schedule-table: wrong real/thoretical margin computation when arrival time is set on a waypoint

[Castavo]

What happened?

The first train is set with a margin of 5%.
When I duplicate the train, and set an arrival time on one of the stops at the time at which it arrives naturally with the margin, then the margin computations are off

Enregistrement.de.l.ecran.2025-01-24.125205.mp4

What did you expect to happen?

I expect the margins to be okay (theoretical and real should match in this case)

How can we reproduce it (as minimally and precisely as possible)?

1. Create a first train with some margin
2. Add an arrival time on a waypoint, at the time it is supposed to cross this waypoint with the margin
3. Witness the discrepancy

You can use this pre-made example too

On which environments the bug occurs?

Recette (SNCF)

On which browser the bug occurs?

Firefox

OSRD version (top right corner Account button > Informations)

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[eckter]

The issue is that we add margin ranges at every scheduled point, including when it's very close to the original result. But we've always had issues when it comes to ordering the margin ranges and the constraints we set on transitions. In such a case we'd need to simulate them in chronological order, but we wouldn't do that if the point is close to the origin.

This won't be fixed until the future large refactoring of running time simulations. Which sadly isn't planned soon and has been postponed for quite a while.

The best I could do for a partial fix would be to ignore scheduled points if they are all close to the initial result. But that's a very specific case and it wouldn't fix the issue, just kind of hide it.