feat(#1826): allow using config from vim.diagnostic for icons + severity

doc/nvim-tree-lua.txt

@@ -1329,6 +1329,10 @@ Icons for diagnostic severity.
       error = ""
     }
 <
+*nvim-tree.diagnostics.diagnostic_opts*
+|vim.diagnostic.Opts| overrides |nvim-tree.diagnostics.severity| and
+|nvim-tree.diagnostics.icons|
+  Type: `boolean`, Default: `false`
 ==============================================================================
  5.9 OPTS: MODIFIED                                  *nvim-tree-opts-modified*
 

lua/nvim-tree.lua

@@ -420,6 +420,7 @@ local DEFAULT_OPTS = { -- BEGIN_DEFAULT_OPTS
       warning = "",
       error = "",
     },
+    diagnostic_opts = false,
   },
   modified = {
     enable = false,

lua/nvim-tree/diagnostics.lua

@@ -231,7 +231,10 @@ end
 function M.setup(opts)
   M.enable = opts.diagnostics.enable
   M.debounce_delay = opts.diagnostics.debounce_delay
-  M.severity = opts.diagnostics.severity
+  M.severity = opts.diagnostics.diagnostic_opts and {
+    min = vim.diagnostic.severity.HINT,
+    max = vim.diagnostic.severity.ERROR
+  } or opts.diagnostics.severity
 
   if M.enable then
     log.line("diagnostics", "setup")

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

@@ -41,17 +41,29 @@ local DiagnosticsDecorator = Decorator:extend()
 ---@protected
 ---@param args DecoratorArgs
 function DiagnosticsDecorator:new(args)
-  self.explorer        = args.explorer
+  self.explorer              = args.explorer
 
-  self.enabled         = true
-  self.highlight_range = self.explorer.opts.renderer.highlight_diagnostics or "none"
-  self.icon_placement  = self.explorer.opts.renderer.icons.diagnostics_placement or "none"
+  self.enabled               = true
+  self.highlight_range       = self.explorer.opts.renderer.highlight_diagnostics or "none"
+  self.icon_placement        = self.explorer.opts.renderer.icons.diagnostics_placement or "none"
+
+  local vim_diagnostic_icons = {}
+
+  if self.explorer.opts.diagnostics.diagnostic_opts then
+    local vim_diagnostic_config = vim.diagnostic.config() or {}
+    local signs                 = vim_diagnostic_config.signs or {}
+    if type(signs) == "function" then
+      signs = signs(0, 0)
+    end
+
+    vim_diagnostic_icons = (type(signs) == "table" and signs.text) or {}
+  end
 
   if self.explorer.opts.renderer.icons.show.diagnostics then
     self.diag_icons = {}
     for name, sev in pairs(ICON_KEYS) do
       self.diag_icons[sev] = {
-        str = self.explorer.opts.diagnostics.icons[name],
+        str = vim_diagnostic_icons[sev] or self.explorer.opts.diagnostics.icons[name],
         hl = { HG_ICON[sev] },
       }
       self:define_sign(self.diag_icons[sev])