BTreeMap on Anchor ^0.29.0 stopped working?

Question

Before anchor 0.29.0, BTreeMaps where working correctly in my programs, but now that I'm moving to ^0.29.0 I'm getting the following errors for every BTreeMap when I'm building my program.

no associated item named `__anchor_private_insert_idl_defined` found for struct `std::collections::BTreeMap` in the current scope

no associated item named `__anchor_private_gen_idl_type` found for struct `std::collections::BTreeMap` in the current scope

no associated item named `__anchor_private_full_path` found for struct `std::collections::BTreeMap` in the current scope

#[derive(AnchorSerialize, AnchorDeserialize, PartialEq, Eq, Debug, Clone)]
      |          ^^^^^^^^^^^^^^^ associated item not found in `BTreeMap<u64, u8>`

note: this error originates in the derive macro `AnchorSerialize` (in Nightly builds, run with -Z macro-backtrace for more info)

How should I be dealing with this? Any idea what's going on?

Thanks in advance.

Answer 1

This looks like a known issue: https://github.com/coral-xyz/anchor/issues/2729#issuecomment-2155844009

Copying from the comment:

The reason for not supporting BTreeMap (or any of the map data structures) has to do with the nature of Solana programming. Beginners usually try to use a global map for everything (especially eth people), which is almost always a worse choice than using PDAs