If there's a version in the lock file only use that exact version

src/cargo/sources/registry/index.rs

@@ -437,11 +437,13 @@ impl<'cfg> RegistryIndex<'cfg> {
     /// checking the integrity of a downloaded package matching the checksum in
     /// the index file, aka [`IndexSummary`].
     pub fn hash(&mut self, pkg: PackageId, load: &mut dyn RegistryData) -> Poll<CargoResult<&str>> {
-        let req = OptVersionReq::exact(pkg.version());
+        let mut req = OptVersionReq::exact(pkg.version());
+        // Since crates.io allows crate versions to differ only by build metadata,
+        // a query using OptVersionReq::exact + next() can return nondeterministic results.
+        // So we `lock_to` the exact version were interested in
+        req.lock_to(pkg.version());
         let summary = self.summaries(pkg.name(), &req, load)?;
-        let summary = ready!(summary)
-            .filter(|s| s.package_id().version() == pkg.version())
-            .next();
+        let summary = ready!(summary).next();
         Poll::Ready(Ok(summary
             .ok_or_else(|| internal(format!("no hash listed for {}", pkg)))?
             .as_summary()
@@ -698,10 +700,13 @@ impl<'cfg> RegistryIndex<'cfg> {
         pkg: PackageId,
         load: &mut dyn RegistryData,
     ) -> Poll<CargoResult<bool>> {
-        let req = OptVersionReq::exact(pkg.version());
-        let found = ready!(self.summaries(pkg.name(), &req, load))?
-            .filter(|s| s.package_id().version() == pkg.version())
-            .any(|s| s.is_yanked());
+        let mut req = OptVersionReq::exact(pkg.version());
+
+        // Since crates.io allows crate versions to differ only by build metadata,
+        // a query using OptVersionReq::exact + next() can return nondeterministic results.
+        // So we `lock_to` the exact version were interested in
+        req.lock_to(pkg.version());
+        let found = ready!(self.summaries(pkg.name(), &req, load))?.any(|s| s.is_yanked());
         Poll::Ready(Ok(found))
     }
 }

src/cargo/util/semver_ext.rs

@@ -84,10 +84,14 @@ impl OptVersionReq {
             OptVersionReq::Any => true,
             OptVersionReq::Req(req) => req.matches(version),
             OptVersionReq::Locked(v, _) => {
-                v.major == version.major
-                    && v.minor == version.minor
-                    && v.patch == version.patch
-                    && v.pre == version.pre
+                // Generally, cargo is of the opinion that semver metadata should be ignored.
+                // If your registry has two versions that only differing metadata you get the bugs you deserve.
+                // We also believe that lock files should ensure reproducibility
+                // and protect against mutations from the registry.
+                // In this circumstance these two goals are in conflict, and we pick reproducibility.
+                // If the lock file tells us that there is a version called `1.0.0+bar` then
+                // we should not silently use `1.0.0+foo` even though they have the same version.
+                v == version
             }
         }
     }
@@ -311,40 +315,3 @@ fn is_req(value: &str) -> bool {
     };
     "<>=^~".contains(first) || value.contains('*') || value.contains(',')
 }
-
-#[cfg(test)]
-mod tests {
-    use super::*;
-
-    #[test]
-    fn locked_has_the_same_with_exact() {
-        fn test_versions(target_ver: &str, vers: &[&str]) {
-            let ver = Version::parse(target_ver).unwrap();
-            let exact = OptVersionReq::exact(&ver);
-            let mut locked = exact.clone();
-            locked.lock_to(&ver);
-            for v in vers {
-                let v = Version::parse(v).unwrap();
-                assert_eq!(exact.matches(&v), locked.matches(&v));
-            }
-        }
-
-        test_versions(
-            "1.0.0",
-            &["1.0.0", "1.0.1", "0.9.9", "0.10.0", "0.1.0", "1.0.0-pre"],
-        );
-        test_versions("0.9.0", &["0.9.0", "0.9.1", "1.9.0", "0.0.9", "0.9.0-pre"]);
-        test_versions("0.0.2", &["0.0.2", "0.0.1", "0.0.3", "0.0.2-pre"]);
-        test_versions(
-            "0.1.0-beta2.a",
-            &[
-                "0.1.0-beta2.a",
-                "0.9.1",
-                "0.1.0",
-                "0.1.1-beta2.a",
-                "0.1.0-beta2",
-            ],
-        );
-        test_versions("0.1.0+meta", &["0.1.0", "0.1.0+meta", "0.1.0+any"]);
-    }
-}