Papyrus not generating in savanna shores and jungle biomes on v7 map generator

[Priestessofspiders]

Running Luanti version 5.10.0, latest version of minetest game.

Have checked savanna shore biomes and jungle biomes for several hours in search of naturally generating papyrus, searched for several thousand blocks in multiple directions, have been unable to locate any. Problem exists in the v7 map generator, multiple different seeds have been tested.

[MagnusMWW]

Also noticed this. It seems that the water-level is one unit too high (or the shoreline is one unit too low). You can observe it by flying into newly generated areas and see that grass is just under the waterlevel and slowly turning to dirt.

[benotten]

Noticed this since yesterday. Current work around that I have found is to turn on advanced settings, and set water level to 2 in mapgen. I would surmise this has to do with a value being off for either terrain generation, or water generation. The workaround works, however the papyrus is spawning on top of the water with only water under it, and not on savanna, or jungle blocks. Papyrus still generates in v6 as intended, just not other versions.

[appgurueu]

We can do effectively the equivalent of the workaround you mention in code by fixing y_min and y_max (though I suppose these should be made dependent on the water level setting):

diff --git a/mods/default/mapgen.lua b/mods/default/mapgen.lua
index cc5b9bf..a77a286 100644
--- a/mods/default/mapgen.lua
+++ b/mods/default/mapgen.lua
@@ -2159,8 +2159,8 @@ function default.register_decorations()
 			persist = 0.7
 		},
 		biomes = {"rainforest_swamp"},
-		y_max = 0,
-		y_min = 0,
+		y_max = -1,
+		y_min = -1,
 		schematic = minetest.get_modpath("default") .. "/schematics/papyrus_on_dirt.mts",
 	})
 
@@ -2180,8 +2180,8 @@ function default.register_decorations()
 			persist = 0.7
 		},
 		biomes = {"savanna_shore"},
-		y_max = 0,
-		y_min = 0,
+		y_max = -1,
+		y_min = -1,
 		schematic = minetest.get_modpath("default") ..
 			"/schematics/papyrus_on_dry_dirt.mts",
 	})

but this suffers from the same issue: There is a gap between papyrus and dirt.