feat(fmt): enable indent string conversion

Author: xudyang1

lua/luasnip/extras/fmt.lua

@@ -185,12 +185,15 @@ end
 --   opts: optional table
 --     trim_empty: boolean, remove whitespace-only first/last lines, default true
 --     dedent: boolean, remove all common indent in `str`, default true
+--     indent_string: string, convert `indent_string` at beginning of each line to unit indent ('\t')
+--                            after applying `dedent`, default empty string (disabled)
 --     ... the rest is passed to `interpolate`
 -- Returns: list of snippet nodes
 local function format_nodes(str, nodes, opts)
 	local defaults = {
 		trim_empty = true,
 		dedent = true,
+		indent_string = "",
 	}
 	opts = vim.tbl_extend("force", defaults, opts or {})
 

lua/luasnip/util/str.lua

@@ -18,12 +18,46 @@ local function dedent(lines)
 	end
 end
 
+---Convert string `from` to unit indent
+---@param lines string[]
+---@param from string
+---@param unit_indent string
+local function convert_indent(lines, from, unit_indent)
+	local from_length = #from
+	if #lines == 0 or from_length == 0 or from == unit_indent then
+		return
+	end
+
+	local from_bytes = { string.byte(from, 1, from_length) }
+	for i = 1, #lines do
+		local line_bytes = { string.byte(lines[i], 1, #lines[i]) }
+		local line_length = #line_bytes
+		local indent_count = 0
+		local j, k = 1, 1
+		while j <= line_length and line_bytes[j] == from_bytes[k] do
+			if k == from_length then
+				indent_count = indent_count + 1
+			end
+			j = j + 1
+			k = k % from_length + 1
+		end
+		if indent_count > 0 then
+			lines[i] = string.format(
+				"%s%s",
+				string.rep(unit_indent, indent_count),
+				string.sub(lines[i], from_length * indent_count + 1)
+			)
+		end
+	end
+end
+
 ---Applies opts to lines.
 ---lines is modified in-place.
 ---@param lines string[].
 ---@param options table, required, can have values:
 ---  - trim_empty: removes empty first and last lines.
 ---  - dedent: removes indent common to all lines.
+---  - indent_string: an unit indent at beginning of each line after applying `dedent`, default empty string (disabled)
 function M.process_multiline(lines, options)
 	if options.trim_empty then
 		if lines[1]:match("^%s*$") then
@@ -37,6 +71,10 @@ function M.process_multiline(lines, options)
 	if options.dedent then
 		dedent(lines)
 	end
+
+	if options.indent_string and #options.indent_string > 0 then
+		convert_indent(lines, options.indent_string, "\t")
+	end
 end
 
 function M.dedent(s)
@@ -45,6 +83,12 @@ function M.dedent(s)
 	return table.concat(lst, "\n")
 end
 
+function M.convert_indent(s, indent_string)
+	local lst = vim.split(s, "\n")
+	convert_indent(lst, indent_string, "\t")
+	return table.concat(lst, "\n")
+end
+
 local function is_escaped(s, indx)
 	local count = 0
 	for i = indx - 1, 1, -1 do

tests/unit/str_spec.lua

@@ -60,3 +60,138 @@ describe("str.unescaped_pairs", function()
 		{ { 1, 3 }, { 5, 8 }, { 9, 11 } }
 	)
 end)
+
+describe("str.dedent", function()
+	-- apparently clear() needs to run before anything else...
+	ls_helpers.clear()
+	exec("set rtp+=" .. os.getenv("LUASNIP_SOURCE"))
+	local function get_dedent_result(input_string)
+		local result = exec_lua(
+			string.format(
+				[[return require("luasnip.util.str").dedent("%s")]],
+				input_string
+			)
+		)
+		return result
+	end
+
+	it("spaces at beginnig", function()
+		local input_table = {
+			"  line1",
+			"  ",
+			"    line3",
+			"      line4",
+		}
+		local input_string = table.concat(input_table, [[\n]])
+		local expect_table = {
+			"line1",
+			"",
+			"  line3",
+			"    line4",
+		}
+		local expected = table.concat(expect_table, "\n")
+
+		local result = get_dedent_result(input_string)
+
+		assert.are.same(expected, result)
+	end)
+	it("tabs at beginnig", function()
+		local input_table = {
+			[[\t\tline1]],
+			[[\t\t]],
+			[[\t\t\tline3]],
+			[[\t\t\t\tline4]],
+		}
+		local input_string = table.concat(input_table, [[\n]])
+		local expect_table = {
+			"line1",
+			"",
+			"\tline3",
+			"\t\tline4",
+		}
+		local expected = table.concat(expect_table, "\n")
+
+		local result = get_dedent_result(input_string)
+
+		assert.are.same(expected, result)
+	end)
+	it("tabs & spaces at beginnig", function()
+		local input_table = {
+			[[\t\t line1]],
+			[[\t\t ]],
+			[[\t\t \t  line3]],
+			[[\t\t \t\t  line4]],
+		}
+		local input_string = table.concat(input_table, [[\n]])
+		local expect_table = {
+			"line1",
+			"",
+			"\t  line3",
+			"\t\t  line4",
+		}
+		local expected = table.concat(expect_table, "\n")
+
+		local result = get_dedent_result(input_string)
+
+		assert.are.same(expected, result)
+	end)
+end)
+
+describe("str.convert_indent", function()
+	-- apparently clear() needs to run before anything else...
+	ls_helpers.clear()
+	exec("set rtp+=" .. os.getenv("LUASNIP_SOURCE"))
+	local function get_convert_indent_result(input_string, indent_string)
+		local result = exec_lua(
+			string.format(
+				[[return require("luasnip.util.str").convert_indent("%s", "%s")]],
+				input_string,
+				indent_string
+			)
+		)
+		return result
+	end
+
+	it("two spaces to tab", function()
+		local input_table = {
+			"line1: no indent",
+			"",
+			"  line3: 1 indent",
+			"    line4: 2 indent",
+		}
+		local input_string = table.concat(input_table, [[\n]])
+		local indent_string = "  "
+		local expect_table = {
+			"line1: no indent",
+			"",
+			"\tline3: 1 indent",
+			"\t\tline4: 2 indent",
+		}
+		local expected = table.concat(expect_table, "\n")
+
+		local result = get_convert_indent_result(input_string, indent_string)
+
+		assert.are.same(expected, result)
+	end)
+	it([[literal \t to tab]], function()
+		local input_table = {
+			"line1: no indent",
+			"",
+			[[\\tline3: 1 indent]],
+			[[\\t\\tline4: 2 indent]],
+		}
+		local input_string = table.concat(input_table, [[\n]])
+		local indent_string = [[\\t]]
+		local expect_table = {
+			"line1: no indent",
+			"",
+			"\tline3: 1 indent",
+			"\t\tline4: 2 indent",
+		}
+		local expected = table.concat(expect_table, "\n")
+
+		local result = get_convert_indent_result(input_string, indent_string)
+
+		assert.are.same(expected, result)
+	end)
+end)