Show Docker Context

[mattcen]

Docker now features contexts which allow the user to use Docker setups on remote hosts etc. For people who use this, it's useful to list in the prompt what context is currently active, so they know which environment Docker commands will affect.

Description

The prompt should show, somewhere, the name of the current Docker context, if it's not the default context.

How will this be useful?

To show which Docker environment will be affected by Docker commands

Example prompt

I'm not sure where best to display it, but somewhere in the prompt, with some appropriate symbol, display the text name of the current context. In the past, I've displayed this as (🐳myContext), but not all terminals support emoji, so perhaps a new symbol makes sense.

I've written some sample code to determine the current Docker context. If we're in the default context, the functions returns the empty string. Note that jq is required to parse the Docker config file, hence _lp_require_tool.

_lp_require_tool DOCKER_CONTEXT jq
 
_lp_docker_context()
{
    (( LP_ENABLE_DOCKER_CONTEXT )) || return
     local context
     context=$(jq -r .currentContext ~/.docker/config.json | grep -v null)
     echo "$context"
}

[Rycieos]

This is different than #569 right? Docker context is similar to Kubernetes context, not about which container you are in.

This is a valid request, and even better than you have included a suggested implementation. I don't know about using jq, but as we enter the post-json era, probably it will be needed for more parsing anyway, so I might accept that.

As with other features, this will have to wait until the rework is done, as Liquidprompt is currently too slow to accept any new features. Even disabled, each added feature will slow the prompt with how it works right now. But with an example implementation, this should be quick to implement.

[mattcen]

Correct; different issue to #569, and yes, similar to Kubernetes context I believe. Understood re rework; just wanted to follow the issue while I remembered. Also understand re jq; I tried to think of other ways to parse the json, but they're all hacks. Could probably fall back to Python which may be more likely to be installed, but that'd involve some nasty inline Python code.

[Rycieos]

Startup time of external commands will need to be compared. My guess is that jq will start up faster than most other tools.

[Rycieos]

Sorry for the radio silence on this.

I do not want to use jq. Nothing else in Liquidprompt depends on it, and it would make more sense to use nothing other than docker itself.

Unfortunately, docker context does not have any subcommand to print the current context. But, it does have docker context inspect, which (while not documented) does allow for calling it without an argument, and then it returns the data for the current context.

So, using this:

local context="$(docker context inspect)"
context="${context#*'"Name": "'}"
context="${context%%'",'*}"

We can get the name of the context. It's hacky, but we don't need any external tools.

Thoughts?

[mattcen]

I tend to try to avoid using hacky approaches like this, but I no longer use liquidprompt, so in this case I'm entirely indifferent.

[Rycieos]

Thanks for the honest feedback.

In that case, I will leave this open to see if it gathers other interest, but will not be working on a solution myself until then.