process: migrate arg validation and checking to Lua

data/core/process.lua

@@ -0,0 +1,50 @@
+local function env_key(str)
+  if PLATFORM == "Windows" then return str:upper() else return str end
+end
+
+---Sorts the environment variable by its key, converted to uppercase.
+---This is only needed on Windows.
+local function compare_env(a, b)
+  return env_key(a:match("([^=]*)=")) < env_key(b:match("([^=]*)="))
+end
+
+local old_start = process.start
+function process.start(command, options)
+  assert(type(command) == "table" or type(command) == "string", "invalid argument #1 to process.start(), expected string or table, got "..type(command))
+  assert(type(options) == "table" or type(options) == "nil", "invalid argument #2 to process.start(), expected table or nil, got "..type(options))
+  if PLATFORM == "Windows" then
+    if type(command) == "table" then
+      -- escape the arguments into a command line string
+      -- https://github.com/python/cpython/blob/48f9d3e3faec5faaa4f7c9849fecd27eae4da213/Lib/subprocess.py#L531
+      local arglist = {}
+      for _, v in ipairs(command) do
+        local backslash, arg = 0, {}
+        for c in v:gmatch(".") do
+          if     c == "\\" then backslash = backslash + 1
+          elseif c == '"'  then arg[#arg+1] = string.rep("\\", backslash * 2 + 1)..'"'; backslash = 0
+          else                  arg[#arg+1] = string.rep("\\", backslash) .. c;         backslash = 0 end
+        end
+        arg[#arg+1] = string.rep("\\", backslash) -- add remaining backslashes
+        if #v == 0 or v:find("[\t\v\r\n ]") then arglist[#arglist+1] = '"'..table.concat(arg, "")..'"'
+        else                                     arglist[#arglist+1] = table.concat(arg, "") end
+      end
+      command = table.concat(arglist, " ")
+    end
+  else
+    command = type(command) == "table" and command or { command }
+  end
+  if type(options) == "table" and options.env then
+    local user_env = options.env --[[@as table]]
+    options.env = function(system_env)
+      local final_env, envlist = {}, {}
+      for k, v in pairs(system_env) do final_env[env_key(k)] = k.."="..v end
+      for k, v in pairs(user_env)   do final_env[env_key(k)] = k.."="..v end
+      for _, v in pairs(final_env)  do envlist[#envlist+1] = v end
+      if PLATFORM == "Windows" then table.sort(envlist, compare_env) end
+      return table.concat(envlist, "\0").."\0\0"
+    end
+  end
+  return old_start(command, options)
+end
+
+return process

data/core/start.lua

@@ -46,6 +46,7 @@ table.unpack = table.unpack or unpack
 bit32 = bit32 or require "core.bit"
 
 require "core.utf8string"
+require "core.process"
 
 -- Because AppImages change the working directory before running the executable,
 -- we need to change it back to the original one.