Change:
<ins> #!/usr/bin/env bash # If we are completing a flag, use Cobra's builtin completion system. # To know if we are completing a flag we need the last argument starts with a `-` and does not contain an `=` args=("$@") lastArg=${args[((${#args[@]}-1))]} if [[ "$lastArg" == -* ]]; then if [[ "$lastArg" != *=* ]]; then kubectl ns __complete "$@" fi else # TODO Make sure we are not completing the value of a flag. # TODO Only complete a single argument. # Both are pretty hard to do in a shell script.  The better way to do this would be to let # Cobra do all the completions by using `cobra.ValidArgsFunction` in the program. # But the below, although imperfect, is a nice example for plugins that don't use Cobra. # We are probably completing an argument.  This plugin only accepts namespaces, let's fetch them. kubectl get namespaces --output go-template='{{ range .items }}{{ .metadata.name }}{{"n"}}{{ end }}' # Turn off file completion.  See the ShellCompDirective documentation within # https://github.com/spf13/cobra/blob/main/shell_completions.md#completion-of-nouns echo :4 fi </ins>

Discussion:
<!-- Please only use this template for submitting enhancement requests --What would you like to be : I type <kbdTab</kbd<kbdTab</kbdI would like to see kubectl plugins in the list of suggested subcommands. For example, if I have installed , subcommand completions should suggest . the plugin itself also supports command-line completion, <kbdTab</kbd<kbdTab</kbdshould show suggestions from the plugin command completion. Why is this needed: Plugins fill in niches in the kubectl workflow, so that they are used rather seldomly. This means that plugin users need to memorize plugin names and their options over long times without using them. Therefore, plugin usefulness would be greatly enhanced by suggesting plugin sub-commands and their options.
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In fact, already supports command completion. You can run for more information about it. If you are using bash shelljust run , and then it will work!
Hi , but I'm not talking about command completion in general. I'm talking about command completion for plugins. For example, the new plugin system allows to call a plugin at location as . It would be nice to get suggested/completed, when typing <kbdTab</kbd. Further, if plugin names are completed, so should be options for those plugins -- provided the plugin offers some form of command completion.
I try to implement completion for kubectl plugins!
Were you able to make progress on this? I have a working patch for the completion of the plugin name (part 1 of this issue). I can make a PR for it if it can help.
This is a great first step! I do think however, that the real value is auto-completion for the plugin options. I can roughly remember what plugins I have, but not what options they offer. That's the real value here, I think. This will probably need a contract for how plugins make completion available (e.g. by following the kubectl standard of ). WDYT?
I've been thinking about how to do the plugin options completion.

Based on the patch I have now, I believe what will be needed is to be able to ask the plugin what the possible completions can be (based on the user-specified parameters). So the plugin won't need to generate a bash or zsh completion script (which is difficult for the author of the plugin) but just output possible completions. This also has the benefit of being independent of which shell is used. One way is to do as you mention and have the plugin support as a way to ask the plugin what the completions would be. Although it won't behave in the same fashion as (as it won't generate a completion script, and is shell-independent), I like that option because it simply requires a plugin author to provide a different script called which the bash completion logic can call. Another way would be to ask the plugin itself to support a flag such as which would return the possible completions. I don't like this because if the plugin doesn't support this flag, we'd be calling it and who knows what it would do in that unexpected case. The use of makes it easy to check of presence or absence of completion support. So I suggest that the contract with plugins be that a plugin that supports completion would provide two scripts and that the bash completion script call to get the list of completions. Any thoughts?
Hi guys, I've already implemented completion for plugins (subcommands only, doesn't include options) as However it needs to be refactored more. You can try completion for plugins with the following steps: First, prepare the repository, and build a kubectl. Install kubectl-hello plugin for completion testing. Load the kubectl completion code. You can see completion for some plugins.
Cool! You've used the same technique I did. However, may I suggest re-using the code from the plugin package instead of copying it?
Well, you are absolutely right in saying that we can't just call a plugin with some flag to produce the completion script, because who knows what will happen. Therefore, option completion for plugins has to go the route via an external completion script, like However, I'm pretty sure that those completion files need to be bash/zsh scripts, because they need to process contextual information.

