CLI completion has weird bugs

[bartekpacia]

Description

When I type docker into my terminal and click <TAB>, I see some weird stuff:

https://github.com/docker/cli/assets/40357511/20cf40e7-daa7-48df-8028-1e7485619607

Reproduce

(Forgive me for assuming macOS and Homebrew)

1. brew install --cask docker
2. Make sure completion setup code is present in ~/.zshrc:

FPATH="$(brew --prefix)/share/zsh/site-functions:$FPATH"

Expected behavior

When I type docker and click <TAB>, I expect to see only commands:

• no --flags

• no garbled output like the first and last line, e.g.:

  $ docker
  "warn",                            -- "error", "fatal") (default "info")
  

docker version

Client:
 Cloud integration: v1.0.35+desktop.11
 Version:           25.0.3
 API version:       1.44
 Go version:        go1.21.6
 Git commit:        4debf41
 Built:             Tue Feb  6 21:13:26 2024
 OS/Arch:           darwin/arm64
 Context:           desktop-linux

Server: Docker Desktop 4.28.0 (139021)
 Engine:
  Version:          25.0.3
  API version:      1.44 (minimum version 1.24)
  Go version:       go1.21.6
  Git commit:       f417435
  Built:            Tue Feb  6 21:14:22 2024
  OS/Arch:          linux/arm64
  Experimental:     false
 containerd:
  Version:          1.6.28
  GitCommit:        ae07eda36dd25f8a1b98dfbf587313b99c0190bb
 runc:
  Version:          1.1.12
  GitCommit:        v1.1.12-0-g51d5e94
 docker-init:
  Version:          0.19.0
  GitCommit:        de40ad0

docker info

Client:
 Version:    25.0.3
 Context:    desktop-linux
 Debug Mode: false
 Plugins:
  buildx: Docker Buildx (Docker Inc.)
    Version:  v0.12.1-desktop.4
    Path:     /Users/bartek/.docker/cli-plugins/docker-buildx
  compose: Docker Compose (Docker Inc.)
    Version:  v2.24.6-desktop.1
    Path:     /Users/bartek/.docker/cli-plugins/docker-compose
  debug: Get a shell into any image or container. (Docker Inc.)
    Version:  0.0.24
    Path:     /Users/bartek/.docker/cli-plugins/docker-debug
  dev: Docker Dev Environments (Docker Inc.)
    Version:  v0.1.0
    Path:     /Users/bartek/.docker/cli-plugins/docker-dev
  extension: Manages Docker extensions (Docker Inc.)
    Version:  v0.2.22
    Path:     /Users/bartek/.docker/cli-plugins/docker-extension
  feedback: Provide feedback, right in your terminal! (Docker Inc.)
    Version:  v1.0.4
    Path:     /Users/bartek/.docker/cli-plugins/docker-feedback
  init: Creates Docker-related starter files for your project (Docker Inc.)
    Version:  v1.0.1
    Path:     /Users/bartek/.docker/cli-plugins/docker-init
  sbom: View the packaged-based Software Bill Of Materials (SBOM) for an image (Anchore Inc.)
    Version:  0.6.0
    Path:     /Users/bartek/.docker/cli-plugins/docker-sbom
  scout: Docker Scout (Docker Inc.)
    Version:  v1.5.0
    Path:     /Users/bartek/.docker/cli-plugins/docker-scout

Server:
 Containers: 0
  Running: 0
  Paused: 0
  Stopped: 0
 Images: 10
 Server Version: 25.0.3
 Storage Driver: overlay2
  Backing Filesystem: extfs
  Supports d_type: true
  Using metacopy: false
  Native Overlay Diff: true
  userxattr: false
 Logging Driver: json-file
 Cgroup Driver: cgroupfs
 Cgroup Version: 2
 Plugins:
  Volume: local
  Network: bridge host ipvlan macvlan null overlay
  Log: awslogs fluentd gcplogs gelf journald json-file local splunk syslog
 Swarm: inactive
 Runtimes: io.containerd.runc.v2 runc
 Default Runtime: runc
 Init Binary: docker-init
 containerd version: ae07eda36dd25f8a1b98dfbf587313b99c0190bb
 runc version: v1.1.12-0-g51d5e94
 init version: de40ad0
 Security Options:
  seccomp
   Profile: unconfined
  cgroupns
 Kernel Version: 6.6.16-linuxkit
 Operating System: Docker Desktop
 OSType: linux
 Architecture: aarch64
 CPUs: 8
 Total Memory: 7.755GiB
 Name: docker-desktop
 ID: 31725210-46cb-4bf3-a925-18c0412459d5
 Docker Root Dir: /var/lib/docker
 Debug Mode: false
 HTTP Proxy: http.docker.internal:3128
 HTTPS Proxy: http.docker.internal:3128
 No Proxy: hubproxy.docker.internal
 Experimental: false
 Insecure Registries:
  hubproxy.docker.internal:5555
  127.0.0.0/8
 Live Restore Enabled: false

