path: root/plugins/lite-debugger.lua

-- mod-version:3

local command = require "core.command"
local core = require "core"

--[[
   Upstream https://github.com/slembcke/debugger.lua
   with changes to allow for breakpoints for better debugging

   Copyright (c) 2020 Scott Lembcke and Howling Moon Software
   
   Permission is hereby granted, free of charge, to any person obtaining a copy
   of this software and associated documentation files (the "Software"), to deal
   in the Software without restriction, including without limitation the rights
   to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
   copies of the Software, and to permit persons to whom the Software is
   furnished to do so, subject to the following conditions:
   
   The above copyright notice and this permission notice shall be included in
   all copies or substantial portions of the Software.
   
   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
   SOFTWARE.
   
   TODO:
   * Print short function arguments as part of stack location.
   * Properly handle being reentrant due to coroutines.
]]

local dbg

-- Use ANSI color codes in the prompt by default.
local COLOR_GRAY = ""
local COLOR_RED = ""
local COLOR_BLUE = ""
local COLOR_YELLOW = ""
local COLOR_RESET = ""
local GREEN_CARET = " => "

local function pretty(obj, max_depth)
   if max_depth == nil then max_depth = dbg.pretty_depth end
   
   -- Returns true if a table has a __tostring metamethod.
   local function coerceable(tbl)
      local meta = getmetatable(tbl)
      return (meta and meta.__tostring)
   end
   
   local function recurse(obj, depth)
      if type(obj) == "string" then
         -- Dump the string so that escape sequences are printed.
         return string.format("%q", obj)
      elseif type(obj) == "table" and depth < max_depth and not coerceable(obj) then
         local str = "{"
         
         for k, v in pairs(obj) do
            local pair = pretty(k, 0).." = "..recurse(v, depth + 1)
            str = str..(str == "{" and pair or ", "..pair)
         end
         
         return str.."}"
      else
         -- tostring() can fail if there is an error in a __tostring metamethod.
         local success, value = pcall(function() return tostring(obj) end)
         return (success and value or "<!!error in __tostring metamethod!!>")
      end
   end
   
   return recurse(obj, 0)
end

-- The stack level that cmd_* functions use to access locals or info
-- The structure of the code very carefully ensures this.
local CMD_STACK_LEVEL = 6

-- Location of the top of the stack outside of the debugger.
-- Adjusted by some debugger entrypoints.
local stack_top = 0

-- The current stack frame index.
-- Changed using the up/down commands
local stack_inspect_offset = 0

-- LuaJIT has an off by one bug when setting local variables.
local LUA_JIT_SETLOCAL_WORKAROUND = 0

-- Default dbg.read function
local function dbg_read(prompt)
   dbg.write(prompt)
   io.flush()
   return io.read()
end

-- Default dbg.write function
local function dbg_write(str)
   io.write(str)
end

local function dbg_writeln(str, ...)
   if select("#", ...) == 0 then
      dbg.write((str or "<NULL>").."\n")
   else
      dbg.write(string.format(str.."\n", ...))
   end
end

local function format_loc(file, line) return COLOR_BLUE..file..COLOR_RESET..":"..COLOR_YELLOW..line..COLOR_RESET end
local function format_stack_frame_info(info)
   local filename = info.source:match("@(.*)")
   local source = filename and dbg.shorten_path(filename) or info.short_src
   local namewhat = (info.namewhat == "" and "chunk at" or info.namewhat)
   local name = (info.name and "'"..COLOR_BLUE..info.name..COLOR_RESET.."'" or format_loc(source, info.linedefined))
   return format_loc(source, info.currentline).." in "..namewhat.." "..name
end

local repl

-- Return false for stack frames without source,
-- which includes C frames, Lua bytecode, and `loadstring` functions
local function frame_has_line(info) return info.currentline >= 0 end

local function hook_factory(repl_threshold)
   return function(offset, reason)
      return function(event, _)
         -- Skip events that don't have line information.
         if not frame_has_line(debug.getinfo(2)) then return end
         
         -- Tail calls are specifically ignored since they also will have tail returns to balance out.
         if event == "call" then
            offset = offset + 1
         elseif event == "return" and offset > repl_threshold then
            offset = offset - 1
         elseif event == "line" and offset <= repl_threshold then
            repl(reason)
         end
      end
   end
end

local hook_step = hook_factory(1)
local hook_next = hook_factory(0)
local hook_finish = hook_factory(-1)
local hook_break = hook_factory(1)