For example, say I have a plugin with sub-commands Then I want completion to work as follows: As you say, this will have to be maintained by the plugin authors. Can you take a typical cobra command completion script as basis and work out how kubectl-plugin-completion and this external script need to work together? You could even try to have kubectl as its own plugin, like and or so :grinning:
kubectl already has some dynamic completion code to allow to complete pod names for example, which actually calls kubectl itself. I think I can use the same technique for plugin parameter completion. So here's an example of what I'm thinking: Then when the user types the kubectl completion script will call . This call will return which will be given to the shell by the kubectl completion script. I haven't actually tested this example, so I could be wrong. I'll try implementing it to see if I'm missing something.
Thank you for supporting me ;) I add you as co-author to commit when I send a PR.
Thanks
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I've been working on auto-completion for the Helm project and I have a proposal with a PR that fully supports auto-completion for Helm plugins. I believe the fundamental aspects of the solution would apply just as well to kubectl. Some adaptation would be needed to adjust to how kubectl supports plugins, but I think it wouldn't be very hard.
Is there an ETA on this? If I see it correctly, this is currently preventing plugin authors to implement completions as the generated completion suggestions are based off the root command and not the subcommand aka plugin. I've been trying all day to make this work but failed and that's when I stumbled over this issue..
Several major issues I see here are: We don't want files like as proposed in previous comment. We had a requirement prior to kubectl 1.12 and it didn't look great at all. The simplicity of plugins is valuable to us. (Also, unlike Helm plugins, kubectl plugins don't live at a particular directory, or follow a directory structure.)Plugin completions most likely would be integrated into commands, which a lot of people put in their or file. We need to keep this command fast. So what if the command called a special command on each plugin, in parallel, to inquire if it has completion available (e.g.), with a short deadline, and cached the successful results (maybe keyed with on plugin binary’s stat data, or checksum). That way, cmd could also provide data about plugins, while periodically refreshing the cached completion scripts.
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any updates on this one ? is it complete/done?
No update, still open..
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Sorry to revive this thread a bit but while working on another cli using the same cobra completion system by (implemented by i believe) I found out that it would not be too hard or too disruptive to have a small patch on the shell completion directly. For example with kubectl if we have a patch like this (using zsh but I am guessing the same technique will apply for bash or others) : the patch will check the first command () and the second command for example "krew" exist as and then use it directly for completion otherwise do the normal completion 'thingy'. the only downside is that the initial plugin would not show i.e: if you do you won't get krew as the plugin name, except if we add all plugin to the Root Command like the pull request from does. I don't think it would be too intensive since it is a zsh/bash builtin and in memory. I have made a small asciinema to demonstrate how it works I guess if we want this we may need to do it directly in cobra, do you think a patch like this could get accepted ?

(I had somehow difficulties to get PR reviewer and merged in cobra last time I tried)
Thanks for the suggestion. The idea is good but doesn't generalize perfectly. The command is available for programs that use Cobra but kubectl plugins can be something else (a script, a Python program, a Go program that doesn't use Cobra, etc). So we couldn't do something like this, unless we required every plugin to provide a command. I'm working on porting Helm's plugin completion solution to kubectl and should have something for the community to try soon. Plugins using Cobra will then be able to use your suggestion and get completion super easily.
That make sense I forgot about non go (and non cobra) plugins, thanks I look forward to see how the helm completion extracted will look like !
I've posted something for people to try out in
It would be nice if some plugin developers try out the solution proposed in and provide feedback. since uses Cobra, the solution is very easy. Here is how to try it out: First build kubectl with the PR. Then create your completion script like this: put this new on $PATH. And now test using the newly built (I build mine at ). For completion of flags (which I realize is the real value for the plugin), kubectl needs to first move to Cobra 1.3.
I would be interested in your opinion on the proposed solution. It will not work out-of-the-box with Krew, but I haven't found a way to do better with respect to Krew. You had mentioned this previously, and although it would be a nice solution, I am concerned it would cause problems to any plugin that ignores all arguments and runs no matter what. With such a plugin, calling a command would trigger the plugin to run and possibly perform undesired actions when completions are requested.
I'm sorry about slow responses. Finally had time to read it and parse these. You're right we shouldn't randomly call a plugin binary without knowing it supports completion. From : kubectl already has a mechanism to find all plugins on $PATH, so I agree that at minimum, kubectl<kbdTab</kbdcan and should show plugins installed on the system (even if the plugins themselves don't support shell completion) I think this is a good model.

Just like how kubectl scans $PATH for , it can scan to see if a plugin supports completion. (It's important to define if that binary takes additional positional args or --options) To make the (2) a reality, I support adding an additional field to the Krew plugin manifest. The shape of that would be up for a discussion (I imagine it might be (a) a separate binary that comes in the plugin archive, or (b) allow linking to the plugin binary itself and the plugin reads argv[0] and prints completion, which can be done with (a) anyway). I think it's doable. I'm not very familiar with how shell completion works in practice, when it's called, how lazy can it be loaded, what are performance implications etc, but if you'd like to drive this effort, I think we can discuss a design on Krew side as well. Please bring this up in a SIG CLI meeting to see what the folks think about your proposal.
brilliant! Thanks for taking the time to think about this. Your suggestion to adapt krew sounds great to me. I will continue with the PR on kubectl's side and if it gets accepted we can look at krew.
The as proposed in accepts the exact same arguments as the standard executable. The new completion executable will examine those arguments and will determine what the shell completion choices following them should be.
do you have an insight into whether a plugin developer would develop and ship a separate executable for the completion, or would they simply link the main plugin executable and see if the argv[0] is the kubectl_complete-*? I assume the answer largely also depends on whether the plugin was authored in Go or bash (basically the only two languages I've ever seen a plugin submission in out of 150+).
I think plugins will choose to ship a separate executable. I feel it keeps the two aspects nicely separate (the plugin functionality and the shell completion functionality). Also, it is very easy for a separate executable to call back the main plugin if the developer wishes to do so, so I find that solution the most flexible. For example, for plugins using the Cobra library, the script would call back the executable like this: BTW, I have looked into the 179 plugins in the krew index and I found that 50% (yes, half!)

of them used Cobra (some of them indirectly by calling back ). This means that shell completion should be very easy to implement for all these plugins.
I'm interested in this support and thanks for adding this feature. One question: in which version this is planned to be released? Looking forward to this.