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-- Snippet engine. Owns the always-on machinery (expansion fallback, the completion source, the
-- placeholder-jump keymaps) and turns snippets on per filetype: `add(ft, definitions)` registers a
-- FileType autocmd that exposes the definitions to the completion source. Definitions live in
-- plugin/50-snippet.lua.
--
-- API:
-- add(filetype, definitions) — enable `definitions` (trigger word -> LSP snippet body) for
-- `filetype` (a string or list of filetypes)
local M = {}
----------------------------------------------------------------------------------------------------
-- Snippet expansion fallback
----------------------------------------------------------------------------------------------------
-- Work around Neovim's snippet grammar rejecting placeholder defaults that mix text with nested
-- tabstops (e.g. lua_ls's `${1:pairs(${2:t})}`): the `any_or_text` rule matches a single node, not
-- a `(any + text)^1` sequence. On parse failure, strip the snippet markup and insert it as plain
-- text instead of throwing. Remove once fixed upstream.
-- The `@as table` cast retypes the module here so overriding `expand` isn't flagged as a duplicate
-- field set.
local snippet = vim.snippet --[[@as table]]
local orig_expand = snippet.expand
-- Reduce LSP snippet syntax to plain text: keep placeholder/variable defaults, the first choice,
-- drop bare tabstops.
local function strip_snippet(s)
local prev
repeat
prev = s
s = s:gsub("%$(%b{})", function(group)
local body = group:sub(2, -2)
local choice = body:match("^%d+|(.*)|$")
if choice then
return (choice:gsub(",.*$", "")) -- first choice
end
local default = body:match("^[%w_]+:(.*)$")
if default then
return default -- ${n:default} / ${VAR:default}
end
return "" -- bare ${n} / ${VAR}
end)
until s == prev
s = s:gsub("%$[%w_]+", "") -- bare $n / $VAR
s = s:gsub("\\([%$}{|,\\])", "%1") -- unescape
return s
end
-- Insert `text` at the cursor as literal lines, re-indenting continuation lines to the current
-- indent, and leave the cursor at the end of the inserted text.
local function insert_plain(text)
local win = vim.api.nvim_get_current_win()
local row, col = unpack(vim.api.nvim_win_get_cursor(win))
local indent = vim.api.nvim_get_current_line():match("^%s*") or ""
local lines = vim.split(text, "\n", { plain = true })
for i = 2, #lines do
lines[i] = indent .. lines[i]
end
vim.api.nvim_buf_set_text(0, row - 1, col, row - 1, col, lines)
local last = #lines
local new_row = row - 1 + (last - 1)
local new_col = last == 1 and col + #lines[1] or #lines[last]
vim.api.nvim_win_set_cursor(win, { new_row + 1, new_col })
end
-- Expand normally; on a parse failure fall back to inserting the stripped snippet as plain text.
snippet.expand = function(input)
local ok = pcall(orig_expand, input)
if not ok then
insert_plain(strip_snippet(input))
vim.notify(
"Snippet parse failed, inserted as plain text: " .. vim.inspect(input),
vim.log.levels.WARN
)
end
end
----------------------------------------------------------------------------------------------------
-- Completion source
----------------------------------------------------------------------------------------------------
-- Exposes `vim.b.snippets` (trigger word -> LSP snippet body) as a 'complete' function source. A
-- filetype opts in through `add()` below, which sets `vim.b.snippets`, points 'completefunc' here,
-- and appends "F" to 'complete'. `dotfiles_snippet_source` must be a global so `v:lua` can reach
-- it; see `:help complete-functions` and `:help v:lua-call`.
-- Render a snippet to preview text: resolve placeholders and their mirrors to the placeholder's
-- default value.
local function render_snippet(s)
local defaults = {}
for n, d in s:gmatch("%${(%d+):([^{}]*)}") do
defaults[n] = d
end
local prev
repeat
prev = s
s = s:gsub("%$(%b{})", function(group)
local body = group:sub(2, -2)
local choice = body:match("^%d+|(.*)|$")
if choice then
return (choice:gsub(",.*$", "")) -- first choice
end
local default = body:match("^[%w_]+:(.*)$")
if default then
return default -- ${n:default} / ${VAR:default}
end
return defaults[body] or "" -- ${n} / ${VAR}
end)
until s == prev
s = s:gsub("%$(%d+)", function(n)
return defaults[n] or "" -- $n mirror
end)
s = s:gsub("%$[%w_]+", "") -- bare $VAR
s = s:gsub("\\([%$}{|,\\])", "%1") -- unescape
return s
end
-- 'completefunc' source: report the replaced range on the first pass, then the matching snippet
-- triggers (with rendered preview and the body stashed in user_data for CompleteDone).
function _G.dotfiles_snippet_source(findstart, base)
local snippets = vim.b.snippets or {}
local line = vim.api.nvim_get_current_line()
local col = vim.api.nvim_win_get_cursor(0)[2]
if findstart == 1 then
-- Walk back over trigger characters to find the range the match replaces.
local start = col
while start > 0 and line:sub(start, start):match("[%w_]") do
start = start - 1
end
return start
end
local items = {}
for trigger, body in pairs(snippets) do
if vim.startswith(trigger, base) then
items[#items + 1] = {
word = trigger,
kind = "Snippet",
menu = "[snippet]",
info = render_snippet(body),
user_data = { snippet = body },
}
end
end
return items
end
-- Expand the snippet once one of the items above is accepted (its trigger word is inserted first,
-- so remove it).
vim.api.nvim_create_autocmd("CompleteDone", {
desc = "Expand accepted snippet completion",
group = vim.g.dotfiles.augroup,
callback = function()
local item = vim.v.completed_item
local data = item.user_data
if type(data) ~= "table" or not data.snippet then
return
end
local row, col = unpack(vim.api.nvim_win_get_cursor(0))
vim.api.nvim_buf_set_text(0, row - 1, col - #item.word, row - 1, col, { "" })
vim.snippet.expand(data.snippet)
end,
})
----------------------------------------------------------------------------------------------------
-- Placeholder jumping
----------------------------------------------------------------------------------------------------
-- Jump between snippet placeholders, falling back to native behavior when no snippet is active.
vim.keymap.set({ "i", "s" }, "<C-n>", function()
return vim.snippet.active({ direction = 1 }) and "<Cmd>lua vim.snippet.jump(1)<CR>" or "<C-n>"
end, { expr = true })
vim.keymap.set({ "i", "s" }, "<C-p>", function()
return vim.snippet.active({ direction = -1 }) and "<Cmd>lua vim.snippet.jump(-1)<CR>" or "<C-p>"
end, { expr = true })
----------------------------------------------------------------------------------------------------
-- Registration
----------------------------------------------------------------------------------------------------
-- Enable `definitions` for `filetype` (a string or list): on FileType, stash them in
-- `vim.b.snippets`, point 'completefunc' at the source, and add "F" to 'complete' so they surface
-- in the completion menu.
function M.add(filetype, definitions)
vim.api.nvim_create_autocmd("FileType", {
desc = "Enable snippets",
group = vim.g.dotfiles.augroup,
pattern = filetype,
callback = function()
vim.b.snippets = definitions
vim.bo.completefunc = "v:lua.dotfiles_snippet_source"
vim.opt_local.complete:append("F")
end,
})
end
return M
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