-- Create a table of all the locally accessible variables.
-- Globals are not included when running the locals command, but are when running the print command.
local function local_bindings(offset, include_globals)
   local level = offset + stack_inspect_offset + CMD_STACK_LEVEL
   local func = debug.getinfo(level).func
   local bindings = {}
   
   -- Retrieve the upvalues
   do local i = 1; while true do
      local name, value = debug.getupvalue(func, i)
      if not name then break end
      bindings[name] = value
      i = i + 1
   end end
   
   -- Retrieve the locals (overwriting any upvalues)
   do local i = 1; while true do
      local name, value = debug.getlocal(level, i)
      if not name then break end
      bindings[name] = value
      i = i + 1
   end end
   
   -- Retrieve the varargs (works in Lua 5.2 and LuaJIT)
   local varargs = {}
   do local i = 1; while true do
      local name, value = debug.getlocal(level, -i)
      if not name then break end
      varargs[i] = value
      i = i + 1
   end end
   if #varargs > 0 then bindings["..."] = varargs end
   
   if include_globals then
      -- In Lua 5.2, you have to get the environment table from the function's locals.
      local env = (_VERSION <= "Lua 5.1" and getfenv(func) or bindings._ENV)
      return setmetatable(bindings, {__index = env or _G})
   else
      return bindings
   end
end

-- Used as a __newindex metamethod to modify variables in cmd_eval().
local function mutate_bindings(_, name, value)
   local FUNC_STACK_OFFSET = 3 -- Stack depth of this function.
   local level = stack_inspect_offset + FUNC_STACK_OFFSET + CMD_STACK_LEVEL
   
   -- Set a local.
   do local i = 1; repeat
      local var = debug.getlocal(level, i)
      if name == var then
         dbg_writeln(COLOR_YELLOW.."debugger.lua"..GREEN_CARET.."Set local variable "..COLOR_BLUE..name..COLOR_RESET)
         return debug.setlocal(level + LUA_JIT_SETLOCAL_WORKAROUND, i, value)
      end
      i = i + 1
   until var == nil end
   
   -- Set an upvalue.
   local func = debug.getinfo(level).func
   do local i = 1; repeat
      local var = debug.getupvalue(func, i)
      if name == var then
         dbg_writeln(COLOR_YELLOW.."debugger.lua"..GREEN_CARET.."Set upvalue "..COLOR_BLUE..name..COLOR_RESET)
         return debug.setupvalue(func, i, value)
      end
      i = i + 1
   until var == nil end
   
   -- Set a global.
   dbg_writeln(COLOR_YELLOW.."debugger.lua"..GREEN_CARET.."Set global variable "..COLOR_BLUE..name..COLOR_RESET)
   _G[name] = value
end

-- Compile an expression with the given variable bindings.
local function compile_chunk(block, env)
   local source = "debugger.lua REPL"
   local chunk = nil
   
   if _VERSION <= "Lua 5.1" then
      chunk = loadstring(block, source)
      if chunk then setfenv(chunk, env) end
   else
      -- The Lua 5.2 way is a bit cleaner
      chunk = load(block, source, "t", env)
   end
   
   if not chunk then dbg_writeln(COLOR_RED.."Error: Could not compile block:\n"..COLOR_RESET..block) end
   return chunk
end

local SOURCE_CACHE = {}

local function where(info, context_lines)
   local source = SOURCE_CACHE[info.source]
   if not source then
      source = {}
      local filename = info.source:match("@(.*)")
      if filename then
         pcall(function() for line in io.lines(filename) do table.insert(source, line) end end)
      elseif info.source then
         for line in info.source:gmatch("(.-)\n") do table.insert(source, line) end
      end
      SOURCE_CACHE[info.source] = source
   end
   
   if source and source[info.currentline] then
      for i = info.currentline - context_lines, info.currentline + context_lines do
         local tab_or_caret = (i == info.currentline and  GREEN_CARET or "    ")
         local line = source[i]
         if line then dbg_writeln(COLOR_GRAY.."% 4d"..tab_or_caret.."%s", i, line) end
      end
   else
      dbg_writeln(COLOR_RED.."Error: Source not available for "..COLOR_BLUE..info.short_src);
   end
   
   return false
end

-- Wee version differences
local unpack = table.unpack
local pack = function(...) return {n = select("#", ...), ...} end

local break_funcs = {}

local function cmd_break(func_name)
   table.insert(break_funcs, func_name)
   return false
end

local function cmd_delete(index)
   index = tonumber(index)
   if index > #break_funcs then
      dbg_writeln(COLOR_RED.."Error:"..COLOR_RESET.." no breakpoint "..index)
   else
      table.remove(break_funcs, index)
   end
   return false
end

local function cmd_step()
   stack_inspect_offset = stack_top
   return true, hook_step
end

local function cmd_next()
   stack_inspect_offset = stack_top
   return true, hook_next
end

local function cmd_finish()
   local offset = stack_top - stack_inspect_offset
   stack_inspect_offset = stack_top
   return true, offset < 0 and hook_factory(offset - 1) or hook_finish
end

local function cmd_print(expr)
   local env = local_bindings(1, true)
   local chunk = compile_chunk("return "..expr, env)
   if chunk == nil then return false end
   
