fix(lsp): Fix LSP server attachment and JSON parsing issues

- Replace lspconfig.scl_lsp registration with vim.lsp.start() + FileType autocmd
  for Neovim 0.11+ compatibility
- Fix Lua reserved keyword 'end' in tables (use bracket notation ['end'])
- Fix JSON decoder pattern matching bugs (s:find -> s:sub:match)
- Add LSP method name conversion (textDocument/didOpen -> textDocument_didOpen)
- Handle request vs notification correctly (only respond to requests with id)
- Strip CRLF line endings for Windows compatibility
- Add semantic token handler aliases
- Update documentation with implementation notes

AGENTS.md

@@ -104,6 +104,19 @@ function M.clear_cache()
 end
 ```
 
+## Lua Reserved Keywords
+
+Lua reserved keywords (like `end`, `for`, `in`, etc.) cannot be used as table keys directly. Use bracket notation:
+```lua
+-- WRONG: causes syntax error
+local range = { start = pos1, end = pos2 }
+
+-- CORRECT: use bracket notation
+local range = { start = pos1, ["end"] = pos2 }
+```
+
+This is especially important for LSP range objects which require an `end` field per the LSP specification.
+
 ## Error Handling
 
 ### Return Pattern
@@ -166,3 +179,34 @@ Find the last `:=`, `=>`, `=`, `<>`, `>=`, `<=`, `>`, `<`, `AND`, `OR`, `NOT` an
 | `:SCLMultilineParams` | Fill multiline parameters for FB/Function call |
 | `:LspSCLFormat` | Format current SCL file |
 | `:SCLGeneratePlcJson` | Generate plc.data.json from data_types/ |
+
+## LSP Server Implementation Notes
+
+### Method Name Conversion
+LSP methods like `textDocument/didOpen` are converted to handler names like `textDocument_didOpen`:
+```lua
+local method_name = message.method:gsub("/", "_")
+local handler = handlers[method_name]
+```
+
+### Request vs Notification
+- Requests have `id` field and require a response
+- Notifications have no `id` and should not receive a response
+```lua
+if message.id then
+  -- Only send response for requests
+  return { id = message.id, result = result }
+end
+```
+
+### Line Ending Handling
+The LSP server strips CRLF (`\r\n`) line endings for Windows compatibility:
+```lua
+line = line:gsub("\r$", "")
+```
+
+### JSON Parser
+The standalone JSON parser in `src/json.lua` handles:
+- Objects, arrays, strings, numbers, booleans, null
+- Escape sequences in strings
+- Whitespace skipping

README.md

@@ -253,10 +253,24 @@ myVar.temperature := 25.5;
 END_FUNCTION_BLOCK
 ```
 
+## Architecture
+
+The plugin uses a standalone LSP server (`src/main.lua`) that communicates via JSON-RPC over stdio. The server handles:
+- Text document synchronization
+- Diagnostics (linting)
+- Formatting
+- Completion, hover, go-to-definition
+- Semantic tokens
+
+The Neovim plugin (`lua/scl_lsp/init.lua`) manages:
+- LSP client lifecycle via `vim.lsp.start()`
+- FileType autocmd for lazy loading
+- blink.cmp integration
+- Workspace scanning for UDTs/DBs
+
 ## Requirements
 
-- **Neovim 0.9+**
-- **nvim-lspconfig** - LSP client
+- **Neovim 0.11+** (uses `vim.lsp.start()`)
 - **nvim-treesitter** - Syntax highlighting
 - **blink.cmp** - Optional, for completion
 - **Lua 5.1+** - LSP server runtime

lua/scl_lsp/init.lua

@@ -13,51 +13,54 @@ function M.setup(opts)
   setup_package_path()
   opts = opts or {}
 
-  local lspconfig_avail, lspconfig = pcall(require, "lspconfig")
-  if not lspconfig_avail then
-    vim.notify("lspconfig not found. Please install nvim-lspconfig.", vim.log.levels.ERROR)
-    return
-  end
-
   local server_path = opts.server_path or vim.fn.expand("~/dev/scl_lsp/src/main.lua")
   
   local root_patterns = { ".git", "data_types", "plc.data.json" }
-  local function get_root_dir(fname)
-    local root = vim.fs.root(fname, root_patterns)
-    return root or vim.fn.fnamemodify(fname, ":h")
-  end
   
-  local function on_attach(client, bufnr)
+  local function start_lsp(bufnr)
+    local fname = vim.api.nvim_buf_get_name(bufnr)
+    if fname == "" then return end
+    
+    local root_dir = vim.fs.root(fname, root_patterns)
+      or vim.fn.fnamemodify(fname, ":p:h")
+    
+    vim.lsp.start({
+      name = "scl_lsp",
+      cmd = { "lua", server_path },
+      root_dir = root_dir,
+      on_attach = function(client, b)
         if opts.lsp and opts.lsp.on_attach then
-      opts.lsp.on_attach(client, bufnr)
+          opts.lsp.on_attach(client, b)
         end
         
-    if opts.lsp.formatting then
-      vim.api.nvim_buf_create_user_command(bufnr, "LspSCLFormat", function()
-        vim.lsp.buf.format({ name = "scl-language-server" })
+        if opts.lsp and opts.lsp.formatting then
+          vim.api.nvim_buf_create_user_command(b, "LspSCLFormat", function()
+            vim.lsp.buf.format({ name = "scl_lsp" })
           end, {})
         end
+      end,
+    })
   end
   
-  lspconfig.scl_lsp = {
-    default_config = {
-      name = "scl-language-server",
-      cmd = { "lua", server_path },
-      filetypes = { "scl" },
-      root_dir = get_root_dir,
-      settings = {},
-      on_attach = on_attach,
-    },
-    docs = {
-      description = "Language server for Siemens SCL (LSP, Linter, Formatter)",
-      default_config = {
-        name = "scl-language-server",
-        cmd = { "lua", server_path },
-        filetypes = { "scl" },
-        root_dir = "root_pattern('.git', 'data_types', 'plc.data.json')",
-      },
-    },
-  }
+  -- Create FileType autocmd for future buffers
+  vim.api.nvim_create_autocmd("FileType", {
+    pattern = "scl",
+    callback = function(args)
+      start_lsp(args.buf)
+    end,
+  })
+  
+  -- Create global format command (works on current buffer)
+  vim.api.nvim_create_user_command("LspSCLFormat", function()
+    vim.lsp.buf.format({ name = "scl_lsp" })
+  end, {})
+  
+  -- Start LSP for any existing scl buffers (handles lazy loading case)
+  for _, bufnr in ipairs(vim.api.nvim_list_bufs()) do
+    if vim.bo[bufnr].filetype == "scl" and vim.api.nvim_buf_is_loaded(bufnr) then
+      start_lsp(bufnr)
+    end
+  end
 
   M.setup_syntax(opts)
   M.setup_multiline_params()