Add shell completions

[itowlson]

I had a quick play with this to see what it could give us and there is good news and there is bad news.

The good news is that we can get completions for things like commands and options. E.g. spin de<TAB> -> spin deploy, spin new --va<TAB> -> --value --values-file.

The bad news is that nothing else really works - at least on bash. (Maybe it would have worked better on zsh.) All value completions seem to be "any path." clap_complete supports a bunch of value hints but ignores all of them, or at least all the ones I tried. For example, ValueHint::FilePath, ValueHint::DirPath and ValueHint::Url all resolve to compgen -f which is files and directories. I don't know if this is fixed in more recent versions of clap_complete, but I did find an issue where people were asking for dynamic completions (e.g. spin template new <TAB> and it would give you a list of templates) and it wasn't happening.

In this draft, the user experience is bad news too. You would run spin generate-completions {bash|zsh|...} >spincomps, then chmod +x spincomps, then add source spincomps to your .bashrc or user completions file or something like that. Then you upgrade Spin and do the dance again. If we think command and option completion is worth it, we can discuss a better UI, and whether to support other shells.

And right now the code is also bad news, but I wanted to get opinions on whether we wanted this and if so what we wanted it to look like before I invested in niceing it up.

Signed-off-by: itowlson [email protected]

[kate-goldenring]

@itowlson I wasn't able to get the flow working on my end. I did the following:

cargo build
./target/debug/spin generate-bash-completions > ~/spincomps
echo "sourch spincomps" >> ~/.bashrc
# fails to autocomplete `spin deploy`
./target/debug/spin de

Am i missing a step?

[itowlson]

@kate-goldenring It looks like it only works if spin is unqualified (i.e. on the PATH). I see the same thing if I try to autocomplete via a relative path. CURSES.

[itowlson]

I dunno if this is a bash limitation or if there is an incantation we can do to make it behave properly.

[itowlson]

Kate reports that it now blows up on zsh with _arguments:comparguments:325: can only be called from completion function so not sure how to proceed from here... might have to call it a day!

[itowlson]

All right, it looks like on zsh you need to pipe it to a file named _spin and put this into .zshrc (assuming you put the file in a ~/completions directory):

autoload -Uz compinit
fpath=(~/completions $fpath)
compinit

Thanks @kate-goldenring for working through this!

[mikkelhegn]

I wanted to tru this in my Fish shell, but got stuck here:

spin generate-bash-completions > ~/spincomps
Unknown command: plugin 'generate-bash-completions' not found at expected location /Users/mikkel/Library/Application Support/spin/plugins/manifests/generate-bash-completions.json: No such file or directory (os error 2)

I've built the debug version from this PR branch.

[mikkelhegn]

As a totally unrelated side-note, I just realized the word play of having a Fish shell!!! Have only been using thing thing for at least two years now...

[kate-goldenring]

I wanted to tru this in my Fish shell, but got stuck here:

spin generate-bash-completions > ~/spincomps
Unknown command: plugin 'generate-bash-completions' not found at expected location /Users/mikkel/Library/Application Support/spin/plugins/manifests/generate-bash-completions.json: No such file or directory (os error 2)

I've built the debug version from this PR branch.

@mikkelhegn I believe it has been renamed to remove bash: spin generate-completions > ~/spincomps

[itowlson]

@mikkelhegn I updated the description without leaving a comment; my bad. I changed the syntax to spin generate-completions <SHELL> because my first tester used zsh not bash. I think fish is supported but have lost all confidence in how you actually wire up the generated completion file...!

[radu-matei]

Paging @bacongobbler and @adamreese, who might have more background on building completions for CLIs.

[adamreese]

Thanks for getting this started. We should exclude hidden commands like spin trigger (and the recursive spin generate-completions)

Adding completers for commands like spin new http<TAB> would be great but isn't needed for the first iteration

[mikkelhegn]

Works nicely in fish

spin generate-completions fish > ~/.config/fish/completions/spin.fish

[mikkelhegn]

@itowlson - Is this something we could consider for 2.0?

[itowlson]

@mikkelhegn The question, for me, is: given what we now know about the limitations of doing it the quick way, and the cost of doing it a nicer way, how do we want to proceed:

1. The quick way is too limited, and the nice way too costly, to be worth it. Leave it for now.
2. The quick way is limited, but better than nothing - do it that way.
3. The feature is worth the cost of doing it right - invest in the nice way.

We can then define what we want the user experience to be (e.g. the generate-completions dump command or something fancier).

This is independent of 2.0 (at least at the technical level) - nothing in this would involve breaking changes as far as I know.

[mikkelhegn]

My preference, stack ranked would be:

3, 2, 1 :-) I'll leave it to the overall prioritization for the team to decide if this is above the cut line.

I think we should have some completion in 2.0 (as the project now starts to really mature). Will either of the above also work for plug-ins out-of-the-box?

[itowlson]

The quick way won't for plugins, though with the Clap shenanigans in #1560 it might list initial plugin names - but it is purely static, derived from the Clap command structures.

The nice way... who knows? I wouldn't be optimistic, and at minimum it would depend on the plugin providing a way to
get completions that we could then fold into our completions (or hand off to the plugin to complete). I don't know enough about completions to be sure if or how this might work.

[mikkelhegn]

Another effort related to this: https://github.com/karthik2804/spin-autocomplete @karthik2804 @itowlson