fix(lsp): check if buffer was detached in on_init callback (#28914)

Co-authored-by: Jongwook Choi <wookayin@gmail.com>

5 files changed, 71 insertions, 40 deletions

diff --git a/runtime/lua/vim/lsp/client.lua b/runtime/lua/vim/lsp/client.lua
index 8fb5879e9b..4beb7fefda 100644
--- a/runtime/lua/vim/lsp/client.lua
+++ b/runtime/lua/vim/lsp/client.lua
@@ -612,7 +612,10 @@ function Client:initialize()
     self:_run_callbacks(self._on_init_cbs, lsp.client_errors.ON_INIT_CALLBACK_ERROR, self, result)
 
     for buf in pairs(reattach_bufs) do
-      self:_on_attach(buf)
+      -- The buffer may have been detached in the on_init callback.
+      if self.attached_buffers[buf] then
+        self:_on_attach(buf)
+      end
     end
 
     log.info(
diff --git a/test/functional/plugin/lsp/inlay_hint_spec.lua b/test/functional/plugin/lsp/inlay_hint_spec.lua
index 3d0fcc31ff..d3b5ae0e4e 100644
--- a/test/functional/plugin/lsp/inlay_hint_spec.lua
+++ b/test/functional/plugin/lsp/inlay_hint_spec.lua
@@ -70,8 +70,8 @@ before_each(function()
         inlayHintProvider = true,
       },
       handlers = {
-        ['textDocument/inlayHint'] = function()
-          return vim.json.decode(response)
+        ['textDocument/inlayHint'] = function(_, _, callback)
+          callback(nil, vim.json.decode(response))
         end,
       }
     })
@@ -106,8 +106,8 @@ describe('vim.lsp.inlay_hint', function()
           inlayHintProvider = true,
         },
         handlers = {
-          ['textDocument/inlayHint'] = function()
-            return {}
+          ['textDocument/inlayHint'] = function(_, _, callback)
+            callback(nil, {})
           end,
         }
       })
@@ -206,8 +206,8 @@ describe('vim.lsp.inlay_hint', function()
             inlayHintProvider = true,
           },
           handlers = {
-            ['textDocument/inlayHint'] = function()
-              return { expected2 }
+            ['textDocument/inlayHint'] = function(_, _, callback)
+              callback(nil, { expected2 })
             end,
           }
         })
diff --git a/test/functional/plugin/lsp/semantic_tokens_spec.lua b/test/functional/plugin/lsp/semantic_tokens_spec.lua
index 60f02b0521..7908c5d2e7 100644
--- a/test/functional/plugin/lsp/semantic_tokens_spec.lua
+++ b/test/functional/plugin/lsp/semantic_tokens_spec.lua
@@ -95,11 +95,11 @@ describe('semantic token highlighting', function()
             },
           },
           handlers = {
-            ['textDocument/semanticTokens/full'] = function()
-              return vim.fn.json_decode(response)
+            ['textDocument/semanticTokens/full'] = function(_, _, callback)
+              callback(nil, vim.fn.json_decode(response))
             end,
-            ['textDocument/semanticTokens/full/delta'] = function()
-              return vim.fn.json_decode(edit_response)
+            ['textDocument/semanticTokens/full/delta'] = function(_, _, callback)
+              callback(nil, vim.fn.json_decode(edit_response))
             end,
           }
         })
@@ -560,11 +560,11 @@ describe('semantic token highlighting', function()
             },
           },
           handlers = {
-            ['textDocument/semanticTokens/full'] = function()
-              return nil
+            ['textDocument/semanticTokens/full'] = function(_, _, callback)
+              callback(nil, nil)
             end,
             ['textDocument/semanticTokens/full/delta'] = function()
-              return nil
+              callback(nil, nil)
             end,
           }
         })
@@ -608,11 +608,11 @@ describe('semantic token highlighting', function()
             },
           },
           handlers = {
-            ['textDocument/semanticTokens/full'] = function()
-              return vim.fn.json_decode(response)
+            ['textDocument/semanticTokens/full'] = function(_, _, callback)
+              callback(nil, vim.fn.json_decode(response))
             end,
-            ['textDocument/semanticTokens/full/delta'] = function()
-              return vim.fn.json_decode(edit_response)
+            ['textDocument/semanticTokens/full/delta'] = function(_, _, callback)
+              callback(nil, vim.fn.json_decode(edit_response))
             end,
           }
         })
@@ -1075,8 +1075,8 @@ b = "as"]],
               },
             },
             handlers = {
-              ['textDocument/semanticTokens/full'] = function()
-                return vim.fn.json_decode(resp)
+              ['textDocument/semanticTokens/full'] = function(_, _, callback)
+                callback(nil, vim.fn.json_decode(resp))
               end,
             }
           })
@@ -1461,11 +1461,11 @@ int main()
               },
             },
             handlers = {
-              ['textDocument/semanticTokens/full'] = function()
-                return vim.fn.json_decode(resp1)
+              ['textDocument/semanticTokens/full'] = function(_, _, callback)
+                callback(nil, vim.fn.json_decode(resp1))
               end,
-              ['textDocument/semanticTokens/full/delta'] = function()
-                return vim.fn.json_decode(resp2)
+              ['textDocument/semanticTokens/full/delta'] = function(_, _, callback)
+                callback(nil, vim.fn.json_decode(resp2))
               end,
             }
           })
diff --git a/test/functional/plugin/lsp/testutil.lua b/test/functional/plugin/lsp/testutil.lua
index 4d14752f2a..3430a1e1a3 100644
--- a/test/functional/plugin/lsp/testutil.lua
+++ b/test/functional/plugin/lsp/testutil.lua
@@ -39,8 +39,7 @@ M.create_server_definition = [[
         })
         local handler = handlers[method]
         if handler then
-          local response, err = handler(method, params)
-          callback(err, response)
+          handler(method, params, callback)
         elseif method == 'initialize' then
           callback(nil, {
             capabilities = opts.capabilities or {}
diff --git a/test/functional/plugin/lsp_spec.lua b/test/functional/plugin/lsp_spec.lua
index 8358a1b9ec..c95a96baca 100644
--- a/test/functional/plugin/lsp_spec.lua
+++ b/test/functional/plugin/lsp_spec.lua
@@ -501,6 +501,35 @@ describe('LSP', function()
       eq(true, result.detach_called)
     end)
 