   -- Call the chunk and collect the results.
   local results = pack(pcall(chunk, unpack(rawget(env, "...") or {})))
   
   -- The first result is the pcall error.
   if not results[1] then
      dbg_writeln(COLOR_RED.."Error:"..COLOR_RESET.." "..results[2])
   else
      local output = ""
      for i = 2, results.n do
         output = output..(i ~= 2 and ", " or "")..pretty(results[i])
      end
      
      if output == "" then output = "<no result>" end
      dbg_writeln(COLOR_BLUE..expr.. GREEN_CARET..output)
   end
   
   return false
end

local function cmd_eval(code)
   local env = local_bindings(1, true)
   local mutable_env = setmetatable({}, {
      __index = env,
      __newindex = mutate_bindings,
   })
   
   local chunk = compile_chunk(code, mutable_env)
   if chunk == nil then return false end
   
   -- Call the chunk and collect the results.
   local success, err = pcall(chunk, unpack(rawget(env, "...") or {}))
   if not success then
      dbg_writeln(COLOR_RED.."Error:"..COLOR_RESET.." "..tostring(err))
   end
   
   return false
end

local function cmd_down()
   local offset = stack_inspect_offset
   local info
   
   repeat -- Find the next frame with a file.
      offset = offset + 1
      info = debug.getinfo(offset + CMD_STACK_LEVEL)
   until not info or frame_has_line(info)
   
   if info then
      stack_inspect_offset = offset
      dbg_writeln("Inspecting frame: "..format_stack_frame_info(info))
      if tonumber(dbg.auto_where) then where(info, dbg.auto_where) end
   else
      info = debug.getinfo(stack_inspect_offset + CMD_STACK_LEVEL)
      dbg_writeln("Already at the bottom of the stack.")
   end
   
   return false
end

local function cmd_up()
   local offset = stack_inspect_offset
   local info
   
   repeat -- Find the next frame with a file.
      offset = offset - 1
      if offset < stack_top then info = nil; break end
      info = debug.getinfo(offset + CMD_STACK_LEVEL)
   until frame_has_line(info)
   
   if info then
      stack_inspect_offset = offset
      dbg_writeln("Inspecting frame: "..format_stack_frame_info(info))
      if tonumber(dbg.auto_where) then where(info, dbg.auto_where) end
   else
      info = debug.getinfo(stack_inspect_offset + CMD_STACK_LEVEL)
      dbg_writeln("Already at the top of the stack.")
   end
   
   return false
end

local function cmd_where(context_lines)
   local info = debug.getinfo(stack_inspect_offset + CMD_STACK_LEVEL)
   return (info and where(info, tonumber(context_lines) or 5))
end

local function cmd_trace()
   dbg_writeln("Inspecting frame %d", stack_inspect_offset - stack_top)
   local i = 0; while true do
      local info = debug.getinfo(stack_top + CMD_STACK_LEVEL + i)
      if not info then break end
      
      local is_current_frame = (i + stack_top == stack_inspect_offset)
      local tab_or_caret = (is_current_frame and  GREEN_CARET or "    ")
      dbg_writeln(COLOR_GRAY.."% 4d"..COLOR_RESET..tab_or_caret.."%s", i, format_stack_frame_info(info))
      i = i + 1
   end
   
   return false
end

local function cmd_locals()
   local bindings = local_bindings(1, false)
   
   -- Get all the variable binding names and sort them
   local keys = {}
   for k, _ in pairs(bindings) do table.insert(keys, k) end
   table.sort(keys)
   
   for _, k in ipairs(keys) do
      local v = bindings[k]
      
