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+**
+- **Neovim 0.11+** (uses `vim.lsp.start()`)
-- **nvim-lspconfig** - LSP client
 - **nvim-treesitter** - Syntax highlighting
 - **blink.cmp** - Optional, for completion
 - **Lua 5.1+** - LSP server runtime

src/diagnostics.lua

@@ -1,6 +1,21 @@
 -- SCL Diagnostics - Linter functionality for the LSP server
 local M = {}
-local parser = require("scl_lsp.parser")
+
+-- Get script path for loading parser (same pattern as main.lua)
+local script_path = debug.getinfo(1, "S").source:gsub("^@", ""):match("(.*/)") or ""
+if script_path == "" then
+  script_path = "."
+end
+if script_path:sub(1, 1) ~= "/" then
+  local cwd = io.popen("pwd")
+  if cwd then
+    script_path = cwd:read("*l") .. "/" .. script_path
+    cwd:close()
+  end
+end
+package.path = package.path .. ";" .. script_path .. "/?.lua"
+
+local parser = dofile(script_path .. "/parser.lua")
 
 local DiagnosticSeverity = {
   Error = 1,
@@ -19,7 +34,7 @@ end
 local function range_to_lsp(start_line, start_char, end_line, end_char)
   return {
     start = position_to_lsp(start_line, start_char),
-    end = position_to_lsp(end_line, end_char),
+    ["end"] = position_to_lsp(end_line, end_char),
   }
 end
 

src/formatter.lua

@@ -8,7 +8,7 @@ end
 local function range(start_line, start_char, end_line, end_char)
   return {
     start = position(start_line, start_char),
-    end = position(end_line, end_char),
+    ["end"] = position(end_line, end_char),
   }
 end
 

src/json.lua

@@ -13,7 +13,7 @@ end
 
 local function escape(s)
   s = s:gsub("\\", "\\\\")
-  s = s:gsub("\"", "\\\"")
+  s = s:gsub('"', '\\"')
   s = s:gsub("\n", "\\n")
   s = s:gsub("\r", "\\r")
   s = s:gsub("\t", "\\t")
@@ -29,7 +29,7 @@ function json.encode(data)
   elseif t == "number" then
     return tostring(data)
   elseif t == "string" then
-    return "\"" .. escape(data) .. "\""
+    return '"' .. escape(data) .. '"'
   elseif t == "table" then
     local parts = {}
     if is_array(data) then
@@ -39,7 +39,7 @@ function json.encode(data)
       return "[" .. table.concat(parts, ",") .. "]"
     else
       for k, v in pairs(data) do
-        table.insert(parts, "\"" .. escape(k) .. "\":" .. json.encode(v))
+        table.insert(parts, '"' .. escape(k) .. '":' .. json.encode(v))
       end
       return "{" .. table.concat(parts, ",") .. "}"
     end
@@ -49,7 +49,7 @@ function json.encode(data)
 end
 
 local function skip_whitespace(s, i)
-  while i <= #s and s:find("^%s", i) do
+  while i <= #s and s:sub(i, i):match("%s") do
     i = i + 1
   end
   return i
@@ -60,7 +60,7 @@ local function parse_string(s, i)
   i = i + 1
   while i <= #s do
     local c = s:sub(i, i)
-    if c == "\"" then
+    if c == '"' then
       return table.concat(result), i + 1
     elseif c == "\\" and i < #s then
       local next_c = s:sub(i + 1, i + 1)
@@ -70,9 +70,9 @@ local function parse_string(s, i)
         table.insert(result, "\r")
       elseif next_c == "t" then
         table.insert(result, "\t")
-      elseif next_c == "\\\"" then
+      elseif next_c == '"' then
-        table.insert(result, "\"")
+        table.insert(result, '"')
-      elseif next_c == "\\\\" then
+      elseif next_c == "\\" then
         table.insert(result, "\\")
       else
         table.insert(result, next_c)
@@ -91,28 +91,85 @@ local function parse_number(s, i)
   if s:sub(i, i) == "-" then
     i = i + 1
   end
-  while i <= #s and s:find("^%d", s:sub(i, i)) do
+  while i <= #s and s:sub(i, i):match("%d") do
     i = i + 1
   end
   if s:sub(i, i) == "." then
     i = i + 1
-    while i <= #s and s:find("^%d", s:sub(i, i)) do
+    while i <= #s and s:sub(i, i):match("%d") do
       i = i + 1
     end
   end
-  if s:sub(i, i):find("^[eE]") then
+  if s:sub(i, i):match("[eE]") then
     i = i + 1
-    if s:sub(i, i):find("^[+-]") then
+    if s:sub(i, i):match("[+-]") then
       i = i + 1
     end
-    while i <= #s and s:find("^%d", s:sub(i, i)) do
+    while i <= #s and s:sub(i, i):match("%d") do
       i = i + 1
     end
   end
   return tonumber(s:sub(start, i - 1)), i
 end
 
