akkartik/template-live - Change 23BYUXSYSYNIVNZI5YN3UGW2J4RVJY2N3OYT2BY7UQ52ZZDH6ZOQC

bugfix: show error message on infinite recursion

Scenario: on.draw = function() f() end

f = function() f() end

Before this commit, the app would crash without error.

Summary of error handling in Lua and LÖVE:

errors in the xpcall handler silently crash the program. I always knew this. Error handlers are hard, because they must never throw an error no matter what situation they find themselves in. But it's impossible to know in advance all the situations they find themselves in.
LÖVE has some secret sauce that causes errors in the xpcall handler (NOT love.errorhandler, which I'm not using lately) to only interrupt the current frame, and resume on the next frame. They don't crash the entire program.
I've also seen some signs that running out of stack destabilizes things. I found a string that would throw an error any time I tried to use it. So it seems a good idea to minimize work in error handlers on stack overflow. Prioritize getting some error message out on stack overflow.

Created by akkartik on March 1, 2025

23BYUXSYSYNIVNZI5YN3UGW2J4RVJY2N3OYT2BY7UQ52ZZDH6ZOQC

Dependencies

In channels

main

Change contents

Replacement in main.lua at line 465 [4.4]

B:BD[3.1239] → [2.0:171]

  local callstack = debug.traceback('', --[[stack frame]]2)
  local cleaned_up_error = 'Error: ' .. cleaned_up_frame(tostring(err))..'\n'..cleaned_up_callstack(callstack)

[3.1239]

[2.171]

  local cleaned_up_error = err
  if not err:match('stack overflow') then
    local callstack = debug.traceback('', --[[stack frame]]2)
    cleaned_up_error = 'Error: ' .. cleaned_up_frame(tostring(err))..'\n'..cleaned_up_callstack(callstack)
  else
    -- call only primitive functions when we're out of stack space
  end

Replacement in main.lua at line 504 [4.4]

B:BD[2.1050] → [2.1050:1100]

  return cleaned_up_filename(filename)..':'..rest

[2.1050]

[2.1100]

  if filename then
    return cleaned_up_filename(filename)..':'..rest
  else
    return line
  end

Replacement in README.md at line 33 [6.4663627]

B:BD[5.8] → [5.8:259]

∅:D[5.259] → [6.4664492:4664493]

B:BD[6.4664492] → [6.4664492:4664493]

B:BD[5.738] → [5.738:1123]

* Don't start the driver app while multiple freewheeling apps are running. If
  you have a driver app running with one app, shut it down before you switch
  apps. Just always open the app and then the driver. If you close the app,
  close the driver.
* Don't give up your other tools just yet. It's easy to make a mistake that
  the app doesn't recover from when you fix it. Try restarting the app, and if
  it still doesn't work, perhaps you need to fix the initial load. This isn't
  yet a tool you can keep open for months on end. (And I'm ambivalent about
  making it such a tool since your programs might stop working for others.)

[5.8]

[5.1123]

* This approach puts one top-level definition per file, and so obscures the
  order in which definitions are loaded. In particular, initializing a global
  table to contain other global definitions will fail if you originally
  authored the other global definitions after the table.

Replacement in README.md at line 38 [6.4663627]

B:BD[5.1124] → [5.1124:1507]

* I still see driver and the app being driven occasionally crash. When I do I
  try to make things more robust. If you do you'll quite possibly crash again
  if you try to restart. In such a situation you'll have to bump down to
  editing the underlying version files by other means. See [representation.md](representation.md)
  for details of the underlying representation on disk.

[5.1124]

[6.4664758]

  I never initialize global tables with other definitions. That kind of thing
  happens in `on.initialize` (akin to `love.load`; see reference.md) or
  `on.code_change`.

Replacement in README.md at line 42 [6.4663627]

B:BD[6.4664759] → [5.1508:1684]

* Given the above issues, both this driver and its client freewheeling app
  benefit from being launched in terminal windows rather than by being clicked
  on in a desktop OS.

[6.4664759]

[5.1684]

* Don't start the driver app while multiple freewheeling apps are running. If
  you have a driver app running with one app, shut it down before you switch
  apps.