      -- Skip the debugger object itself, "(*internal)" values, and Lua 5.2's _ENV object.
      if not rawequal(v, dbg) and k ~= "_ENV" and not k:match("%(.*%)") then
         dbg_writeln("  "..COLOR_BLUE..k.. GREEN_CARET..pretty(v))
      end
   end
   
   return false
end

local function cmd_help()
   dbg.write(""
      .. COLOR_BLUE.."  <return>"..GREEN_CARET.."re-run last command\n"
      .. COLOR_BLUE.."  c"..COLOR_YELLOW.."(ontinue)"..GREEN_CARET.."continue execution\n"
      .. COLOR_BLUE.."  b"..COLOR_YELLOW.."(reak) "..COLOR_BLUE.."[[file:]function]"..GREEN_CARET.."set breakpoint at specified function\n"
      .. COLOR_BLUE.."  d"..COLOR_YELLOW.."(elete) "..COLOR_BLUE.."[index]"..GREEN_CARET.."remove breakpoint\n"
      .. COLOR_BLUE.."  s"..COLOR_YELLOW.."(tep)"..GREEN_CARET.."step forward by one line (into functions)\n"
      .. COLOR_BLUE.."  n"..COLOR_YELLOW.."(ext)"..GREEN_CARET.."step forward by one line (skipping over functions)\n"
      .. COLOR_BLUE.."  f"..COLOR_YELLOW.."(inish)"..GREEN_CARET.."step forward until exiting the current function\n"
      .. COLOR_BLUE.."  u"..COLOR_YELLOW.."(p)"..GREEN_CARET.."move up the stack by one frame\n"
      .. COLOR_BLUE.."  d"..COLOR_YELLOW.."(own)"..GREEN_CARET.."move down the stack by one frame\n"
      .. COLOR_BLUE.."  w"..COLOR_YELLOW.."(here) "..COLOR_BLUE.."[line count]"..GREEN_CARET.."print source code around the current line\n"
      .. COLOR_BLUE.."  e"..COLOR_YELLOW.."(val) "..COLOR_BLUE.."[statement]"..GREEN_CARET.."execute the statement\n"
      .. COLOR_BLUE.."  p"..COLOR_YELLOW.."(rint) "..COLOR_BLUE.."[expression]"..GREEN_CARET.."execute the expression and print the result\n"
      .. COLOR_BLUE.."  t"..COLOR_YELLOW.."(race)"..GREEN_CARET.."print the stack trace\n"
      .. COLOR_BLUE.."  l"..COLOR_YELLOW.."(ocals)"..GREEN_CARET.."print the function arguments, locals and upvalues.\n"
      .. COLOR_BLUE.."  h"..COLOR_YELLOW.."(elp)"..GREEN_CARET.."print this message\n"
      .. COLOR_BLUE.."  q"..COLOR_YELLOW.."(uit)"..GREEN_CARET.."halt execution\n"
   )
   return false
end

local last_cmd = false
local abc = 0

local function in_array(tab, val)
    for index, value in ipairs(tab) do
        if value == val then
            return true
        end
    end

    return false
end

local function split(inputstr, sep)
   if sep == nil then
          sep = "%s"
   end
   local t={}
   for str in string.gmatch(inputstr, "([^"..sep.."]+)") do
          table.insert(t, str)
   end
   return t
end

local function debug_hook(offset, reason)
   local function trace (event, line)
      if event == "line" then
         return
      end

      local s = debug.getinfo(2)

      if #s.namewhat > 0 then
         local i = split(s.short_src, "/")
         local long_name = i[#i]..":"..s.name

         if in_array(break_funcs, long_name) or in_array(break_funcs, s.name) then
            offset = offset - 1
            repl(reason)
         end
      end
   end
   return trace
end
debug.sethook(debug_hook(0), "crl")

local function cmd_continue()

   return true, debug_hook
end

local commands = {
   ["^c$"] = cmd_continue,
   ["^b%s+(.*)$"] = cmd_break,
   ["^d%s+(%d*)$"] = cmd_delete,
   ["^s$"] = cmd_step,
   ["^n$"] = cmd_next,
   ["^f$"] = cmd_finish,
   ["^p%s+(.*)$"] = cmd_print,
   ["^e%s+(.*)$"] = cmd_eval,
   ["^u$"] = cmd_up,
   ["^d$"] = cmd_down,
   ["^w%s*(%d*)$"] = cmd_where,
   ["^t$"] = cmd_trace,
   ["^l$"] = cmd_locals,
   ["^h$"] = cmd_help,
   ["^q$"] = function() dbg.exit(0); return true end,
}

local function match_command(line)
   for pat, func in pairs(commands) do
      -- Return the matching command and capture argument.
      if line:find(pat) then return func, line:match(pat) end
   end
end

-- Run a command line
-- Returns true if the REPL should exit and the hook function factory
local function run_command(line)
   -- GDB/LLDB exit on ctrl-d
   if line == nil then dbg.exit(1); return true end
   