-local function parse_value(s, i)
+local parse_value
+
+local function parse_array(s, i)
+  local arr = {}
+  i = i + 1
+  while i <= #s do
+    i = skip_whitespace(s, i)
+    if s:sub(i, i) == "]" then
+      return arr, i + 1
+    end
+    local val
+    val, i = parse_value(s, i)
+    table.insert(arr, val)
+    i = skip_whitespace(s, i)
+    if s:sub(i, i) == "]" then
+      return arr, i + 1
+    end
+    if s:sub(i, i) == "," then
+      i = i + 1
+    end
+  end
+  return nil, i
+end
+
+local function parse_object(s, i)
+  local obj = {}
+  i = i + 1
+  while i <= #s do
+    i = skip_whitespace(s, i)
+    if s:sub(i, i) == "}" then
+      return obj, i + 1
+    end
+    if s:sub(i, i) == '"' then
+      local key
+      key, i = parse_string(s, i)
+      i = skip_whitespace(s, i)
+      if s:sub(i, i) ~= ":" then
+        return nil, i
+      end
+      i = i + 1
+      local val
+      val, i = parse_value(s, i)
+      obj[key] = val
+      i = skip_whitespace(s, i)
+      if s:sub(i, i) == "}" then
+        return obj, i + 1
+      end
+      if s:sub(i, i) == "," then
+        i = i + 1
+      end
+    else
+      return nil, i
+    end
+  end
+  return nil, i
+end
+
+parse_value = function(s, i)
   i = skip_whitespace(s, i)
   if i > #s then
     return nil, i
@@ -121,66 +178,30 @@ local function parse_value(s, i)
   local c = s:sub(i, i)
 
   if c == "{" then
-    local obj = {}
+    return parse_object(s, i)
-    i = i + 1
-    while i <= #s do
-      i = skip_whitespace(s, i)
-      if s:sub(i, i) == "}" then
-        return obj, i + 1
-      end
-      if s:sub(i, i) == "\"" then
-        local key
-        key, i = parse_string(s, i)
-        i = skip_whitespace(s, i)
-        if s:sub(i, i) ~= ":" then
-          return nil, i
-        end
-        i = i + 1
-        local val
-        val, i = parse_value(s, i)
-        obj[key] = val
-        i = skip_whitespace(s, i)
-        if s:sub(i, i) == "}" then
-          return obj, i + 1
-        end
-        if s:sub(i, i) == "," then
-          i = i + 1
-        end
-      else
-        return nil, i
-      end
-    end
-    return nil, i
   elseif c == "[" then
-    local arr = {}
+    return parse_array(s, i)
-    i = i + 1
+  elseif c == '"' then
-    while i <= #s do
+    return parse_string(s, i)
-      i = skip_whitespace(s, i)
+  elseif c == "t" then
-      if s:sub(i, i) == "]" then
+    if s:sub(i, i + 3) == "true" then
-        return arr, i + 1
+      return true, i + 4
-      end
-      local val
-      val, i = parse_value(s, i)
-      table.insert(arr, val)
-      i = skip_whitespace(s, i)
-      if s:sub(i, i) == "]" then
-        return arr, i + 1
-      end
-      if s:sub(i, i) == "," then
-        i = i + 1
-      end
     end
     return nil, i
-  elseif c == "\"" then
+  elseif c == "f" then
-    return parse_string(s, i)
+    if s:sub(i, i + 4) == "false" then
-  elseif s:sub(i, i + 3) == "null" then
+      return false, i + 5
-    return nil, i + 4
+    end
-  elseif s:sub(i, i + 3) == "true" then
+    return nil, i
-    return true, i + 4
+  elseif c == "n" then
-  elseif s:sub(i, i + 4) == "false" then
+    if s:sub(i, i + 3) == "null" then
-    return false, i + 5
+      return nil, i + 4
-  else
+    end
+    return nil, i
+  elseif c == "-" or c:match("%d") then
     return parse_number(s, i)
+  else
+    return nil, i
   end
 end
 

