[2.0.71] Crash during migration of Bulk Rail Loader and legacy-straight-rail (Rail::makeRealRailConnection)

[Sander20011]

I wanted to migrate my modded savegame to 2.0 since all the mods I used are ported to 2.0 but when trying to load a save containing Bulk Rail Loaders to the new version of Bulk Rail Loaders it crashes.
I suspect it has something to do with the rail segments the entity places to connect the rails, but I am unable to test this myself.

[ThePiachu]

I also encountered this bug migrating my save to 2.0.77.

factorio-current.log

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[robot256]

I've seen this in the past when trying to migrate a pre-2.0 "straight-rail" directly to a 2.0 "straight-rail". The order of the connection points is different so it doesn't work. The solution is to migrate the old rails to a "legacy-straight-rail" prototype, and either leave them like that or use scripts to replace them with a new 2.0 "straight-rail" entity later.

It's very likely this is a problem in one or more of the Bulk Rail Loaders forks, but I haven't checked.

[Rseding91]

Looking into this; I don't think this is fixable. The entire train and rail system is setup to assume the rails *don't change* once created and this is doing exactly that. In the best case - the rails change and any trains on them get deleted. In the worse case it crashes like it is now.