magic-import

Improved version of auto-import

The magic_import::magic!(); macro expands to whatever use statements you need to make the rest of the code compile. It is not intelligent enough to figure out which is the correct import in cases of ambiguity, but it does have some rules to get good imports, whereas auto-import would just import the first available option. If none of the rules could find out which is the best import, it will pick one at random

The stable feature flag will work on stable, but only once per crate. That's the behaviour from auto-import, but magic-import's default is to work once per file, and that uses the proc_macro_span unstable feature. If you want to use this more than once per crate, but also want to support stable toolchain, consider nightly-crimes, a really cool package that might help you with that.

https://twitter.com/Terrain222/status/1528076303890624515

Example

// it even resolves macros and prelude items fine
#![no_implicit_prelude]

// magic_import does not try to resolve which crates to import
// these would normally be included by prelude
extern crate magic_import;
extern crate std;
// extern crate core; // for prefer_core

magic_import::magic!();

fn main() {
    let _ = BTreeMap::<File, PathBuf>::new();
    if let Ok(i) = i32::from_str("123") {
        print!("{i}");
    } else {
        unreachable!();
    }
    std::io::stdout().write_all(b"!\n").unwrap();
}

$ cargo run
   Compiling magic-import v0.2.0
   Injecting std::print
   Injecting std::fs::File
   Injecting std::collections::BTreeMap
   Injecting std::io::Write
   Injecting std::unreachable
   Injecting std::result::Result::Ok
   Injecting std::str::FromStr
   Injecting std::path::PathBuf
    Finished dev [unoptimized + debuginfo] target(s) in 0.73s
     Running `target\debug\examples\example.exe`
123!

You can also specify the prefer_core feature flag to indicate that core:: should be used over std::, instead of the other way around:

$ cargo run
   Compiling magic-import v0.2.0
   Injecting std::collections::BTreeMap
   Injecting core::result::Result::Ok
   Injecting std::io::Write
   Injecting std::path::PathBuf
   Injecting std::fs::File
   Injecting std::str::FromStr
   Injecting std::print
   Injecting core::unreachable
    Finished dev [unoptimized + debuginfo] target(s) in 0.65s
     Running `target\debug\examples\example.exe`
123!

Note that it may still import from std:: if there is no suitable core:: import