From 76486942e79973095795e8699f95bb509e063d0d Mon Sep 17 00:00:00 2001
From: Luis Carlos Cruz Carballo <lcruzc@linkux-it.com>
Date: Mon, 30 Nov 2020 21:30:07 -0400
Subject: Allow user configure parsers using metatables

---
 README.md                       | 13 +++++++++++++
 lua/nvim-treesitter/parsers.lua | 39 +++++++++++++++++++++++++++------------
 2 files changed, 40 insertions(+), 12 deletions(-)

diff --git a/README.md b/README.md
index 03466ba0..ba3b45a7 100644
--- a/README.md
+++ b/README.md
@@ -275,6 +275,19 @@ EOF
 You can also skip step 2 and use `:TSInstallFromGrammar zimbu` to install directly from a `grammar.js` in the top-level directory specified by `url`.
 Once the parser is installed, you can update it (from the latest revision of the `main` branch if `url` is a Github repository) with `:TSUpdate zimbu`.
 
+## Update parsers used_by
+
+Sometimes needs to use some parser for different filetype.
+
+Add the following snippet to your `init.vim`:
+
+```vim
+lua <<EOF
+local parser_config = require "nvim-treesitter.parsers".get_parser_configs()
+parser_config.typescript.used_by = "javascriptflow"
+EOF
+```
+
 ## Adding queries
 
 Queries are what `nvim-treesitter` uses to extract informations from the syntax tree; they are
diff --git a/lua/nvim-treesitter/parsers.lua b/lua/nvim-treesitter/parsers.lua
index e43d2ff0..7b10f1ca 100644
--- a/lua/nvim-treesitter/parsers.lua
+++ b/lua/nvim-treesitter/parsers.lua
@@ -1,7 +1,33 @@
 local api = vim.api
 local ts = vim.treesitter
 
-local list = {}
+local ft_to_parsername = {}
+
+local function update_ft_to_parsername(name, parser)
+  if type(parser.used_by) == 'table' then
+    for _, ft in pairs(parser.used_by) do
+      ft_to_parsername[ft] = name
+    end
+  end
+  ft_to_parsername[parser.filetype or name] = name
+end
+
+local list = setmetatable({}, {
+  __newindex = function(table, parsername, parserconfig)
+
+    rawset(table, parsername, setmetatable(parserconfig, {
+      __newindex = function(parserconfigtable, key, value)
+        if key == "used_by" then
+          ft_to_parsername[value] = parsername
+        else
+          rawset(parserconfigtable, key, value)
+        end
+      end
+    }))
+
+    update_ft_to_parsername(parsername, parserconfig)
+   end
+})
 
 list.javascript = {
   install_info = {
@@ -349,17 +375,6 @@ local M = {
   list = list
 }
 
-local ft_to_parsername = {}
-
-for name, obj in pairs(M.list) do
-  if type(obj.used_by) == 'table' then
-    for _, ft in pairs(obj.used_by) do
-      ft_to_parsername[ft] = name
-    end
-  end
-  ft_to_parsername[obj.filetype or name] = name
-end
-
 function M.ft_to_lang(ft)
   return ft_to_parsername[ft] or ft
 end
-- 
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