I have an old mod (Magic Wands) that I'm updating and it allows the user to configure a list of blocks that can be affected by the mod item.  Comparing which blocks should be affected would fit ideally with a tag, but I haven't been able to figure out a way to update a tag within the program--that is, load a list of blocks (or other tags) from the config file and create a new tag from them.

Is it possible to create and/or modify a tag after loading is complete?  If so, how?

Thanks!

use a config, note that you can not read/write a block directly from/into the config, you should use the registry name

write into a file at runtime which is generate by vanilla is a good idea?

but tags are file based, or can we edit them on runtime?
iirc the file tag is final

Edited August 13, 20214 yr by Luis_ST

Okay, looks like I wasn't very clear in my first post.

Here's a simplified version of what I'm aiming for:

I have a custom item, a magic wand.  The player hits a block with the wand and depending on what type of block it is (e.g. minecraft:dirt), it disappears.  Or it doesn't disappear (e.g. minecraft:obisidian).

I want the player, using a config file (e.g. %appdata%\.minecraft\config\magicwands.cfg  or  magicwands-client.toml in the newer versions), to be able to specify a list of which blocks disappear, e.g.:

  disappearingblocks = minecraft:dirt,minecraft:sand,minecraft:gravel,minecraft:logs

When Minecraft loads, my mod reads that list from the config file, builds a custom tag that contains those blocks/tags.  Then, when the player hits a block with the wand item, the program compares the blockstate with the "disappearingblocks" tag, and then either changes the block to air or does nothing.

If the player, say, doesn't want the wand to affect gravel, I want them to be able to edit that config file and remove it from the list.

The old version of the mod, before tags existed, just used strings to compare the block's unlocalized name to the list of block names read as a string from the config file.

The wand item cannot be coded using data packs, it's way too complex (it actually does a lot more than the simplified description above).

The question is, can I create the "disappearingblocks" tag and add blocks/tags to it during the Minecraft "setup" or "doClientSetup" phase?  Once it's past the setup phase, it doesn't need to change.
 

49 minutes ago, electro1574 said:

If the player, say, doesn't want the wand to affect gravel, I want them to be able to edit that config file and remove it from the list.

The wand item cannot be coded using data packs, it's way too complex (it actually does a lot more than the simplified description above).

You don't know how data packs work, do you?

The tag json files are config files.

After realizing I didn't know much about datapacks (thanks), and a bunch of reading, the one thing I don't get about datapacks is, if they're used within a java mod, how is the player supposed to modify the datapack to their liking?  Without unzipping the JAR and modifying the datapack inside it, that is.

Is there a way to get a java mod to write out a datapack to a world's save folder?  Or would it have to be distributed as a java mod plus a separate datapack (which overrides the in-mod datapack) that the player installs if they want to modify the settings?