Support for zero-setup object method profiling?

[nietaki]

This is a vague proposal / food for thought / example of how I use AppleCake. It might not make sense to add this functionality to AppleCake itself, but I would like to at least share what I did - maybe it's going to be useful to somebody else.

---

Ever since I started using AppleCake more extensively, I realised it became a bit of a pain to wrangle the profile objects and to make sure the methods on different objects weren't re-using calls of the same method on different objects or recursive calls on the same method.

I realise the OO approach isn't a first-class thing in Lua and there's many ways to get it (I'm using middleclass right now), but it was an important enough use-case for me that I built up an AppleCake utility mixin to handle that.

Here's how I use it in real code:

ShaderStructArray = class('ShaderStructArray')

-- object fields to include in the profile args
ProfiledObject.includeIn(ShaderStructArray, {fields = {'name'}})

-- example method
function ShaderStructArray:markUnchanged()
  self:trace()
  for _, struct in ipairs(self._elements) do
    struct:markUnchanged()
  end
  self:untrace()
end

This allows me to easily get more complicated traces like this one:

There's probably a better and more generic way of implementing it, but here's the code for the ProfiledObject mixin (you'll find some chunks of it stolen from the AppleCake implementation):

local function _methodNameAndPath(self)
  local className = self.class.name or 'UnknownClass'
  local name = 'unknownName'
  local path = 'unknownPath'
  local info = debug.getinfo(3, "fnS")
  local line = ""
  if info then
    if info.name then
      name = info.name
    elseif info.func then -- Attempt to create a name from memory address
      name = tostring(info.func):sub(10)
    else
      error("Could not generate name for this function")
    end
    if info.short_src then
      line = (info.linedefined and "#"..info.linedefined or line)
      path = info.short_src..line
    end
  end
  -- return className .. '.' .. name .. '[' .. line .. ']', path
  return string.format('%s.%s[%s]', className, name, line), path
end

local profilesFieldName = '_objectProfiles'

local function _profiles(self)
  local profiles = rawget(self, profilesFieldName)
  if not profiles then
    profiles = {}
    rawset(self, profilesFieldName, profiles)
  end
  return profiles
end

local function buildArgs(self, args)
  args = args or {}
  if self.class.profiledFieldNames then
    for _, fieldName in ipairs(self.class.profiledFieldNames) do
      args[fieldName] = rawget(self, fieldName)
    end
  end
  return args
end

local function _profileName(baseName, recursionDepth)
  if recursionDepth and recursionDepth > 0 then
    -- baseName ..
    return baseName .. '_level_' .. tostring(recursionDepth)
  else
    return baseName
  end
end

local function startProfile(self, args, recursionDepth)
  local name, path = _methodNameAndPath(self)
  args = buildArgs(self, args)
  -- print('method', _methodNameAndPath(self))
  args.path = path

  local profileName = _profileName(name, recursionDepth)
  local profile = _profiles(self)[profileName]
  profile = AppleCake.profile(name, args, profile)
  _profiles(self)[profileName] = profile
end

local function mark(self, name, subname)
  name = tostring(name)
  if subname then
    AppleCake.mark(name .. ' -> ' .. tostring(subname))
  else
    AppleCake.mark(name)
  end
end

local function stopProfile(self, recursionDepth)
  local profileName, _ = _methodNameAndPath(self)
  profileName = _profileName(profileName, recursionDepth)
  local profile = _profiles(self)[profileName]
  profile:stop()
end


ProfiledObject = {
  startProfile = startProfile,
  stopProfile = stopProfile,
  trace = startProfile,
  untrace = stopProfile,
  mark = mark,
}

ProfiledObject.includeIn = function(klass, opts)
  klass.profiledFieldNames = opts.fields or {}
  klass:include(ProfiledObject)
end

AppleCake itself is impressively low-overhead, so I tried to keep the code light here and to have it not do too much unnecessary work.

---

Feel free to close the issue as I'm not sure it's really actionable, but again - I thought it was worth sharing