[zzJinux]

Digging a bit, I discovered that the unusual output arises from the interplay between how global flags are printed and how the zsh completion script (_docker) parses the output.

This is how you see the output:

1. You invoke docker <tab>.
2. _docker executes docker to get and parse the help output (I'll explain in more detail below). https://github.com/docker/cli/blob/4debf411d1e6efbd9ce65e4250718e9c529a6525/contrib/completion/zsh/_docker#L2652-L2653
3. zsh prints the output to the user.

In step 2, docker is executed in an environment where the width of its terminal cannot be retrieved, in which case docker falls back assuming the width is 80.

https://github.com/docker/cli/blob/4debf411d1e6efbd9ce65e4250718e9c529a6525/cli/cobra.go#L344-L350

The wrappedFlagUsages is called for printing options in Global Options section. Every single line is wrapped to fit the width 80. Instead of this:

_call_program commands docker 2>&1 outputs the:

(... commands section ...)
Global Options:
      --config string      Location of client config files (default
                           "/Users/zzjinux/.docker")
  -c, --context string     Name of the context to use to connect to the
                           daemon (overrides DOCKER_HOST env var and
                           default context set with "docker context use")
  -D, --debug              Enable debug mode
  -H, --host list          Daemon socket to connect to
  -l, --log-level string   Set the logging level ("debug", "info",
                           "warn", "error", "fatal") (default "info")
      --tls                Use TLS; implied by --tlsverify
      --tlscacert string   Trust certs signed only by this CA (default
                           "/Users/zzjinux/.docker/ca.pem")
      --tlscert string     Path to TLS certificate file (default
                           "/Users/zzjinux/.docker/cert.pem")
      --tlskey string      Path to TLS key file (default
                           "/Users/zzjinux/.docker/key.pem")
      --tlsverify          Use TLS and verify the remote
  -v, --version            Print version information and quit

The following line parses the output _assuming each option is confined within one line (it's not), and _docker_commands array stores a broken result:

(... commands section ...)
--config:string      Location of client config files (default
"/Users/zzjinux/.docker")
-c,:--context string     Name of the context to use to connect to the
daemon:(overrides DOCKER_HOST env var and
default:context set with "docker context use")
-D,:--debug              Enable debug mode
-H,:--host list          Daemon socket to connect to
-l,:--log-level string   Set the logging level ("debug", "info",
"warn",:"error", "fatal") (default "info")
--tls:Use TLS; implied by --tlsverify
--tlscacert:string   Trust certs signed only by this CA (default
"/Users/zzjinux/.docker/ca.pem")
--tlscert:string     Path to TLS certificate file (default
"/Users/zzjinux/.docker/cert.pem")
--tlskey:string      Path to TLS key file (default
"/Users/zzjinux/.docker/key.pem")
--tlsverify:Use TLS and verify the remote
-v,:--version            Print version information and quit

"warn",:"error", "fatal") (default "info") now appears. The zsh completion system interprets it as ""warn", is the keyword, and "errors", ... is the description".

I think we have two ways to solve this:

1. Deceive docker into thinking it's in a wider terminal. _call_program commands docker 2>&1 should be tweaked.
2. Change the behavior of docker to print help unwrapped when it fails to retrieve the width (By the way, only the Global Options section is affected by the terminal width. I don't know why).

@thaJeztah Is there any option more desirable?

[zzJinux]

@thaJeztah Wow, so fast adding the label!

[zzJinux]

https://github.com/zsh-users/zsh/blob/master/Completion/Base/Utility/_call_program

Respecting the COLUMNS environment variable seems a reasonable option too.