x/tools/gopls: feature request: adding postfix snippets for errors

[urandom]

gopls version

golang.org/x/tools/gopls v0.7.4

Would it be possible to add postfix snippets that are specific for the error type.

I was thinking something like:

err.if!

// Which would expand to:

if err != nil {
    |
}

I guess this one could be uses for any type, not just an error, though maybe the snippet name should be better (ifNot!?)

and a more complex one that returns and takes into account the other return types:

func MyFunc() (*Ptr, int, error) {
    ...

    err.ret!

    // Which would expand to:
    if err != nil {
         return nil, 0, fmt.Errorf("|: %w", err)  
    }
}

[muirdm]

You can get something similar via statement completions. Does that satisfy your use cases?

[urandom]

These statement completions seem to be quite old, but I've never seen them being offered as part of any completion request.

I just checked what is currently being returned, and this is not part of the result:

I also installed vscode, in case neovim somehow didn't support this, but the result is the same:

According to the diff, this requires placeholders, but adding usePlaceholders to both vscode and neovim didn't make a difference for the results, though I'm not sure that placeholders are worth it for me even for this feature (they require a different workflow from what I'm used to)

[muirdm]

It should work in any client that supports snippets (do you have snippets disabled?). What does your VSCode go config look like?

This is an example where I see it:

[urandom]

Snippets are enabled and working in both neovim and vscode. Both non lsp snippets and ones coming from gopls. The latter was quite visible when I enabled placeholders and was able to jump between the various positions.

The vscode config is empty (fresh install to test this), except for the 3 lines needed to enable placeholders. I'm not in front of a computer right now, so I can't actually post it.

Edit: settings.json:

{
    "gopls": {
        "ui.completion.usePlaceholders": true,
    }
}

[muirdm]

I see the if err != nil completion in VS Code with just the usePlaceholders:true setting. Note that it only shows up if "err" was assigned in the previous statement, and if the enclosing function's last return value is an error.

[thepudds]

FWIW, I do see these with the following added to settings.json:

    "gopls": {
        "ui.completion.usePlaceholders": true,
    }

It would be nice if the if err statement completion was enabled by default.

I would be interested in sending a CL enable this by default if that is considered an appropriate change. (That might be a small change for a seasoned gopls contributor, but it would be an opportunity for me to learn more about contributing to gopls).

edit: corrected initial comment (incorrect setting).

[thepudds]

And I guess there are at least two ways to enable this by default:

1. Change the default of "ui.completion.usePlaceholders" to true rather than defaulting off, but that might be a bigger change?
2. Change the logic of if err statement completion to issue a completion without relying on any placeholders if c.opts.placeholders is false? Currently, it just returns:

func (c *completer) addErrCheckAndReturn() {
	if len(c.path) < 2 || c.enclosingFunc == nil || !c.opts.placeholders {
		return
	}

[muirdm]

Either makes sense to me. 1) will be contentious, but that is how it defaults already in Emacs lsp-mode. 2) should be easy, but note that I required placeholders so that the "err" in "return err" would be selected on insertion, making it easier to wrap/contextualize the error.

There is option 3) which is to ignore the usePlaceholders setting in this case and always give a placeholder. This use of placeholders is pretty benign and may not annoy users like the func call placeholders do.

[timsofteng]

How about just ir?

[thepudds]

Just a quick update: I have a basic change (in line with what @muirdm suggested), as well as looking at a slightly larger change, but I’ll probably break the second piece into a separate issue…