feat(lsp): support dynamic registration for diagnostics (#36841)

runtime/doc/news.txt

@@ -284,6 +284,7 @@ LSP
 • |Client:stop()| now uses the `Client.exit_timeout` field to control the default of `force`.
 • Support for `workspace/diagnostic/refresh`:
   https://microsoft.github.io/language-server-protocol/specification/#diagnostic_refresh
+- Support for dynamic registration for `textDocument/diagnostic`
 
 LUA
 

runtime/lua/vim/lsp/diagnostic.lua

@@ -358,7 +358,7 @@ end
 ---@param bufnr integer buffer number
 ---@param client_id? integer Client ID to refresh (default: all clients)
 ---@param only_visible? boolean Whether to only refresh for the visible regions of the buffer (default: false)
-local function refresh(bufnr, client_id, only_visible)
+function M._refresh(bufnr, client_id, only_visible)
   if
     only_visible
     and vim.iter(api.nvim_list_wins()):all(function(window)
@@ -407,7 +407,7 @@ function M.on_refresh(err, _, ctx)
   else
     for bufnr in pairs(client.attached_buffers or {}) do
       if bufstates[bufnr] and bufstates[bufnr].pull_kind == 'document' then
-        refresh(bufnr)
+        M._refresh(bufnr)
       end
     end
   end
@@ -442,7 +442,7 @@ function M._enable(bufnr)
       end
       if bufstates[bufnr] and bufstates[bufnr].pull_kind == 'document' then
         local client_id = opts.data.client_id --- @type integer?
-        refresh(bufnr, client_id, true)
+        M._refresh(bufnr, client_id, true)
       end
     end,
     group = augroup,
@@ -451,7 +451,7 @@ function M._enable(bufnr)
   api.nvim_buf_attach(bufnr, false, {
     on_reload = function()
       if bufstates[bufnr] and bufstates[bufnr].pull_kind == 'document' then
-        refresh(bufnr)
+        M._refresh(bufnr)
       end
     end,
     on_detach = function()

runtime/lua/vim/lsp/handlers.lua

@@ -158,6 +158,11 @@ RSC['client/registerCapability'] = function(_, params, ctx)
         end
       end
     end
+    if reg.method == 'textDocument/diagnostic' then
+      for bufnr in pairs(client.attached_buffers) do
+        vim.lsp.diagnostic._refresh(bufnr, client.id)
+      end
+    end
   end
   return vim.NIL
 end

runtime/lua/vim/lsp/protocol.lua

@@ -352,7 +352,7 @@ function protocol.make_client_capabilities()
     },
     textDocument = {
       diagnostic = {
-        dynamicRegistration = false,
+        dynamicRegistration = true,
         tagSupport = {
           valueSet = get_value_set(constants.DiagnosticTag),
         },

test/functional/plugin/lsp/diagnostic_spec.lua

@@ -498,6 +498,42 @@ describe('vim.lsp.diagnostic', function()
       )
     end)
 
+    it('supports dynamic registration', function()
+      exec_lua(create_server_definition)
+      exec_lua(function()
+        _G.server2 = _G._create_server({
+          diagnosticProvider = {
+            documentSelector = vim.NIL,
+          },
+          handlers = {
+            ['textDocument/diagnostic'] = function(_, _, callback)
+              callback(nil, {
+                kind = 'full',
+                items = {
+                  _G.make_error('Dynamic Diagnostic', 4, 4, 4, 4),
+                },
+              })
+            end,
+          },
+        })
+
+        local client_id2 = assert(vim.lsp.start({ name = 'dummy2', cmd = _G.server2.cmd }))
+
+        vim.lsp.handlers['client/registerCapability'](nil, {
+          registrations = {
+            { id = 'diagnostic', method = 'textDocument/diagnostic' },
+          },
+        }, { client_id = client_id2, method = 'client/registerCapability' })
+      end)
+
+      eq(
+        1,
+        exec_lua(function()
+          return #vim.diagnostic.get(diagnostic_bufnr)
+        end)
+      )
+    end)
+
     it('requests with the `previousResultId`', function()
       -- Full reports
       eq(