Docs example error: `Template parsing error`

[maxmorozoff]

Description

I need to List all port bindings in Docker so I found an example in documentation but in my case it throws an error.

Steps to reproduce the issue:

$ docker run --rm -itd --name documentation-issue mysql:5.7 bash
d24af5958f714cede788ae7db04abae2fc4e515d8fa32ce038583eebe8a9d540
$ docker inspect format='{{range $p, $conf := .NetworkSettings.Ports}}{{$p}} -> {(index $conf 0).HostPort}}{{end}}' documentation-issue

To stop container, execute:

$ docker stop documentation-issue 
documentation-issue

Describe the results you received:

Template parsing error: template: :1:75: executing "" at <index $conf 0>: error calling index: index of untyped nil

Describe the results you expected:

In go templates there is with action, using that everything works as expected:

$ docker inspect --format='{{range $p, $conf := .NetworkSettings.Ports}} {{$p}} -> {{with $conf}}{{(index . 0).HostPort}}{{else}}none{{end}} {{end}}' documentation-issue
mysql:5.7 3306/tcp -> none  33060/tcp -> none 

$ docker inspect --format='{{range $p, $conf := .NetworkSettings.Ports}} {{$p}} -> {{with $conf}}{{(index . 0).HostPort}}{{end}} {{end}}' documentation-issue
mysql:5.7 3306/tcp ->   33060/tcp ->  

Output of docker version:

Client:
 Version:           20.10.17
 API version:       1.41
 Go version:        go1.17.11
 Git commit:        100c701
 Built:             Mon Jun  6 22:56:42 2022
 OS/Arch:           linux/amd64
 Context:           default
 Experimental:      true

Server: Docker Engine - Community
 Engine:
  Version:          20.10.17
  API version:      1.41 (minimum version 1.12)
  Go version:       go1.17.11
  Git commit:       a89b842
  Built:            Mon Jun  6 23:01:23 2022
  OS/Arch:          linux/amd64
  Experimental:     false
 containerd:
  Version:          1.6.6
  GitCommit:        10c12954828e7c7c9b6e0ea9b0c02b01407d3ae1
 runc:
  Version:          1.1.2
  GitCommit:        v1.1.2-0-ga916309
 docker-init:
  Version:          0.19.0
  GitCommit:        de40ad0

Output of docker info:

Client:
 Context:    default
 Debug Mode: false
 Plugins:
  buildx: Docker Buildx (Docker Inc., v0.8.2)
  compose: Docker Compose (Docker Inc., v2.9.0)

Server:
 Containers: 126
  Running: 8
  Paused: 0
  Stopped: 118
 Images: 330
 Server Version: 20.10.17
 Storage Driver: overlay2
  Backing Filesystem: extfs
  Supports d_type: true
  Native Overlay Diff: true
  userxattr: false
 Logging Driver: json-file
 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 logentries splunk syslog
 Swarm: inactive
 Runtimes: io.containerd.runc.v2 io.containerd.runtime.v1.linux runc
 Default Runtime: runc
 Init Binary: docker-init
 containerd version: 10c12954828e7c7c9b6e0ea9b0c02b01407d3ae1
 runc version: v1.1.2-0-ga916309
 init version: de40ad0
 Security Options:
  apparmor
  seccomp
   Profile: default
  cgroupns
 Kernel Version: 5.10.0-13-amd64
 Operating System: Debian GNU/Linux 11 (bullseye)
 OSType: linux
 Architecture: x86_64
 CPUs: 8
 Total Memory: 23.37GiB
 Name: max-pc
 ID: D5HN:MTM3:BVNY:UFK2:62BI:EJLW:V3MG:FFKO:L3W4:JWH7:D5GV:TCYM
 Docker Root Dir: /var/lib/docker
 Debug Mode: false
 Registry: https://index.docker.io/v1/
 Labels:
 Experimental: false
 Insecure Registries:
  127.0.0.0/8
 Live Restore Enabled: false

Additional environment details (AWS, VirtualBox, physical, etc.):

[bsousaa]

I'm closing this issue in favour of the PR #3728. Feel free to re-open if needed.