debug.traceback failed on anonymous function

TypeScriptToLua/src/lualib/SourceMapTraceBack.ts

Line 52 in 1ed3b4d

let [result] = string.gsub(trace, "(%S+)%.lua:(%d+)", (file, line) =>

When anonymous functions are included in TS code, stack.traceback printing doesn't work exactly as expected, such as in the form SOME_PATH\dist\main.ts:43: in function <SOME_PATH\dist\main.lua:65>.
This is because the "<" escapes as a non-whitespace character matching the %S, causing it to be considered part of the path.

On Windows, you can quickly fix this by changing the pattern to ([^%s<]+)%.lua:(%d+).
This isn't the most elegant fix, considering that "<" can be part of a filename on Unix-like systems.

Additional, my guess is that if there are spaces in the entire path, it may also cause unexpected behavior because of %S.

However, collecting the paths to build a regular expression can be quite risky.
Do you have any suggestions?

fix `debug.traceback` failing on anonymous function (TypeScriptToLua#…

Which Lua runtime are you using? In my quick check I don't see the <> notation used in Lua 5.3 or 5.4.

And do you have some example code that actually produces the problem? I've been using this to test:

function bla()
  local f = function()
    error("hi")
  end
  f()
end

bla()

test: add regression test for anonymous function traceback mapping (T…

@Perryvw

Hi @Perryvw, I've added a regression test for this in PR #1666.

If you'd like a quick way to reproduce the issue, nested IIFEs work well — the anonymous function definitions show up as <file.lua:N> in debug.traceback(), and those lines do have sourcemap entries:

(() => {
    (() => {
        print(debug.traceback());
    })();
})();

Hope that helps!

test: address review feedback for anonymous function traceback test (T…

fix `debug.traceback` failing on anonymous function (#1665) (#1666)

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debug.traceback failed on anonymous function #1665

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Perryvw commented on Nov 2, 2025

ChouUn commented on Feb 27, 2026

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