[raiguard][2.0.15] Underground pipe ghost not pairing correctly, results in mixed and swapped fluids

[Linsanga]

Repro steps (matching pictures):

Step 1. Load attached UndergroundPipeDemo.zip:

1.png (1.22 MiB) Viewed 562 times

Step 2. Copy-paste the pipe layout on the right to the left:

2.png (1.22 MiB) Viewed 562 times

Step 3. Watch as your bots build the lower underground pipe first, since you are closer to it:

3.png (1.22 MiB) Viewed 562 times

Step 4. Watch your bots build the rest of the pipes, and the fluids swap around in the two pipe systems that should not have connected:

4.png (1.21 MiB) Viewed 562 times

What happened: Water ends up in the bottom pipe system, and lubricant ends up the top system. This consistently happens every time after loading and copy-pasting. Interestingly in step 3 they are not mixed, so it looks like the ghost is correctly blocking the connection to a degree. Only in step 4 do they mix.
What I expected: The top pipe system shouldn't connect to the bottom pipe system, since the ghost is blocking it. Water stays in the top pipes, lubricant stays in the bottom pipes.

[Linsanga]

With the changes to fluid systems where mixed fluids are deleted, this is still a bug, but the results are a little different. In picture 4, instead of seeing mixed fluids, I see water in both pipes. Expected: lube stays in the bottom pipe, water stays in the top pipe.

[raiguard]

I have a plan for fixing this, but it will not come soon - it will require some pretty hefty changes to how fluid segments are merged.

[boskid]

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