src/main.lua

@@ -296,7 +296,7 @@ function handlers.textDocument_hover(params)
 			contents = { kind = "markdown", value = detail },
 			range = {
 				start = { line = params.position.line, character = word_start - 1 },
-				endPos = { line = params.position.line, character = word_end - 1 },
+				["end"] = { line = params.position.line, character = word_end - 1 },
 			},
 		}
 	end
@@ -315,7 +315,7 @@ function handlers.textDocument_hover(params)
 					contents = { kind = "markdown", value = detail },
 					range = {
 						start = { line = params.position.line, character = word_start - 1 },
-						endPos = { line = params.position.line, character = word_end - 1 },
+						["end"] = { line = params.position.line, character = word_end - 1 },
 					},
 				}
 			end
@@ -449,7 +449,7 @@ function handlers.textDocument_definition(params)
 			uri = uri,
 			range = {
 				start = { line = pos.line, character = pos.character },
-				endPos = { line = pos.line, character = pos.character + #word },
+				["end"] = { line = pos.line, character = pos.character + #word },
 			},
 		}
 	end
@@ -478,10 +478,10 @@ function handlers.textDocument_documentSymbol(params)
 			table.insert(symbols, {
 				name = func.kind:upper() .. " " .. func.name,
 				kind = kind_map[func.kind] or 14,
-				range = { start = { line = func.start, character = 0 }, endPos = { line = func.final, character = 0 } },
+				range = { start = { line = func.start, character = 0 }, ["end"] = { line = func.final, character = 0 } },
 				selectionRange = {
 					start = { line = func.start, character = 0 },
-					endPos = { line = func.start, character = #func.name },
+					["end"] = { line = func.start, character = #func.name },
 				},
 				containerName = nil,
 			})
@@ -500,11 +500,11 @@ function handlers.textDocument_documentSymbol(params)
 				detail = var_info.type or "VAR",
 				range = {
 					start = { line = var_info.line, character = 0 },
-					endPos = { line = var_info.line, character = #var_name },
+					["end"] = { line = var_info.line, character = #var_name },
 				},
 				selectionRange = {
 					start = { line = var_info.line, character = var_info.character },
-					endPos = { line = var_info.line, character = var_info.character + #var_name },
+					["end"] = { line = var_info.line, character = var_info.character + #var_name },
 				},
 				containerName = nil,
 			})
@@ -526,11 +526,11 @@ function handlers.textDocument_documentSymbol(params)
 				detail = detail,
 				range = {
 					start = { line = type_info.start_line or 0, character = 0 },
-					endPos = { line = type_info.start_line or 0, character = #type_name },
+					["end"] = { line = type_info.start_line or 0, character = #type_name },
 				},
 				selectionRange = {
 					start = { line = type_info.start_line or 0, character = 0 },
-					endPos = { line = type_info.start_line or 0, character = #type_name },
+					["end"] = { line = type_info.start_line or 0, character = #type_name },
 				},
 				containerName = nil,
 			})
@@ -656,6 +656,10 @@ function handlers.textDocument_semanticTokensRange(params)
 	return handlers.textDocument_semanticTokensFull(params)
 end
 
+-- Aliases for method names with slashes converted to underscores
+handlers["textDocument_semanticTokens_full"] = handlers.textDocument_semanticTokensFull
+handlers["textDocument_semanticTokens_range"] = handlers.textDocument_semanticTokensRange
+
 function handlers.textDocument_inlayHint(params)
 	local uri = params.textDocument.uri
 	local doc = documents[uri]
@@ -708,7 +712,7 @@ function handlers.workspace_symbol(params)
 				uri = uri,
 				range = {
 					start = { line = line, character = col },
-					endPos = { line = line, character = col + length },
+					["end"] = { line = line, character = col + length },
 				},
 			},
 		})
@@ -848,17 +852,26 @@ local function handle_message(message)
 	if message.method == "$/cancelRequest" then
 		return nil
 	end
-	local handler = handlers[message.method]
+	-- Convert method name from "textDocument/didOpen" to "textDocument_didOpen"
+	local method_name = message.method:gsub("/", "_")
+	local handler = handlers[method_name]
 	if handler then
 		local ok, result = pcall(handler, message.params)
-		if ok then
+		-- Only return response for requests (have id), not notifications
-			return { id = message.id, result = result }
+		if message.id then
-		else
+			if ok then
-			return { id = message.id, error = { code = -32603, message = tostring(result) } }
+				return { id = message.id, result = result }
+			else
+				return { id = message.id, error = { code = -32603, message = tostring(result) } }
+			end
 		end
 	else
-		return { id = message.id, error = { code = -32601, message = "Method not found: " .. message.method } }
+		-- Only return error for requests (have id)
+		if message.id then
+			return { id = message.id, error = { code = -32601, message = "Method not found: " .. message.method } }
+		end
 	end
+	return nil
 end
 
 local function main()
@@ -871,6 +884,9 @@ local function main()
 		if not line then
 			break
 		end
+		-- Strip trailing \r (Windows line endings)
+		line = line:gsub("\r$", "")
+		
 		if line:match("^Content%-Length:%s*(%d+)") then
 			content_length = tonumber(line:match("^Content%-Length:%s*(%d+)"))
 		elseif line == "" then