fix(formatter): Implement TIA Portal-compliant SCL formatting

- Default to tabs (not spaces) per TIA Portal standard
- Fix block keyword handling (IF, FOR, WHILE, CASE, REGION, etc.)
- Handle VAR section indentation (variables indented inside VAR)
- Fix IF/ELSIF/ELSE indentation (ELSIF/ELSE at same level as IF)
- Handle CASE labels and nested CASE statements
- Add missing semicolons after END_IF, END_FOR, END_CASE Handle block, etc.
- enders (END_IF, END_REGION, etc.) correctly
- Support compound keywords (END_IF, END_FUNCTION_BLOCK, etc.)

src/formatter.lua

@@ -1,4 +1,5 @@
 -- SCL Formatter - Document formatting for the LSP server
+-- Conforms to TIA Portal SCL formatting standards
 local M = {}
 
 local function position(line, character)
@@ -12,10 +13,45 @@ local function range(start_line, start_char, end_line, end_char)
   }
 end
 
+-- Keywords that start a code block (increase indent AFTER)
+local block_starters = {
+  IF = true, FOR = true, WHILE = true, REPEAT = true,
+  CASE = true, REGION = true,
+}
+
+-- Keywords that stay on same level (don't change indent)
+local same_level_keywords = {
+  THEN = true, ELSE = true, ELSIF = true, DO = true, OF = true,
+}
+
+-- Keywords that end a code block (decrease indent BEFORE)
+local block_enders = {
+  END_IF = true, END_FOR = true, END_WHILE = true, END_REPEAT = true,
+  END_CASE = true, END_REGION = true,
+}
+
+-- Block declaration keywords
+local block_declarations = {
+  FUNCTION = true, FUNCTION_BLOCK = true, ORGANIZATION_BLOCK = true,
+  TYPE = true, STRUCT = true,
+}
+
+-- End block declarations
+local block_declaration_enders = {
+  END_FUNCTION = true, END_FUNCTION_BLOCK = true, END_ORGANIZATION_BLOCK = true,
+  END_TYPE = true, END_STRUCT = true,
+}
+
+-- VAR section keywords
+local var_keywords = {
+  VAR = true, VAR_INPUT = true, VAR_OUTPUT = true, VAR_IN_OUT = true,
+  VAR_TEMP = true, VAR_CONSTANT = true, VAR_RETAIN = true, VAR_NON_RETAIN = true,
+}
+
 function M.format_document(content, options)
   options = options or {}
-  local indent_size = options.indentSize or 4
   local indent_char = options.insertSpaces and " " or "\t"
+  local indent_size = options.tabSize or 1
 
   local lines = {}
   for line in content:gmatch("([^\n]*)\n") do
@@ -27,65 +63,150 @@ function M.format_document(content, options)
 
   local formatted_lines = {}
   local indent_level = 0
+  local if_base_level = nil
+  local in_var_section = false
+  local in_code_section = false
+  local prev_line_keyword = nil
 
   local function get_indent()
     return string.rep(indent_char, indent_level * indent_size)
   end
 
-  local function is_block_keyword(line)
+  local function get_keyword(line)
-    local kw = line:match('^%s*(%w+)')
-    if not kw then return false end
-    local block_keywords = {
-      IF = true, ELSIF = true, ELSE = true,
-      FOR = true, WHILE = true, REPEAT = true,
-      CASE = true,
-      FUNCTION = true, FUNCTION_BLOCK = true, ORGANIZATION_BLOCK = true,
-      TYPE = true, STRUCT = true,
-    }
-    return block_keywords[kw]
-  end
-
-  local function is_end_block(line)
-    local kw = line:match('^%s*(%w+)')
-    if not kw then return false end
-    local end_keywords = {
-      END_IF = true, END_FOR = true, END_WHILE = true, END_REPEAT = true,
-      END_CASE = true, END_FUNCTION = true, END_FUNCTION_BLOCK = true,
-      END_ORGANIZATION_BLOCK = true, END_TYPE = true, END_STRUCT = true,
-    }
-    return end_keywords[kw]
-  end
-
-  local function process_line(line)
     local trimmed = line:gsub("^%s+", ""):gsub("%s+$", "")
+    local kw = trimmed:match("^(%w+)")
+    return kw, trimmed
+  end
 
