1 files changed, 42 insertions, 12 deletions

diff --git a/runtime/lua/vim/lsp/diagnostic.lua b/runtime/lua/vim/lsp/diagnostic.lua
index b27bf6e425..dcc8f6549c 100644
--- a/runtime/lua/vim/lsp/diagnostic.lua
+++ b/runtime/lua/vim/lsp/diagnostic.lua
@@ -1,13 +1,6 @@
 ---@brief lsp-diagnostic
----
----@class Diagnostic
----@field range Range
----@field message string
----@field severity DiagnosticSeverity|nil
----@field code integer | string
----@field source string
----@field tags DiagnosticTag[]
----@field relatedInformation DiagnosticRelatedInformation[]
+
+local protocol = require('vim.lsp.protocol')
 
 local M = {}
 
@@ -22,14 +15,16 @@ local function get_client_id(client_id)
 end
 
 ---@private
+---@param severity lsp.DiagnosticSeverity
 local function severity_lsp_to_vim(severity)
   if type(severity) == 'string' then
-    severity = vim.lsp.protocol.DiagnosticSeverity[severity]
+    severity = protocol.DiagnosticSeverity[severity]
   end
   return severity
 end
 
 ---@private
+---@return lsp.DiagnosticSeverity
 local function severity_vim_to_lsp(severity)
   if type(severity) == 'string' then
     severity = vim.diagnostic.severity[severity]
@@ -38,6 +33,7 @@ local function severity_vim_to_lsp(severity)
 end
 
 ---@private
+---@return integer
 local function line_byte_from_position(lines, lnum, col, offset_encoding)
   if not lines or offset_encoding == 'utf-8' then
     return col
@@ -77,12 +73,41 @@ local function get_buf_lines(bufnr)
   return lines
 end
 
+--- @private
+--- @param diagnostic lsp.Diagnostic
+--- @param client_id integer
+--- @return table?
+local function tags_lsp_to_vim(diagnostic, client_id)
+  local tags ---@type table?
+  for _, tag in ipairs(diagnostic.tags or {}) do
+    if tag == protocol.DiagnosticTag.Unnecessary then
+      tags = tags or {}
+      tags.unnecessary = true
+    elseif tag == protocol.DiagnosticTag.Deprecated then
+      tags = tags or {}
+      tags.deprecated = true
+    else
+      vim.notify_once(
+        string.format('Unknown DiagnosticTag %d from LSP client %d', tag, client_id),
+        vim.log.levels.WARN
+      )
+    end
+  end
+  return tags
+end
+
 ---@private
+---@param diagnostics lsp.Diagnostic[]
+---@param bufnr integer
+---@param client_id integer
+---@return Diagnostic[]
 local function diagnostic_lsp_to_vim(diagnostics, bufnr, client_id)
   local buf_lines = get_buf_lines(bufnr)
   local client = vim.lsp.get_client_by_id(client_id)
   local offset_encoding = client and client.offset_encoding or 'utf-16'
+  ---@diagnostic disable-next-line:no-unknown
   return vim.tbl_map(function(diagnostic)
+    ---@cast diagnostic lsp.Diagnostic
     local start = diagnostic.range.start
     local _end = diagnostic.range['end']
     return {
@@ -94,12 +119,12 @@ local function diagnostic_lsp_to_vim(diagnostics, bufnr, client_id)
       message = diagnostic.message,
       source = diagnostic.source,
       code = diagnostic.code,
+      tags = tags_lsp_to_vim(diagnostic, client_id),
       user_data = {
         lsp = {
           -- usage of user_data.lsp.code is deprecated in favor of the top-level code field
           code = diagnostic.code,
           codeDescription = diagnostic.codeDescription,
-          tags = diagnostic.tags,
           relatedInformation = diagnostic.relatedInformation,
           data = diagnostic.data,
         },
@@ -108,9 +133,13 @@ local function diagnostic_lsp_to_vim(diagnostics, bufnr, client_id)
   end, diagnostics)
 end
 
----@private
+--- @private
+--- @param diagnostics Diagnostic[]
+--- @return lsp.Diagnostic[]
 local function diagnostic_vim_to_lsp(diagnostics)
+  ---@diagnostic disable-next-line:no-unknown
   return vim.tbl_map(function(diagnostic)
+    ---@cast diagnostic Diagnostic
     return vim.tbl_extend('keep', {
       -- "keep" the below fields over any duplicate fields in diagnostic.user_data.lsp
       range = {
@@ -131,6 +160,7 @@ local function diagnostic_vim_to_lsp(diagnostics)
   end, diagnostics)
 end
 
+---@type table<integer,integer>
 local _client_namespaces = {}
 
 --- Get the diagnostic namespace associated with an LSP client |vim.diagnostic|.