   -- Re-execute the last command if you press return.
   if line == "" then line = last_cmd or "h" end
   
   local command, command_arg = match_command(line)
   if command then
      last_cmd = line
      -- unpack({...}) prevents tail call elimination so the stack frame indices are predictable.
      return unpack({command(command_arg)})
   elseif dbg.auto_eval then
      return unpack({cmd_eval(line)})
   else
      dbg_writeln(COLOR_RED.."Error:"..COLOR_RESET.." command '%s' not recognized.\nType 'h' and press return for a command list.", line)
      return false
   end
end

repl = function(reason)
   -- Skip frames without source info.
   while not frame_has_line(debug.getinfo(stack_inspect_offset + CMD_STACK_LEVEL - 3)) do
      stack_inspect_offset = stack_inspect_offset + 1
   end
   
   local info = debug.getinfo(stack_inspect_offset + CMD_STACK_LEVEL - 3)
   reason = reason and (COLOR_YELLOW.."break via "..COLOR_RED..reason..GREEN_CARET) or ""
   dbg_writeln(reason..format_stack_frame_info(info))
   
   if tonumber(dbg.auto_where) then where(info, dbg.auto_where) end
   
   repeat
      local success, done, hook = pcall(run_command, dbg.read(COLOR_RED.."debugger.lua> "..COLOR_RESET))
      if success then
         debug.sethook(hook and hook(0), "crl")
      else
         local message = COLOR_RED.."INTERNAL DEBUGGER.LUA ERROR. ABORTING\n:"..COLOR_RESET.." "..done
         dbg_writeln(message)
         error(message)
      end
   until done
end

-- Make the debugger object callable like a function.
dbg = setmetatable({}, {
   __call = function(_, condition, top_offset, source)
      if condition then return end
      
      top_offset = (top_offset or 0)
      stack_inspect_offset = top_offset
      stack_top = top_offset
      
      debug.sethook(hook_next(1, source or "dbg()"), "crl")
      return
   end,
})

-- Expose the debugger's IO functions.
dbg.read = dbg_read
dbg.write = dbg_write
dbg.shorten_path = function (path) return path end
dbg.exit = function(err) os.exit(err) end

dbg.writeln = dbg_writeln

dbg.pretty_depth = 3
dbg.pretty = pretty
dbg.pp = function(value, depth) dbg_writeln(pretty(value, depth)) end

dbg.auto_where = false
dbg.auto_eval = false

local lua_error, lua_assert = error, assert

-- Works like error(), but invokes the debugger.
function dbg.error(err, level)
   level = level or 1
   dbg_writeln(COLOR_RED.."ERROR: "..COLOR_RESET..pretty(err))
   dbg(false, level, "dbg.error()")
   
   lua_error(err, level)
end

-- Works like assert(), but invokes the debugger on a failure.
function dbg.assert(condition, message)
   if not condition then
      dbg_writeln(COLOR_RED.."ERROR:"..COLOR_RESET..message)
      dbg(false, 1, "dbg.assert()")
   end
   
   return lua_assert(condition, message)
end

-- Works like pcall(), but invokes the debugger on an error.
function dbg.call(f, ...)
   return xpcall(f, function(err)
      dbg_writeln(COLOR_RED.."ERROR: "..COLOR_RESET..pretty(err))
      dbg(false, 1, "dbg.call()")
      
      return err
   end, ...)
end

-- Error message handler that can be used with lua_pcall().
function dbg.msgh(...)
   if debug.getinfo(2) then
      dbg_writeln(COLOR_RED.."ERROR: "..COLOR_RESET..pretty(...))
      dbg(false, 1, "dbg.msgh()")
   else
      dbg_writeln(COLOR_RED.."debugger.lua: "..COLOR_RESET.."Error did not occur in Lua code. Execution will continue after dbg_pcall().")
   end
   
   return ...
end

-- Conditionally enable color support.
local color_maybe_supported = (os.getenv("TERM") and os.getenv("TERM") ~= "dumb")
if color_maybe_supported and not os.getenv("DBG_NOCOLOR") then
   COLOR_GRAY = string.char(27) .. "[90m"
   COLOR_RED = string.char(27) .. "[91m"
   COLOR_BLUE = string.char(27) .. "[94m"
   COLOR_YELLOW = string.char(27) .. "[33m"
   COLOR_RESET = string.char(27) .. "[0m"
   GREEN_CARET = string.char(27) .. "[92m => "..COLOR_RESET
end

dbg_writeln(COLOR_YELLOW.."debugger.lua: "..COLOR_RESET.."Loaded for ".._VERSION.." (Lite-XL)")

command.add(nil, {
   ["debugger:break"] = function()
      dbg()
   end,
})