Make :TSInstall work in Nix by adding a second module installation target (#473)

* Ignore tags file in project root

* Make :TSInstall work with Nix

This commit adds logic to determine where to install parsers, meaning
the *.so files. Until now the package path of the nvim-treesitter plugin
was used. But when installed with Nix, the plugin lands in "/nix/store",
which is read-only.

With this commit $XDG_DATA_HOME/nvim/site/parser/*.go will be used as
the parser installation path. The directory will be created if it
doesn't exist.

* Add generate_join function

The generate_join function is used to create two other functions, one
to join path segments, the other to join strings with a space for error
messages.

1 files changed, 13 insertions, 12 deletions

diff --git a/lua/nvim-treesitter/install.lua b/lua/nvim-treesitter/install.lua
index 0d2d7481..4c52fd41 100644
--- a/lua/nvim-treesitter/install.lua
+++ b/lua/nvim-treesitter/install.lua
@@ -117,18 +117,15 @@ local function select_mv_cmd(compile_location, parser_lib_name)
   end
 end
 
-local function run_install(cache_folder, package_path, lang, repo, with_sync)
+local function run_install(cache_folder, install_folder, lang, repo, with_sync)
   parsers.reset_cache()
 
-  local path_sep = '/'
-  if fn.has('win32') == 1 then
-    path_sep = '\\'
-  end
+  local path_sep = utils.get_path_sep()
 
   local project_name = 'tree-sitter-'..lang
   -- compile_location only needed for typescript installs.
   local compile_location = cache_folder..path_sep..(repo.location or project_name)
-  local parser_lib_name = package_path..path_sep.."parser"..path_sep..lang..".so"
+  local parser_lib_name = install_folder..path_sep..lang..".so"
 
   local compilers = { "cc", "gcc", "clang" }
   local cc = select_executable(compilers)
@@ -170,7 +167,7 @@ local function run_install(cache_folder, package_path, lang, repo, with_sync)
   end
 end
 
-local function install_lang(lang, ask_reinstall, cache_folder, package_path, with_sync)
+local function install_lang(lang, ask_reinstall, cache_folder, install_folder, with_sync)
   if #api.nvim_get_runtime_file('parser/'..lang..'.so', false) > 0 then
     if ask_reinstall ~= 'force' then
       if not ask_reinstall then return end
@@ -192,7 +189,7 @@ local function install_lang(lang, ask_reinstall, cache_folder, package_path, wit
     files={ install_info.files, 'table' }
   }
 
-  run_install(cache_folder, package_path, lang, install_info, with_sync)
+  run_install(cache_folder, install_folder, lang, install_info, with_sync)
 end
 
 local function install(with_sync, ask_reinstall)
@@ -202,10 +199,12 @@ local function install(with_sync, ask_reinstall)
       return api.nvim_err_writeln('Git is required on your system to run this command')
     end
 
-    local package_path = utils.get_package_path()
     local cache_folder, err = utils.get_cache_dir()
     if err then return api.nvim_err_writeln(err) end
 
+    local install_folder, err = utils.get_parser_install_dir()
+    if err then return api.nvim_err_writeln(err) end
+
     local languages
     local ask
     if ... == 'all' then
@@ -217,7 +216,7 @@ local function install(with_sync, ask_reinstall)
     end
 
     for _, lang in ipairs(languages) do
-      install_lang(lang, ask, cache_folder, package_path, with_sync)
+      install_lang(lang, ask, cache_folder, install_folder, with_sync)
     end
   end
 end
@@ -267,8 +266,10 @@ function M.uninstall(lang)
       M.uninstall(lang)
     end
   elseif lang then
-    local package_path = utils.get_package_path()
-    local parser_lib = package_path..path_sep.."parser"..path_sep..lang..".so"
+    local install_dir, err = utils.get_parser_install_dir()
+    if err then return api.nvim_err_writeln(err) end
+
+    local parser_lib = install_dir..path_sep..lang..".so"
 
     local command_list = {
       select_uninstall_rm_cmd(lang, parser_lib)