feat(#1826): use diagnostics icons from vim.diagnostic

Author: igorlfs

lua/nvim-tree/renderer/decorator/diagnostics.lua

@@ -3,6 +3,17 @@ local diagnostics = require("nvim-tree.diagnostics")
 local Decorator = require("nvim-tree.renderer.decorator")
 local DirectoryNode = require("nvim-tree.node.directory")
 
+---@param severity vim.diagnostic.Severity
+---@return string?
+local function get_diagnostics_icons(severity)
+  local config = vim.diagnostic.config() or {}
+  local signs = config.signs or {}
+  if type(signs) == "function" then
+    signs = signs(0, 0)
+  end
+  return (type(signs) == "table" and signs.text and signs.text[severity]) or nil
+end
+
 -- highlight groups by severity
 local HG_ICON = {
   [vim.diagnostic.severity.ERROR] = "NvimTreeDiagnosticErrorIcon",
@@ -51,7 +62,7 @@ function DiagnosticsDecorator:new(args)
     self.diag_icons = {}
     for name, sev in pairs(ICON_KEYS) do
       self.diag_icons[sev] = {
-        str = self.explorer.opts.diagnostics.icons[name],
+        str = get_diagnostics_icons(sev) or self.explorer.opts.diagnostics.icons[name],
         hl = { HG_ICON[sev] },
       }
       self:define_sign(self.diag_icons[sev])