Confilct packages Error in ink! smart contract

Question

I'm trying to build some ink! contract code (this one) but I got this error:

error: There are multiple `parity-scale-codec` packages in your project, and the specification `parity-scale-codec` is ambiguous.
Please re-run this command with `-p <spec>` where `<spec>` is one of the following:
  parity-scale-codec:2.3.1
  parity-scale-codec:3.1.0

This is my cargo.toml file:

[package]
name = "nft"
version = "0.1.0"
authors = ["Nick Shulhin (Polk4.net) <[email protected]>"]
edition = "2018"

[dependencies]
ink_primitives = { version = "=3.0.0-rc3", default-features = false }
ink_metadata = { version = "=3.0.0-rc3", default-features = false, features = ["derive"], optional = true }
ink_env = { version = "=3.0.0-rc3", default-features = false }
ink_storage = { version = "=3.0.0-rc3", default-features = false }
ink_lang = { version = "=3.0.0-rc3", default-features = false }

scale-info = { version = "2", default-features = false, features = ["derive"], optional = true }
scale = { package = "parity-scale-codec", version = "3", default-features = false, features = ["derive", "full"] }

[lib]
name = "nft"
path = "lib.rs"
crate-type = [
    # Used for normal contract Wasm blobs.
    "cdylib",
]

[features]
default = ["std"]
std = [
    "ink_metadata/std",
    "ink_env/std",
    "ink_storage/std",
    "ink_primitives/std",
    "scale/std",
    "scale-info/std",
]
ink-as-dependency = []

Answer 1

To answer your question - it's because the versions of your ink dependencies are dependent on different versions of your scale dependencies.

As @P.Ossun mentioned, with rc-9 it will work with your scale dependencies, I'm not sure you will even be able to build it with rc-3 if you even adjusted the scale dependencies.

If you will use rc-9, then you will also need to change the version of your package to 2021.