profiler.lua

--[[
  A low-overhead minimal lua profiler.

  It requires cooperation from the lua interpreter itself, which we patch, and then
  compile a custom pandoc binary.
  
  In other words, this is not meant to be used by regular quarto users.
]]

local getTime = os.clock
local category = "unknown"
local module = {}
local outputfile
local stack_count = 0

-- don't colect coverage for this module
-- luacov: disable
local onDebugHook = function(hookType, line)
  if hookType ~= "alarm" then
    print("Internal Error - Unexpected hook type in debug hook: " .. hookType)
    print("For Quarto profiling to work, you need to run a patched version of Pandoc.")
    print("This feature is currently only meant to be used by Quarto developers.")
    os.exit(1)
  end
  local no = 2
  local information = debug.getinfo(no, "nS")
  local now = os.clock()
  while information ~= nil do
    local source = information.source or "unknown"
    local name = information.name or "anon"
    if source:sub(1, 1) == "@" then
      outputfile:write(name, " ", source, " ", information.linedefined, "\n")
    else
      outputfile:write(name, " ", "<inline>", " ", 0, "\n")
    end
    no = no + 1
    information = debug.getinfo(no, "nS")
  end
  outputfile:write(stack_count, " ", now, " ", category, " ", line, "\n")
  stack_count = stack_count + 1
end

function module.setcategory(c)
  category = c
end

function module.start(filename, ms)
  outputfile = io.open(filename, "a")
  if outputfile == nil then
    error("Could not open " .. filename .. " for writing")
    return
  end
  debug.sethook(onDebugHook, "t", ms or 5) -- NB: "t" debugging only exists in our patched Lua interpreter/pandoc binary!
end

function module.stop()
  debug.sethook()
  outputfile:close()
end
-- luacov: enable

return module