Enhance error handling in Read-LuaString and Read-LuaTable; validate escape sequences and ensure table keys are not nil

Author: MariusStorhaug

src/functions/private/Read-LuaString.ps1

@@ -73,6 +73,9 @@
                             $hexStr = $script:luaString.Substring(
                                 $script:luaPos, 2
                             )
+                            if ($hexStr -notmatch '^[0-9a-fA-F]{2}$') {
+                                throw 'Invalid \x escape sequence: expected two hexadecimal digits.'
+                            }
                             $hexVal = [Convert]::ToInt32($hexStr, 16)
                             $null = $result.Append([char]$hexVal)
                             $script:luaPos += 2
@@ -91,6 +94,9 @@
                                 $script:luaString[$script:luaPos] -ne '}') {
                                 $script:luaPos++
                             }
+                            if ($script:luaPos -ge $script:luaString.Length) {
+                                throw 'Invalid \u escape sequence: missing closing brace.'
+                            }
                             $hexStr = $script:luaString.Substring(
                                 $hexStart,
                                 $script:luaPos - $hexStart

src/functions/private/Read-LuaTable.ps1

@@ -44,6 +44,9 @@
                 $script:luaPos++ # skip [
                 Skip-LuaWhitespace
                 $key = Read-LuaValue
+                if ($null -eq $key) {
+                    throw 'Lua table keys cannot be nil.'
+                }
                 Skip-LuaWhitespace
                 if ($script:luaPos -ge $script:luaString.Length -or
                     $script:luaString[$script:luaPos] -ne ']') {