Multiple lines in insert node should have indentation of first line

[oiiiiiiii]

This problem is best described with an example: Say I have this snippet:

s("example", fmta([[
    if <> {
        <>
    }
    ]], { i(1), i(2, { "first line", "second line" }) }
))

When I expand it, I get

if | {
   first line
second line
} 

(where "|" is the cursor) but I would instead expect

if | {
   first line
   second line
} 

I know I could change "second line" to "\tsecond line", but the lines are not fixed but come from vim.split(parent.snippet.env.LS_SELECT_DEDENT, "\n"). I don't find it very intuitiv, that following lines have an indentation different from the first and would propose to change that.

[L3MON4D3]

Ah, check out indent_snippet_node, it can prefix all new lines of some node with a string (eg. \t)

[oiiiiiiii]

Yes that's true, but I find it a bit annoying to specify that every time. And creating a custom wrapper function would only work if the indent is always the same and not multiple levels deep. I would prefer to use the indent snippet node only if I do (for some reason) not want the indent to be the same as the first line as this seems like the much rarer usecase to me.

[L3MON4D3]

I think we can add an option to fmt to enable something like this (if there is only whitespace before some node, create an isn and wrap the mode with it).
I don't think I'd like to add this automatic indent to other parts of luasnip because it's (to me, but I also have more knowledge of what's going on under hood😅) unexpected. So I'd like for it to stay something one enables on purpose and isn't confused by :)

Regardless, what are you referring to with the custom wrapper, could you show me an example where that goes badly?

[oiiiiiiii]

What I meant is when I write a wrapper something like this:

local function ii(idx, placeholder)
  return isn(idx, i(1, placeholder), "$PARENT_INDENT\t")
end

i can use this instead of "i" when I only indent one level, but for two levels, like in a nested LaTeX environment, it would be this, so I would need to write another wrapper:

\begin{env1}
    \begin{env2}
        first line
    second line
    \end{env2}
\end{env1}

I think having that option in fmt would be really cool, but I can also see that it's maybe not the highest priority :D

[L3MON4D3]

Ah, I see...

I've looked into it a bit, and one way to make this function work pretty well for all current node-types is this:

local function ind(node, level)
	level = level or 1
    local indentstring = ("\t"):rep(level)
    if node.pos then
		local isnpos = node.pos
		node.pos = 1
		return isn(isnpos, {node}, "$PARENT_INDENT" .. indentstring)
	elseif node.type == types.functionNode then
		return f(function(...)
			local user_res = node.fn(...)
			for i = 2, #user_res do
				user_res[i] = indentstring .. user_res[i]
			end
			return user_res
		end, node.args, {user_args = node.user_args, key = node.key, node_callbacks = node.node_callbacks})
	elseif node.type == types.textNode then
		-- at this point node.static_text is not indented, that happens at
		-- runtime.
		local nodetext = node.static_text
		for i = 2, #nodetext do
			nodetext[i] = indentstring .. nodetext[i]
		end
		return t(nodetext, {key = node.key, node_callbacks = node.callbacks})
	else
		-- the above should be exhaustive, error if not.
		error("Cannot handle node!")
    end
end

This is pretty long, but only because textNode and functionNode require some special handling (isn needs an insert-position, but these nodes can't provide one, so we have to apply the indent without using isn, and IMO that works pretty well, but is verbose and a bit brittle because we have to extract the arguments the node was constructed with back out from the constructed object, which is not completely possible right now: ext_opts are changed quite a bit, so I've omitted them here)

But if we do this in fmt, we have all nodes of the node-list present, and know all their jump-indices, and can so prevent duplicates (presumably, but nothing prevents the caller from just adding more nodes, so that could be a bit brittle :|)