-    if trimmed == "" or trimmed:match("^//") or trimmed:match("^%(%*") then
+  local function is_block_starter(kw)
+    return kw and block_starters[kw]
+  end
+
+  local function is_block_ender(kw)
+    return kw and block_enders[kw]
+  end
+
+  local function is_var_keyword(kw)
+    return kw and var_keywords[kw]
+  end
+
+  local function is_block_declaration(kw)
+    return kw and block_declarations[kw]
+  end
+
+  local function is_block_declaration_ender(kw)
+    return kw and block_declaration_enders[kw]
+  end
+
+  local function needs_semicolon(trimmed)
+    local kw = trimmed:match("^(%w+_%w+)") or trimmed:match("^(%w+)")
+    if not kw then return false end
+    local needs_end = {
+      END_IF = true, END_FOR = true, END_WHILE = true, END_REPEAT = true,
+      END_CASE = true, END_REGION = true,
+      END_FUNCTION = true, END_FUNCTION_BLOCK = true, END_ORGANIZATION_BLOCK = true,
+      END_TYPE = true, END_STRUCT = true,
+    }
+    if needs_end[kw] then
+      local last_char = trimmed:sub(-1)
+      return last_char ~= ";" and last_char ~= "("
+    end
+    return false
+  end
+
+  local function is_case_label(trimmed)
+    return trimmed:match("^%w+%s*:") ~= nil
+  end
+
+  for i, line in ipairs(lines) do
+    local trimmed = line:gsub("^%s+", ""):gsub("%s+$", "")
+    
+    -- Extract full keyword (handle compound keywords like END_IF, END_FUNCTION_BLOCK)
+    local kw = trimmed:match("^(%w+_%w+)") or trimmed:match("^(%w+)")
+
+    -- Preserve empty lines and comments as-is
+    if trimmed == "" or trimmed:match("^//") or trimmed:match("^%(%*") or trimmed:match("^%*/") then
       table.insert(formatted_lines, line)
-      return
+    else
-    end
+      -- Check for BEGIN keyword (starts code section)
-
+      if kw == "BEGIN" then
-    if is_end_block(trimmed) then
+        in_code_section = true
-      indent_level = math.max(0, indent_level - 1)
+        table.insert(formatted_lines, get_indent() .. trimmed)
-    end
+        indent_level = 1
-
+      -- Check for VAR section start
-    local formatted_line = get_indent() .. trimmed
+      elseif is_var_keyword(kw) then
-    table.insert(formatted_lines, formatted_line)
+        in_var_section = true
-
+        in_code_section = false
-    if is_block_keyword(trimmed) and not is_end_block(trimmed) then
+        indent_level = 0
-      if not trimmed:match("CASE%s+.+OF%s*$") and
+        table.insert(formatted_lines, get_indent() .. trimmed)
-         not trimmed:match("IF%s+.+THEN%s*$") and
+        indent_level = 1
-         not trimmed:match("ELSIF%s+.+THEN%s*$") and
+      -- Check for END_VAR
-         not trimmed:match("ELSE%s*$") and
+      elseif kw == "END_VAR" then
-         not trimmed:match("FOR%s+.+DO%s*$") and
+        in_var_section = false
-         not trimmed:match("WHILE%s+.+DO%s*$") and
+        indent_level = 0
-         not trimmed:match("REPEAT%s*$") then
+        table.insert(formatted_lines, get_indent() .. trimmed)
+      -- Check for block declaration enders
+      elseif is_block_declaration_ender(kw) then
+        indent_level = math.max(0, indent_level - 1)
+        local formatted_line = get_indent() .. trimmed
+        if needs_semicolon(trimmed) then
+          formatted_line = formatted_line .. ";"
+        end
+        table.insert(formatted_lines, formatted_line)
+      -- Check for block declaration starters (FUNCTION, FUNCTION_BLOCK, etc.)
+      elseif is_block_declaration(kw) then
+        table.insert(formatted_lines, get_indent() .. trimmed)
+        indent_level = 0
+      -- Check for block enders
+      elseif is_block_ender(kw) then
+        if kw == "END_IF" then
+          if_base_level = nil
+        end
+        indent_level = math.max(0, indent_level - 1)
+        local formatted_line = get_indent() .. trimmed
+        if needs_semicolon(trimmed) then
+          formatted_line = formatted_line .. ";"
+        end
+        table.insert(formatted_lines, formatted_line)
+      -- Check for CASE label
+      -- Check for CASE labels (like "1:")
+      elseif is_case_label(trimmed) and prev_line_keyword == "CASE" then
+        -- CASE label stays at same indent as CASE (already increased)
+        local formatted_line = get_indent() .. trimmed
+        table.insert(formatted_lines, formatted_line)
+        -- Increase for content after label
         indent_level = indent_level + 1
+      -- Check for same-level keywords (THEN, ELSE, DO, OF on their own line)
+      elseif same_level_keywords[kw] then
+        -- For ELSIF and ELSE, reset to IF base level
+        if (kw == "ELSIF" or kw == "ELSE") and if_base_level then
+          indent_level = if_base_level
+        end
+        table.insert(formatted_lines, get_indent() .. trimmed)
+        -- After ELSE/ELSIF, increase indent for content
+        if (kw == "ELSIF" or kw == "ELSE") and if_base_level then
+          indent_level = indent_level + 1
+        end
+      -- Check for block starters
+      elseif is_block_starter(kw) then
+        -- Save base level for IF statements
+        if kw == "IF" then
+          if_base_level = indent_level
+        end
+        table.insert(formatted_lines, get_indent() .. trimmed)
+        -- Always increase indent after block starters
+        indent_level = indent_level + 1
+      -- Regular line
+      else
+        local formatted_line = get_indent() .. trimmed
+        if needs_semicolon(trimmed) then
+          formatted_line = formatted_line .. ";"
+        end
+        table.insert(formatted_lines, formatted_line)
       end
     end
-  end
 
-  for _, line in ipairs(lines) do
+    prev_line_keyword = kw
-    process_line(line)
   end
 
   local result = table.concat(formatted_lines, "\n")
@@ -103,8 +224,8 @@ end
 
 function M.get_formatting_options()
   return {
-    insertSpaces = true,
+    insertSpaces = false,
-    tabSize = 4,
+    tabSize = 1,
     trimTrailingWhitespace = true,
     insertFinalNewline = true,
     trimFinalNewlines = true,