fix(lsp): show notification with empty hover response (#35014)

runtime/lua/vim/lsp/buf.lua

@@ -61,20 +61,33 @@ function M.hover(config)
 
     -- Filter errors from results
     local results1 = {} --- @type table<integer,lsp.Hover>
+    local empty_response = false
 
     for client_id, resp in pairs(results) do
       local err, result = resp.err, resp.result
       if err then
         lsp.log.error(err.code, err.message)
-      elseif result then
+      elseif result and result.contents then
+        -- Make sure the response is not empty
+        if
+          (type(result.contents) == 'table' and #(vim.tbl_get(result.contents, 'value') or '') > 0)
+          or type(result.contents == 'string') and #result.contents > 0
+        then
           results1[client_id] = result
+        else
+          empty_response = true
+        end
       end
     end
 
     if vim.tbl_isempty(results1) then
       if config.silent ~= true then
+        if empty_response then
+          vim.notify('Empty hover response', vim.log.levels.INFO)
+        else
           vim.notify('No information available', vim.log.levels.INFO)
         end
+      end
       return
     end
 

test/functional/plugin/lsp_spec.lua

@@ -7110,4 +7110,31 @@ describe('LSP', function()
       )
     end)
   end)
+
+  describe('vim.lsp.buf.hover()', function()
+    it('handles empty contents', function()
+      exec_lua(create_server_definition)
+      exec_lua(function()
+        local server = _G._create_server({
+          capabilities = {
+            hoverProvider = true,
+          },
+          handlers = {
+            ['textDocument/hover'] = function(_, _, callback)
+              local res = {
+                contents = {
+                  kind = 'markdown',
+                  value = '',
+                },
+              }
+              callback(nil, res)
+            end,
+          },
+        })
+        vim.lsp.start({ name = 'dummy', cmd = server.cmd })
+      end)
+
+      eq('Empty hover response', n.exec_capture('lua vim.lsp.buf.hover()'))
+    end)
+  end)
 end)