Make snippet available only if TM_SELECTED_TEXT has a value

[Samasaur1]

Let's say I have a Swift snippet called printv, with the end result looking like this:

print("myvar=\(myvar)")

I want to be able to use it three separate ways:

1. Standalone

    s({
        trig="printv",
        name="printv-standalone",
        dscr="Print [type here]=<value>",
    }, {
        t("print(\""),
        rep(1),
        t("=\\("),
        i(1),
        t(")\")")
    }),

You type printv on an empty line and it expands to let you type in the name of the variable, which it then duplicates.
2. With selection

    s({
        trig="printv",
        name="printv-selection",
        dscr="Print 'selected variable'=<value>",
    }, {
        t('print("'),
        f(function(_, snip)
            -- TM_SELECTED_TEXT is a table to account for multiline-selections.
            --          -- In this case only the first line is inserted.
            return snip.env.TM_SELECTED_TEXT[1] or {}
        end, {}),
        t('=\\('),
        f(function(_, snip)
            -- TM_SELECTED_TEXT is a table to account for multiline-selections.
            --          -- In this case only the first line is inserted.
            return snip.env.TM_SELECTED_TEXT[1] or {}
        end, {}),
        t(')")')
    }),

Select an expression (e.g., viw), hit Tab (in my case, since

luasnip.config.set_config({
    store_selection_keys="<Tab>",
})

), then type printv and it will fill in the selection.
3. Postfix
I haven't written it yet, but I don't think it will be too complicated.

---

My question is about trying to get only one of these to show up at a time. If you type printv on a blank line, both printv-standalone and printv-selection show up. I'd like to have them set up so that, if TM_SELECTED_TEXT is empty, I only see printv-standalone, and if TM_SELECTED_TEXT has a value, I only see printv-selection. I'm not sure exactly how a postfix version will fit into the mix, because I haven't written that yet either, but I'd like it to also be disambiguated.

Is this possible?

[L3MON4D3]

Oh, nice, that's definitely possible. I'll list some ingredients :D

• condition/show_condition can hide a snippet (first for regular expansion, second for completion engines)
• You can basically just write a show_condition and pass it to both options (they're compatible with both), oviously negated for one snippet (recommending condition_objects for doing that in a readable fashion)
• There's currently no api for getting the selection that would be consumed by the next snippet, but you can just rely on the implementation, it's unlikely to change (Basically, the selection is stored in a buffer-local variable, you can just check if it exists via pcall like in the linked function) (don't call get_selection itself though, it will consume the selection (is inappropriately named, s/get/consume/ 😅))

Alternative approach: wrap the entire snippet in a dynamicNode which checks if there was selected text, and returns one or the other (could also be used for postfix, by checking its variable as well)

Oh or!: use TM_SELECTED_TEXT as the preset text for the insertNodes in the first snippet, then you should also have all in one, I think, and could do it with just parse: "visual or empty: ${1:$TM_SELECTED_TEXT}"

[Samasaur1]

I think I can get the standalone and selection versions to only appear in non-postfix contents by changing it to a regTrig (I'm not sure which postfix variable you're talking about to check)

[L3MON4D3]

Even when I select something first, and then type pv and expand the snippet, it still goes with the else clause, and I don't know why.

Mhmm, that's weird, I can't spot anything wrong.. try verifying that the selection is actually populated

[L3MON4D3]

(I'm not sure which postfix variable you're talking about to check)

I meant POSTFIX_MATCH, but I was thinking completely along the wrong lines 😅

[Samasaur1]

Even when I select something first, and then type pv and expand the snippet, it still goes with the else clause, and I don't know why.

Mhmm, that's weird, I can't spot anything wrong.. try verifying that the selection is actually populated

I'm pretty sure the selection is actually populated — my other snippets that use selection still work. Here's a GIF of me using this new dynamicNode based snippet, which doesn't work for selections, compared to the working selection snippet above.

[L3MON4D3]

weird.. Try monitoring the returned values via print (in the dynamicNode)

[Samasaur1]

For completeness, here's the postfix version:

    require("luasnip.extras.postfix").postfix(".printv", {
        t("print(\""),
        l(l.POSTFIX_MATCH),
        t("=\\("),
        l(l.POSTFIX_MATCH),
        t(")\")"),
        i(0)
    }),