remove assertion of direction matching between begin/end dir nodes

[Udi-Fogiel]

LuaTeX does not really care about the direction of an enddir node, it only consider it as a flag to pop the current dir, and restore the old one (see pdflistout.c).

I don't think luaotfload should be more restrictive then the engine.

[zauguin]

I somewhat disagree. If the direction here does not match the nodes are in an unexpected state and we might not recover correctly. Any case where this occurs at the very least would have to be separately checked.

What is the motivation for this change?

[Udi-Fogiel]

If the direction here does not match the nodes are in an unexpected state and we might not recover correctly.

Hmmm can you elaborate? As far as I can tell LuaTeX is a bit more permissive about dir nodes structure, so what is an expected state?

What is the motivation for this change?

Not a real motivation, just noticed it when playing with things and thought that this check is a bit too harsh.

But thinking about it more, it is unclear from LuaTeX's source what should happen. The output to pdf code does not check the direction of enddir nodes, but the line breaker somewhat cares about them... so there seems to be some inconsistency about it even in the source code.

It is somewhat puzzling why enddir nodes have direction in the first place, if it does not affect anything.

Any case where this occurs at the very least would have to be separately checked.

There are cases, even without lua, where there are unbalanced dir nodes, though maybe they should be considered a bug. For example the undocumented \fixupboxesmode fix one of these cases, see https://mailman.ntg.nl/archives/list/dev-luatex@ntg.nl/thread/2PZX3W7322ZZZM4YB3WZVTO5EF4YKXHY/ for another.