ended with directive: ShellCompDirectiveNoFileComp

Also happens for fish shell.

What did you expect:

Shell completion to work as expected, without error or extra output.

Anything else you would like to add:

Shell completion uses the hidden __complete command provided by the Cobra project to obtain the shell completion choices.

1. imgpkg should not print Succeeded for that command
2. output printed to stderr by the __complete command should not be redirected by imgpkg to stdout (that is the problem for the string output Completion ended with directive: ShellCompDirectiveNoFileComp)

This command is added by Cobra when rootCmd.Execute() is called, which makes it a little trickier to adjust the behaviour for it.

Environment:

• imgpkg version (use imgpkg --version): 0.30.0
• Docker registry used (e.g. Docker HUB): N/A
• OS (e.g. from /etc/os-release): MacOS

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[joaopapereira]

Hey, @marckhouzam thanks for creating the issue. We will sync up with kapp folk and get this fix. Also if you are interested in getting a PR with a fix for this we will be more than happy to look at it

[aaronshurley]

Shipped as a part of v0.34.0.

[marckhouzam]

Shipped as a part of v0.34.0.

Works great! Thanks!