I can befriend hallucinatory NPCs

[hexagonrecursion]

Describe the bug

It is possible to hallucinate an NPC. You can even talk it her. You can even ask him to be your friend. All sorts of shenanigans become possible once you have an imaginary friend. Right, Alice? All sorts of shenanigans. She agrees disagrees refuses to comment.

Steps to reproduce

1. Hallucinate an NPC. This may take a while. I do not know how to make this quick.
2. (optional) save, quit and backup your world
3. Befriend the NPC. This may take a few tries. Note: I did not use debug mind control out of concern that it might interfere with the experiment
4. Profit

Things you can do once you have an imaginary friend include:

1. Bump into your friend and select "Trade" in the menu. Note: trading through the talk menu appears to be disabled for hallucinations.
2. Sort the armor of your imaginary friend
3. Talk -> "there's something I want you to do" -> "drop off any items you are not using"
4. Ask your friend to train you
5. Likely many, many more

1 and 2 allow transfer of items both to and from your imaginary friend. 3 is one-directional.

Expected behavior

The game should not allow you to befriend a hallucination.

Screenshots

No response

Versions and configuration

• OS: Linux
  • OS Version: LSB Version: :core-4.1-amd64:core-4.1-noarch; Distributor ID: Fedora; Description: Fedora release 34 (Thirty Four); Release: 34; Codename: ThirtyFour;
• Game Version: 0.F-4523-g00a57e1f7d [64-bit]
• Graphics Version: Tiles
• Game Language: English [en]
• Mods loaded: [
  Dark Days Ahead [dda],
  Disable NPC Needs [no_npc_food],
  No Fungal Growth [no_fungal_growth],
  Bionic Professions [package_bionic_professions]
  ]

Additional context

Originally reported here #53243 (comment) #53243 (comment) #53243 (comment)

I am merging this all into one bug because I expect one fix. If you instead choose to audit every possible interaction one could have with an allied NPC and make it hallucination-aware (much more code and many more bugs for little profit IMHO; Alice approves though, but she is biased), you should split this bug into several.

[foul-fortune-feline]

I feel like maybe you should be able to befriend a hallucination, but they shouldn't give you physical objects or train you in anything you don't know (Maybe they could train up practical skill if you have theoretical skill tho)

[hexagonrecursion]

Me and Alice both agree that imaginary friends are awesome. What is not awesome, however, is that there are probably hundreds of places in the code that would need to be hallucination-aware - there are many mechanics that involve allied NPC interaction. This is also prone to regressions - when code changes or when new mechanics are added. Disallowing this state entirely is much easier.

[Inglonias]

We already have many places in the code that are hallucination aware regarding NPCs. This was added as a feature, rather than a bug.

[ChrisGarrett23]

Personally I love that this exists and would love to see any items you give them just get dropped on the floor.

This is a neat area/thought for Magiclysm, some imaginary friends could actually be tricky and steal what you give or friendly and act like a tiny pocket dimension for items.

[Fris0uman]

Befriending hallucinations is definitly intended #28157
Trading and getting items from them is not though

[hexagonrecursion]

Ok. I'll split this then

[hexagonrecursion]

I'll wait until a build containing #54307 is available

[hexagonrecursion]

The examine -> trade exploit is fixed

• OS: Linux
  • OS Version: LSB Version: :core-4.1-amd64:core-4.1-noarch; Distributor ID: Fedora; Description: Fedora release 34 (Thirty Four); Release: 34; Codename: ThirtyFour;
• Game Version: c8a49e1 [64-bit]
• Graphics Version: Tiles
• Game Language: English [en]
• Mods loaded: [
  Dark Days Ahead [dda],
  Disable NPC Needs [no_npc_food],
  Graphical Overmap [Graphical_Overmap]
  ]

[hexagonrecursion]

Above are several examples of shenanigans. TLDR: there are many mechanics specific to NPC followers. Every single one needs to be audited to correctly handle hallucinations. What is worse: we now have to know about this edge case and remember to handle it correctly any time we add a new follower-related mechanic.