Add new trait VersionReqExt and impl it for VersionReq

Signed-off-by: Jiahao XU <Jiahao_XU@outlook.com>

src/helpers.rs

@@ -51,6 +51,9 @@ pub use flock::FileLock;
 mod signal;
 pub use signal::cancel_on_user_sig_term;
 
+mod version;
+pub use version::VersionReqExt;
+
 pub fn cargo_home() -> Result<&'static Path, io::Error> {
     static CARGO_HOME: OnceCell<PathBuf> = OnceCell::new();
 

src/helpers/version.rs

@@ -0,0 +1,78 @@
+use compact_str::format_compact;
+use semver::{Prerelease, Version, VersionReq};
+
+/// Extension trait for [`VersionReq`].
+pub trait VersionReqExt {
+    /// Return `true` if `self.matches(version)` returns `true`
+    /// and the `version` is the latest one acceptable by `self`.
+    fn is_latest_compatible(&self, version: &Version) -> bool;
+}
+
+impl VersionReqExt for VersionReq {
+    fn is_latest_compatible(&self, version: &Version) -> bool {
+        if !self.matches(version) {
+            return false;
+        }
+
+        // Test if bumping patch will be accepted
+        let bumped_version = Version::new(version.major, version.minor, version.patch + 1);
+
+        if self.matches(&bumped_version) {
+            return false;
+        }
+
+        // Test if bumping prerelease will be accepted if version has one.
+        let pre = &version.pre;
+        if !pre.is_empty() {
+            // Bump pre by appending random number to the end.
+            let bumped_pre = format_compact!("{}.1", pre.as_str());
+
+            let bumped_version = Version {
+                major: version.major,
+                minor: version.minor,
+                patch: version.patch,
+                pre: Prerelease::new(&bumped_pre).unwrap(),
+                build: Default::default(),
+            };
+
+            if self.matches(&bumped_version) {
+                return false;
+            }
+        }
+
+        true
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test() {
+        // Test star
+        assert!(!VersionReq::STAR.is_latest_compatible(&Version::parse("0.0.1").unwrap()));
+        assert!(!VersionReq::STAR.is_latest_compatible(&Version::parse("0.1.1").unwrap()));
+        assert!(!VersionReq::STAR.is_latest_compatible(&Version::parse("0.1.1-alpha").unwrap()));
+
+        // Test ^x.y.z
+        assert!(!VersionReq::parse("^0.1")
+            .unwrap()
+            .is_latest_compatible(&Version::parse("0.1.99").unwrap()));
+
+        // Test =x.y.z
+        assert!(VersionReq::parse("=0.1.0")
+            .unwrap()
+            .is_latest_compatible(&Version::parse("0.1.0").unwrap()));
+
+        // Test =x.y.z-alpha
+        assert!(VersionReq::parse("=0.1.0-alpha")
+            .unwrap()
+            .is_latest_compatible(&Version::parse("0.1.0-alpha").unwrap()));
+
+        // Test >=x.y.z-alpha
+        assert!(!VersionReq::parse(">=0.1.0-alpha")
+            .unwrap()
+            .is_latest_compatible(&Version::parse("0.1.0-alpha").unwrap()));
+    }
+}