+    it('should not re-attach buffer if it was deleted in on_init #28575', function()
+      clear()
+      exec_lua(create_server_definition)
+      exec_lua([[
+        local server = _create_server({
+          handlers = {
+            initialize = function(method, params, callback)
+              vim.schedule(function()
+                callback(nil, { capabilities = {} })
+              end)
+            end
+          }
+        })
+        local bufnr = vim.api.nvim_create_buf(false, true)
+        local on_init_called = false
+        local client_id = vim.lsp.start({
+          name = 'detach-dummy',
+          cmd = server.cmd,
+          on_init = function()
+            vim.api.nvim_buf_delete(bufnr, {})
+            on_init_called = true
+          end
+        })
+        vim.lsp.buf_attach_client(bufnr, client_id)
+        local ok = vim.wait(1000, function() return on_init_called end)
+        assert(ok, "on_init was not called")
+      ]])
+    end)
+
     it('client should return settings via workspace/configuration handler', function()
       local expected_handlers = {
         { NIL, {}, { method = 'shutdown', client_id = 1 } },
@@ -670,7 +699,7 @@ describe('LSP', function()
             }
           },
           handlers = {
-            ['textDocument/willSaveWaitUntil'] = function()
+            ['textDocument/willSaveWaitUntil'] = function(_, _, callback)
               local text_edit = {
                 range = {
                   start = { line = 0, character = 0 },
@@ -678,7 +707,7 @@ describe('LSP', function()
                 },
                 newText = 'Hello'
               }
-              return { text_edit, }
+              callback(nil, { text_edit, })
             end
           },
         })
@@ -4144,8 +4173,8 @@ describe('LSP', function()
             }
           },
           handlers = {
-            ["textDocument/codeAction"] = function()
-              return {
+            ["textDocument/codeAction"] = function(_, _, callback)
+              callback(nil, {
                 {
                   title = "Code Action 1",
                   command = {
@@ -4153,10 +4182,10 @@ describe('LSP', function()
                     command = "command:1",
                   }
                 }
-              }
+              })
             end,
-            ["codeAction/resolve"] = function()
-              return nil, "resolve failed"
+            ["codeAction/resolve"] = function(_, _, callback)
+              callback("resolve failed", nil)
             end,
           }
         })
@@ -4344,7 +4373,7 @@ describe('LSP', function()
               },
             },
             handlers = {
-              ["textDocument/codeLens"] = function(method, params)
+              ["textDocument/codeLens"] = function(method, params, callback)
                 local lenses = {
                   {
                     range = {
@@ -4357,7 +4386,7 @@ describe('LSP', function()
                     },
                   },
                 }
-                return lenses
+                callback(nil, lenses)
               end,
             }
           })
@@ -4665,13 +4694,13 @@ describe('LSP', function()
           },
           handlers = {
             ---@return lsp.Location[]
-            ['textDocument/definition'] = function()
-              return { _G.mock_locations[1] }
+            ['textDocument/definition'] = function(_, _, callback)
+              callback(nil, { _G.mock_locations[1] })
             end,
             ---@return lsp.WorkspaceSymbol[]
-            ['workspace/symbol'] = function(_, request)
+            ['workspace/symbol'] = function(_, request, callback)
               assert(request.query == 'foobar')
-              return {
+              callback(nil, {
                 {
                   name = 'foobar',
                   kind = 13, ---@type lsp.SymbolKind
@@ -4682,7 +4711,7 @@ describe('LSP', function()
                   kind = 12, ---@type lsp.SymbolKind
                   location = _G.mock_locations[2],
                 }
-              }
+              })
             end,
           },
         })