test: simplify rust_version::sync

Cargo.toml

@@ -39,7 +39,5 @@ pipe-trait = "0.4.0"
 split-first-char = "0.0.0"
 
 [dev-dependencies]
-cargo_metadata = "0.18.1"
-cargo_toml = "0.20.5"
 pretty_assertions = "1.4.1"
 semver = "1.0.23"

tests/rust_version.rs

@@ -1,19 +1,13 @@
 #![cfg(feature = "std")]
-use cargo_metadata::MetadataCommand;
-use cargo_toml::Manifest;
 use pipe_trait::Pipe;
 use pretty_assertions::assert_eq;
 use semver::Version;
-use std::fs;
+use std::{fs, path::Path};
 
 #[test]
 fn sync() {
-    let ws_root = MetadataCommand::new()
-        .exec()
-        .expect("the command `cargo metadata` should execute successfully")
-        .workspace_root;
-    dbg!(&ws_root);
-    let rust_toolchain = ws_root
+    let rust_toolchain = env!("CARGO_MANIFEST_DIR")
+        .pipe(Path::new)
         .join("rust-toolchain")
         .pipe(fs::read_to_string)
         .expect("the rust-toolchain file should be readable")
@@ -22,18 +16,7 @@ fn sync() {
         .expect("the content rust-toolchain should be valid semver");
     dbg!(&rust_toolchain);
     let Version { major, minor, .. } = &rust_toolchain;
-    let rust_version = ws_root
-        .join("Cargo.toml")
-        .pipe(Manifest::from_path)
-        .expect("Cargo.toml should be readable")
-        .package
-        .expect("package should be defined")
-        .rust_version
-        .expect("rust_version should be defined");
-    let rust_version = rust_version
-        .get()
-        .expect("rust-version should be valid")
-        .as_str();
+    let rust_version = env!("CARGO_PKG_RUST_VERSION");
     dbg!(rust_version);
     assert_eq!(rust_version, format!("{major}.{minor}"));
 }