add a test for shortest path

Author: Eh2406

crates/resolver-tests/src/lib.rs

@@ -164,7 +164,7 @@ pub fn resolve_with_config_raw(
                 // we found a case that causes a panic and did not use all of the input.
                 // lets print the part of the input that was used for minimization.
                 eprintln!(
-                    "{:?}",
+                    "Part used befor drop: {:?}",
                     PrettyPrintRegistry(
                         self.list
                             .iter()

crates/resolver-tests/tests/resolve.rs

@@ -1562,3 +1562,37 @@ package `A v0.0.0 (registry `https://example.com/`)`
     ... which satisfies dependency `C = \"*\"` of package `A v0.0.0 (registry `https://example.com/`)`\
 ", error.to_string());
 }
+
+#[test]
+fn shortest_path_in_error_message() {
+    let input = vec![
+        pkg!(("F", "0.1.2")),
+        pkg!(("F", "0.1.1") => [dep("bad"),]),
+        pkg!(("F", "0.1.0") => [dep("bad"),]),
+        pkg!("E" => [dep_req("F", "^0.1.2"),]),
+        pkg!("D" => [dep_req("F", "^0.1.2"),]),
+        pkg!("C" => [dep("D"),]),
+        pkg!("A" => [dep("C"),dep("E"),dep_req("F", "<=0.1.1"),]),
+    ];
+    let error = resolve(vec![dep("A")], &registry(input)).unwrap_err();
+    println!("{}", error);
+    assert_eq!(
+        "\
+failed to select a version for `F`.
+    ... required by package `A v1.0.0 (registry `https://example.com/`)`
+    ... which satisfies dependency `A = \"*\"` of package `root v1.0.0 (registry `https://example.com/`)`
+versions that meet the requirements `<=0.1.1` are: 0.1.1, 0.1.0
+
+all possible versions conflict with previously selected packages.
+
+  previously selected package `F v0.1.2 (registry `https://example.com/`)`
+    ... which satisfies dependency `F = \"^0.1.2\"` of package `D v1.0.0 (registry `https://example.com/`)`
+    ... which satisfies dependency `D = \"*\"` of package `C v1.0.0 (registry `https://example.com/`)`
+    ... which satisfies dependency `C = \"*\"` of package `A v1.0.0 (registry `https://example.com/`)`
+    ... which satisfies dependency `A = \"*\"` of package `root v1.0.0 (registry `https://example.com/`)`
+
+failed to select a version for `F` which could resolve this conflict\
+    ",
+        error.to_string()
+    );
+}

src/cargo/core/resolver/dep_cache.rs

@@ -131,9 +131,8 @@ impl<'a> RegistryQueryer<'a> {
                 .iter()
                 .filter(|(spec, _)| spec.matches(summary.package_id()));
 
-            let (spec, dep) = match potential_matches.next() {
-                None => continue,
-                Some(replacement) => replacement,
+            let Some((spec, dep)) = potential_matches.next() else {
+                continue;
             };
             debug!(
                 "found an override for {} {}",