Requiring assistance with locating grass-spread code in 1.20.12

Nuopea · July 17, 2025

Hey hey~

I want to change the grass-spread behaviou (on soil specifically), but can't locate the relevant code.
As it stands, grass doesn't seem to spread in a particular area in my save-file,
which I am guessing is due to a combination of inappropraite (lacking) light / sky-exposure and inappropraite biome.
I don't particularly care which biome it is, as I'd like the grass to be able to spread everywhere, under all conditions (at least in temperatures above 0), including in 0 light environments.

For elaboration, I am trying to convert a decently nice mountain, which appears to be a colder biome, into a pretty forest with a dense canopy.
To that end I have planted trees which cover a large portion of sky, and placed a fair amount of medium fertility soil.
As after several hours (~4 to 6) the grass had not spread from low fertility soil with grass, which spawned naturally in the same biome,
I place some low fertility soil right next to it as well to see if that would function. It did not (after another ~4 to 6 hours).
In both instances, artifical light surces (a lantern and an oil lamp) were placed next to the natrual grass blocks as well.
Then I placed a block of medium fertility soil with grass, gained through the creative menu, in the area with already placed medium fertility soil, ensuring it was exposed to the sky. The grass appears to have disappeared, when exactly I do not know.

Any assistance/direction with this would be appreciated.

PS.: Apologies if the post in the wrong section or addressed incorrectly, this is the first time posting on a forum like this.