is_compatible: Use semver::VersionReq to check compatibility

The hand-crafted compatibility check was incorrectly returning true with
debversion 0.1.0 and crateversion 0.1.1.  The patch version should be
honored if it's specified.

Since the semver crate is already being used, use semver::VersionReq to
check compatibility.

Signed-off-by: James McCoy <jamessan@debian.org>

src/db.rs

@@ -1,6 +1,6 @@
 use crate::errors::*;
 use postgres::{Client, NoTls};
-use semver::Version;
+use semver::{Version, VersionReq};
 use serde::{Deserialize, Serialize};
 use std::fs;
 use std::path::PathBuf;
@@ -16,22 +16,11 @@ pub struct CacheEntry {
 }
 
 // TODO: also use this for outdated check(?)
-fn is_compatible(debversion: &str, crateversion: &str) -> Result<bool, Error> {
+fn is_compatible(debversion: &str, crateversion: &VersionReq) -> Result<bool, Error> {
     let debversion = debversion.replace('~', "-");
-    let crateversion = crateversion.replace('~', "-");
-
     let debversion = Version::parse(&debversion)?;
-    let crateversion = Version::parse(&crateversion)?;
-
-    if debversion.major > 0 || crateversion.major > 0 {
-        return Ok(debversion.major == crateversion.major);
-    }
-
-    if debversion.minor > 0 || crateversion.minor > 0 {
-        return Ok(debversion.minor == crateversion.minor);
-    }
 
-    Ok(debversion.patch == crateversion.patch)
+    Ok(crateversion.matches(&debversion))
 }
 
 pub struct Connection {
@@ -142,6 +131,7 @@ impl Connection {
         let package = package.replace('_', "-");
         let rows = self.sock.query(query, &[&format!("rust-{package}")])?;
 
+        let version = VersionReq::parse(version)?;
         for row in &rows {
             let debversion: String = row.get(0);
 
@@ -152,7 +142,7 @@ impl Connection {
 
             // println!("{:?} ({:?}) => {:?}", debversion, version, is_compatible(debversion, version)?);
 
-            if is_compatible(debversion, version)? {
+            if is_compatible(debversion, &version)? {
                 return Ok(true);
             }
         }
@@ -164,9 +154,21 @@ impl Connection {
 #[cfg(test)]
 mod tests {
     use crate::db::is_compatible;
+    use semver::VersionReq;
 
     #[test]
     fn is_compatible_with_tilde() {
-        assert!(is_compatible("1.0.0~alpha.9", "1.0.0-alpha.9").unwrap());
+        assert!(is_compatible(
+            "1.0.0~alpha.9",
+            &VersionReq::parse("1.0.0-alpha.9").unwrap()
+        )
+        .unwrap());
+    }
+
+    #[test]
+    fn is_compatible_follows_semver() {
+        assert!(is_compatible("0.1.1", &VersionReq::parse("0.1.0").unwrap()).unwrap());
+        assert!(!is_compatible("0.1.0", &VersionReq::parse("0.1.1").unwrap()).unwrap());
+        assert!(is_compatible("1.1.0", &VersionReq::parse("1").unwrap()).unwrap());
     }
 }