CC @robpike

This adds no functionality, it is just a convenience. One may argue that it should be done for consistency, and it's not difficult although every change has costs (and for templates, they are doubled because of html/template). I am not convinced it is worth doing but I am not adamant.

It's just a convenience for if/else too.

This is real code:

{{ with $page.Resources.GetMatch $url }}
    {{ $result = . }}
{{ else }}
    {{ with $page.Resources.Get $url }}
        {{ $result = . }}
    {{ else }}
        {{ with resources.GetMatch $url }}
            {{ $result = . }}
        {{ else }}
            {{ with resources.Get $url }}
                {{ $result = . }}
            {{ else }}
                {{ with resources.GetRemote $url }}
                    {{ $result = . }}
                {{ end }}
            {{ end }}
        {{ end }}
    {{ end }}
{{ end }}

Compare that to:

{{ with $page.Resources.GetMatch $url }}
    {{ $result = . }}
{{ else with $page.Resources.Get $url }}
    {{ $result = . }}
{{ else with resources.GetMatch $url }}
    {{ $result = . }}
{{ else with resources.Get $url }}
    {{ $result = . }}
{{ else with resources.GetRemote $url }}
    {{ $result = . }}
{{ end }}

The difference might seem trivial if you're used to only touching templates occasionally or superficially, but it's a big quality of life improvement for those who spend hours writing non-trivial programs in templates, like authors of Hugo themes/modules.

or you could format your existing code like this

{{ with $page.Resources.GetMatch $url }}
    {{ $result = . }}
{{ else }}{{ with $page.Resources.Get $url }}
    {{ $result = . }}
{{ else }}{{ with resources.GetMatch $url }}
    {{ $result = . }}
{{ else }}{{ with resources.Get $url }}
    {{ $result = . }}
{{ else }}{{ with resources.GetRemote $url }}
    {{ $result = . }}
{{ end }}{{ end }}{{ end }}{{ end }}{{ end }}

It's not the shape of the code that's important, it's the complexity. {{ else }}{{ with is harder to read and reason about. How can you even tell if {{ end }}{{ end }}{{ end }}{{ end }}{{ end }} has enough end's without counting them?

@seankhliao there's no sane template formatter (e.g.: https://github.com/NiklasPor/prettier-plugin-go-template) that would format the template source the way you suggest, and throwing a way automatic template formatting is not something anyone would want to do.

I agree with proposal. It should be of tremendous value (save lots of end user time) compared to the time spent on implementing it. I suspect that the people who say "thumbs down" to this are people who really don't spend any amount of time writing Go templates.

Given the use cases presented here, this seems OK to do.

This proposal has been added to the active column of the proposals project
and will now be reviewed at the weekly proposal review meetings.
— rsc for the proposal review group

Based on the discussion above, this proposal seems like a likely accept.
— rsc for the proposal review group

No change in consensus, so accepted. 🎉
This issue now tracks the work of implementing the proposal.
— rsc for the proposal review group

Change https://go.dev/cl/545376 mentions this issue: text/template: add "else with" action

This issue is currently labeled as early-in-cycle for Go 1.23.
That time is now, so a friendly reminder to look at it again.