zsh autocompletion not replacing tabs correctly

[fandahao17]

What happened?

While using zsh autocompletion:

[fandahao@localhost]~% kubectl ge\t

No completion result is given.

When I turn on $BASH_COMP_DEBUG_FILE, I see the following logs:

========= starting completion logic ==========
CURRENT: 2, words[*]: kubectl ge
Truncated words[*]: kubectl ge,
lastParam: ge, lastChar: e
About to call: eval kubectl __complete ge
completion output: get	Display one or many resources
:4
last line: :4
directive: 4
completions: get	Display one or many resources
flagPrefix: 
Adding completion: :g:e:t:	:D:i:s:p:l:a:y: :o:n:e: :o:r: :m:a:n:y: :r:e:s:o:u:r:c:e:s

I noticed that the last line seems to give weird results. After printing out what source <(kubectl completion zsh) does, I think the bug is caused by the following lines:

            # If requested, completions are returned with a description.
            # The description is preceded by a TAB character.
            # For zsh's _describe, we need to use a : instead of a TAB.
            # We first need to escape any : as part of the completion itself.
            comp=${comp//:/\\:}

            local tab=$(printf '\t')
            comp=${comp//$tab/:}

The last line is supposed to replace all \t's in the completion result with :, but it actually replaced all empty strings with a :.

Replacing the last two lines with the following code seems to solve the problem:

comp=${comp//$(printf '\t')/:}

Honestly, I don't know why this works correctly while the original code does not. I guess tabs may need to be treated differently when doing variable expansions?

What did you expect to happen?

After modifying the code as in last section, I got the following logs. I think this is the correct result.

========= starting completion logic ==========
CURRENT: 2, words[*]: kubectl ge
Truncated words[*]: kubectl ge,
lastParam: ge, lastChar: e
About to call: eval kubectl __complete ge
completion output: get	Display one or many resources
:4
last line: :4
directive: 4
completions: get	Display one or many resources
flagPrefix: 
tab is ''
Adding completion: get:Display one or many resources

How can we reproduce it (as minimally and precisely as possible)?

[fandahao@localhost]~% zsh --version
zsh 5.0.2 (x86_64-redhat-linux-gnu)

A minimal .zshrc:

source <(kubectl completion zsh)

Anything else we need to know?

No response

Kubernetes version

Client Version: version.Info{Major:"1", Minor:"22", GitVersion:"v1.22.0", GitCommit:"c2b5237ccd9c0f1d600d3072634ca66cefdf272f", GitTreeState:"clean", BuildDate:"2021-08-04T18:03:20Z", GoVersion:"go1.16.6", Compiler:"gc", Platform:"linux/amd64"}
Server Version: version.Info{Major:"1", Minor:"22", GitVersion:"v1.22.0", GitCommit:"c2b5237ccd9c0f1d600d3072634ca66cefdf272f", GitTreeState:"clean", BuildDate:"2021-08-04T17:57:25Z", GoVersion:"go1.16.6", Compiler:"gc", Platform:"linux/amd64"}

Cloud provider

This bug happens on my own machine.

OS version

[fandahao@localhost]~% cat /etc/os-release
NAME="CentOS Linux"
VERSION="7 (Core)"
ID="centos"
ID_LIKE="rhel fedora"
VERSION_ID="7"
PRETTY_NAME="CentOS Linux 7 (Core)"
ANSI_COLOR="0;31"
CPE_NAME="cpe:/o:centos:centos:7"
HOME_URL="https://www.centos.org/"
BUG_REPORT_URL="https://bugs.centos.org/"

CENTOS_MANTISBT_PROJECT="CentOS-7"
CENTOS_MANTISBT_PROJECT_VERSION="7"
REDHAT_SUPPORT_PRODUCT="centos"
REDHAT_SUPPORT_PRODUCT_VERSION="7"

[fandahao@localhost]~% uname -a
Linux localhost.localdomain 5.4.146-1.el7.elrepo.x86_64 #1 SMP Tue Sep 14 08:38:01 EDT 2021 x86_64 x86_64 x86_64 GNU/Linux

Install tools

Container runtime (CRI) and and version (if applicable)

Related plugins (CNI, CSI, ...) and versions (if applicable)

[k8s-ci-robot]

@fandahao17: This issue is currently awaiting triage.

If a SIG or subproject determines this is a relevant issue, they will accept it by applying the triage/accepted label and provide further guidance.

The triage/accepted label can be added by org members by writing /triage accepted in a comment.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[fandahao17]

/sig cli

[brianpursley]

This appears to be related to which zsh version you are using.

At first, I was unable to reproduce the problem, but then realized I have zsh 5.8.

So I downloaded and built zsh 5.0.2 to match the version @fandahao17 reported using and am able to reproduce the problem.

@fandahao17 Are you able to upgrade to a newer version of zsh? 5.8 worked for me, but I don't know if an earlier version might also work.

We should probably figure out what the minimum required version is for zsh completions to work and document it.

[marckhouzam]

I am also able to reproduce this using Zsh 5.0.x.
Based on @brianpursley realizing this has to do with the version of zsh, I was able to find that the problem disappears with zsh 5.1 (testing was made much easier thanks to https://github.com/zsh-users/zsh-docker)

I can also confirm that the suggested fix does seem to work.

@fandahao17 The fix you found is simple enough that it may be worth opening an issue with the https://github.com/spf13/cobra project which generates the completion scripts to try to get it in.

[eddiezane]

Please open over on the cobra repo if you'd like to get this fixed there.

/close

[k8s-ci-robot]

@eddiezane: Closing this issue.

In response to this:

Please open over on the cobra repo if you'd like to get this fixed there.

/close

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[marckhouzam]

A fix for this issue will be part of the next Cobra release: spf13/cobra#1665

[brneto]

I've created the PR #112362 to fix this issue, but for those still facing this issue after installing Oh My Zsh with kubectl plugin enabled you can run the command below as a patch to fix it in the meantime:

sed -i '6i\    sed -i '\''s/tab=$(printf \x27\\t\x27)/tab="$(printf \x27\\t\x27)"/'\'' "$ZSH_CACHE_DIR/completions/_kubectl"\' ~/.oh-my-zsh/plugins/kubectl/kubectl.plugin.zsh && \
sed -i '9i\    sed -i '\''s/tab=$(printf \x27\\t\x27)/tab="$(printf \x27\\t\x27)"/'\'' "$ZSH_CACHE_DIR/completions/_kubectl"\' ~/.oh-my-zsh/plugins/kubectl/kubectl.plugin.zsh && \
sed -i '12i\    sed -i '\''s/tab=$(printf \x27\\t\x27)/tab="$(printf \x27\\t\x27)"/'\'' "$ZSH_CACHE_DIR/completions/_kubectl"\' ~/.oh-my-zsh/plugins/kubectl/kubectl.plugin.zsh && \
exec zsh