Filename evaluated *after* buffer is closed

[YodaEmbedding]

The filename() function is called once after the buffer is opened, and once after buffer is closed. This is problematic since the docs suggest:

local encoding = vim.api.nvim_buf_get_option(0, "fileencoding")

...but that's taking the encoding of the new buffer, not the one that was just closed!

Possible fixes:

1. Evaluate filename() only when the buffer is opened, then save this filename to an internal hash table that maps the buffer number/id to the filename. Also, update it if the user switches languages or encoding.
2. Just tell the user to always use "utf-8" since that's the most common encoding anyways.
3. Pass in an encoding argument into filename(). But the encoding should be determined before the file is closed.

  opts = {
    dictionary = {
      filename = function(lang, encoding)
        -- For example:
        -- lang = "en-US"
        -- lang_prefix = "en"
        -- encoding = "utf-8"
        -- filename = "en.utf-8.add"

        local lang_prefix = string.match(lang, "^(%a+)-")
        encoding = encoding or "utf-8"
        local filename = lang_prefix .. "." .. encoding .. ".add"

        return filename
    },
  },

Quick n' dirty patch:

diff --git a/lua/ltex-utils/words_cache.lua b/lua/ltex-utils/words_cache.lua
index 0f9ca28..3d8b920 100644
--- a/lua/ltex-utils/words_cache.lua
+++ b/lua/ltex-utils/words_cache.lua
@@ -53,8 +53,9 @@ function M:apply_cache(bufnr)
 
 	for lang, dict in pairs(dicts) do
 		---@type string
+		local encoding = vim.api.nvim_get_option_value("fileencoding", { buf = bufnr })
 		local filename = Config.dictionary.path ..
-											Config.dictionary.filename(lang)
+											Config.dictionary.filename(lang, encoding)
 		settings_io.write(
 			filename,
 			table.concat(dict, "\n") .. "\n",

[YodaEmbedding]

Also, a secondary issue:

function M.update_dictionary_files(dictionaries)
	for lang, dict in pairs(dictionaries) do
		M.write(filename, table.concat(dict, "\n") .. "\n")
	end
end

This leads to file corruption if filenames are identical for different langs. For instance, lang = en-US and lang = en-GB will both write to a file named en.utf-8.add.

To fix this:

diff --git a/lua/ltex-utils/settings_io.lua b/lua/ltex-utils/settings_io.lua
index cdbe4b6..ed8c45e 100644
--- a/lua/ltex-utils/settings_io.lua
+++ b/lua/ltex-utils/settings_io.lua
@@ -169,17 +169,21 @@ end
 function M.update_dictionary_files(dictionaries)
 	---@type string[]
 	local used_langs = {}
+	local used_filenames = {}
 	for lang, dict in pairs(dictionaries) do
 		---@type string
 		local filename = Config.dictionary.path ..
 											Config.dictionary.filename(lang)
-		---@type string[]|nil
-		local saved_dict = M.read_dictionary(filename)
-		-- if there is already a saved dictionary merge it with current one
-		if saved_dict then
-			dict = table_utils.merge_lists_unique(dict, saved_dict)
+		if not vim.tbl_contains(used_filenames, filename) then
+			---@type string[]|nil
+			local saved_dict = M.read_dictionary(filename)
+			-- if there is already a saved dictionary merge it with current one
+			if saved_dict then
+				dict = table_utils.merge_lists_unique(dict, saved_dict)
+			end
+			M.write(filename, table.concat(dict, "\n") .. "\n")
 		end
-		M.write(filename, table.concat(dict, "\n") .. "\n")
+		table.insert(used_filenames, filename)
 		table.insert(used_langs, lang)
 	end

Also, while we're at it, let's also write the output in a deterministic order for people (like me) who save their dictionaries in version control:

diff --git a/lua/ltex-utils/table_utils.lua b/lua/ltex-utils/table_utils.lua
index 168ab5d..d5f4455 100644
--- a/lua/ltex-utils/table_utils.lua
+++ b/lua/ltex-utils/table_utils.lua
@@ -49,6 +49,8 @@ function M.merge_lists_unique(list1, list2, changes)
 	---@type string[]
 	local merged_list = vim.tbl_keys(unique_elements)
 
+  table.sort(merged_list)
+
 	return merged_list
 end