cfg-version 1.0.0

Conditional compilation based on dependency versions.
Documentation

cfg-version

Conditional compilation based on dependency versions.

Usage

[dependencies]
cfg-version = "0.1"

use cfg_version::cfg_version;

#[cfg_version(indexmap = "^2.8")]
fn needs_indexmap_2_8() { }

Version syntax

Uses Cargo's semver syntax:

Syntax Example Meaning
^ (default) "^2.8" or "2.8" >= 2.8.0, < 3.0.0
~ "~2.8" >= 2.8.0, < 2.9.0
>= ">=2.8" >= 2.8.0
> ">2.8" > 2.8.0
< "<3" < 3.0.0
<= "<=2.8" <= 2.8.0
= "=2.8.0" exactly 2.8.0
* "*" any version
combined ">=2.8, <2.12" >= 2.8.0 and < 2.12.0

How it works

At macro expansion time, cfg-version:

  1. Reads CARGO_PKG_NAME to identify the current crate.
  2. Finds Cargo.lock by walking up from CARGO_MANIFEST_DIR.
  3. Parses the lock file to find the current crate's direct dependencies and their resolved versions.
  4. Matches the resolved version against the user-specified requirement.
  5. Keeps or removes the annotated item accordingly.

When a dependency appears multiple times in Cargo.lock (e.g., syn 1.x and 2.x), only the version directly depended on by the current crate is considered.

License

MIT