REFACTOR: Updated from older config

lua/mason-conform/formatters.lua

@@ -0,0 +1,63 @@
+local M = {}
+
+---Collect formatter names from a single `formatters_by_ft` entry.
+---
+---A conform filetype formatter can be any of:
+---  * a list of formatter names, optionally followed by string-keyed format
+---    options (e.g. `{ "stylua", lsp_format = "fallback" }`)
+---  * a function `fun(bufnr): string[]`, used by the "run the first available
+---    formatter" recipe
+---  * the legacy nested list `{ { "prettierd", "prettier" } }`
+---
+---Only the array part of the table is traversed, so format options such as
+---`lsp_format` and `stop_after_first` are ignored.
+---@param value any
+---@param out table<string, boolean>
+local function collect_entry(value, out)
+    local list = value
+    if type(list) == "function" then
+        -- A function may depend on a buffer and/or on run-time availability.
+        -- We don't have a buffer to pass here, so evaluate it best-effort and
+        -- silently skip it when it cannot be called without one.
+        local ok, result = pcall(list)
+        if not ok or type(result) ~= "table" then
+            return
+        end
+        list = result
+    end
+
+    if type(list) ~= "table" then
+        return
+    end
+
+    for _, formatter in ipairs(list) do
+        if type(formatter) == "table" then
+            -- Legacy "run the first available formatter" syntax.
+            collect_entry(formatter, out)
+        elseif type(formatter) == "string" then
+            out[formatter] = true
+        end
+    end
+end
+
+---List every formatter configured in conform's `formatters_by_ft`.
+---
+---Understands all `formatters_by_ft` shapes supported by conform, including
+---functions returning a list and the legacy nested "run the first available"
+---syntax.
+---@return string[] names Sorted, de-duplicated formatter names.
+function M.configured()
+    local out = {}
+    for _, entry in pairs(require("conform").formatters_by_ft or {}) do
+        collect_entry(entry, out)
+    end
+
+    local names = {}
+    for name in pairs(out) do
+        names[#names + 1] = name
+    end
+    table.sort(names)
+    return names
+end
+
+return M