Autocomplete stopped working for `pull` command

[marcosox]

Description

After latest updates (I can't pinpoint the exact version but it was in the last ~6 months) the docker pull <TAB> <TAB> command doesn't do anything, while it was showing locally cached images before. All other autocomplete commands appear to work normally as before.

Reproduce

1. docker pull hello-world
2. docker pull he<TAB><TAB>
3. nothing happens

Expected behavior

Pressing TAB provides a list of locally cached images with the same exact behavior of docker run

docker version

Client: Docker Engine - Community
 Version:           28.3.3
 API version:       1.51
 Go version:        go1.24.5
 Git commit:        980b856
 Built:             Fri Jul 25 11:34:04 2025
 OS/Arch:           linux/amd64
 Context:           default

Server: Docker Engine - Community
 Engine:
  Version:          28.3.3
  API version:      1.51 (minimum version 1.24)
  Go version:       go1.24.5
  Git commit:       bea959c
  Built:            Fri Jul 25 11:34:04 2025
  OS/Arch:          linux/amd64
  Experimental:     false
 containerd:
  Version:          1.7.27
  GitCommit:        05044ec0a9a75232cad458027ca83437aae3f4da
 runc:
  Version:          1.2.5
  GitCommit:        v1.2.5-0-g59923ef
 docker-init:
  Version:          0.19.0
  GitCommit:        de40ad0

docker info

Client: Docker Engine - Community
 Version:    28.3.3
 Context:    default
 Debug Mode: false
 Plugins:
  buildx: Docker Buildx (Docker Inc.)
    Version:  v0.26.1
    Path:     /usr/libexec/docker/cli-plugins/docker-buildx
  compose: Docker Compose (Docker Inc.)
    Version:  v2.39.1
    Path:     /usr/libexec/docker/cli-plugins/docker-compose

Server:
 Containers: 5
  Running: 4
  Paused: 0
  Stopped: 1
 Images: 119
 Server Version: 28.3.3
 Storage Driver: overlay2
  Backing Filesystem: extfs
  Supports d_type: true
  Using metacopy: false
  Native Overlay Diff: true
  userxattr: false
 Logging Driver: local
 Cgroup Driver: systemd
 Cgroup Version: 2
 Plugins:
  Volume: local
  Network: bridge host ipvlan macvlan null overlay
  Log: awslogs fluentd gcplogs gelf journald json-file local splunk syslog
 CDI spec directories:
  /etc/cdi
  /var/run/cdi
 Swarm: inactive
 Runtimes: io.containerd.runc.v2 runc
 Default Runtime: runc
 Init Binary: docker-init
 containerd version: 05044ec0a9a75232cad458027ca83437aae3f4da
 runc version: v1.2.5-0-g59923ef
 init version: de40ad0
 Security Options:
  apparmor
  seccomp
   Profile: builtin
  userns
  cgroupns
 Kernel Version: 6.8.0-79-generic
 Operating System: Ubuntu 22.04.5 LTS
 OSType: linux
 Architecture: x86_64
 CPUs: 16
 Total Memory: 23.1GiB
 Name: [redacted]
 ID: 4ed36754-d593-4662-8c4d-d286f076bfea
 Docker Root Dir: /var/lib/docker/1000.999
 Debug Mode: false
 Username: [redacted]
 Experimental: false
 Insecure Registries:
  ::1/128
  127.0.0.0/8
 Live Restore Enabled: false

Additional Info

$ docker __complete pull he
:4
Completion ended with directive: ShellCompDirectiveNoFileComp
$ docker __complete run he
<list of all my local images>
:4
Completion ended with directive: ShellCompDirectiveNoFileComp

[thaJeztah]

Thanks for reporting! I had a quick peek to see if we possibly removed that completion, but it looks like completion was explicitly disabled already in v23.0
https://github.com/docker/cli/blob/v23.0.0/cli/command/image/pull.go#L42

That was added in 66b9056 to prevent the default (complete from local files) to be used.

I think the builtin (generated) completion never provided completion for docker pull, but having a quick look at the manually written completion scripts that were used before that, I see it does;

cli/contrib/completion/bash/docker

Lines 3052 to 3075 in 5bce5e1

	_docker_image_pull() {
	case "$prev" in
	--platform)
	return
	;;
	esac
	case "$cur" in
	-*)
	local options="--all-tags -a --disable-content-trust=false --help --platform --quiet -q"
	COMPREPLY=( $( compgen -W "$options" -- "$cur" ) )
	;;
	*)
	local counter=$(__docker_pos_first_nonflag --platform)
	if [ "$cword" -eq "$counter" ]; then
	for arg in "${COMP_WORDS[@]}"; do
	case "$arg" in
	--all-tags|-a)
	__docker_complete_images --repo
	return
	;;
	esac
	done
	__docker_complete_images --repo --tag

That would probably explain; we switched the default to use the generated completion functions in our packaging in docker/docker-ce-packaging#1150, which was around January.

Adding completion should be an easy fix; I think the completion was disabled with the assumption for docker pull to be used to pull new images (and trying to call the registry "search" API would not be possible for all registries), but having it complete with images you already have so that you can pull the latest version of the same tag makes sense, so I think we should indeed add that completion.

Let me have a quick look to add it; possibly it can still make it for the 28.4 release.

[thaJeztah]

Opened a PR #6419 (and prepared a backport for the 28.4 release)

[marcosox]

Thanks for the quick feedback, resolution and detailed explanation!

having it complete with images you already have so that you can pull the latest version of the same tag

I can confirm that this was the previous behavior (and basically my only use case for pull). I didn't even notice it until I realized I'm not used to typing the entire url of my private registry while updating my images

[thaJeztah]

Yes, that makes a lot of sense! And if you find other tab-completions that worked before but no longer do, please report them!

For a slight bit of context; the manually maintained tab-completion scripts for Bash were of very high quality, but the ones for other shells often fell behind; with various cli-plugins arriving (commands like docker compose, docker buildx, docker model are maintained as separate projects and separate binaries), maintaining manually written completion scripts was not sustainable, so we switched to tab-completion provided by the binaries themselves when we had most of the completions implemented, but we knew there would still be some gaps to address, so if you find more; please report ❤️