If the only path is a loop then counted as the shortest path.

src/cargo/util/graph.rs

@@ -165,8 +165,12 @@ impl<'s, N: Eq + Ord + Clone + 's, E: Default + Clone + 's> Graph<N, E> {
  ));
  }
  let last = result.last().unwrap().0;
- // fixme: this may sometimes be wrong when there are cycles.
- if !fn_edge(&self, last).next().is_none() {
+ let set: Vec<_> = result.iter().map(|(k, _)| k).collect();
+ if !fn_edge(&self, last)
+ .filter(|(e, _)| !set.contains(&e))
+ .next()
+ .is_none()
+ {
  self.print_for_test();
  unreachable!("The last element in the path should not have outgoing edges");
  }
@@ -188,6 +192,14 @@ fn path_to_case() {
  );
 }
 
+#[test]
+fn path_to_self() {
+ // Extracted from #12941
+ let mut new: Graph<i32, ()> = Graph::new();
+ new.link(0, 0);
+ assert_eq!(new.path_to_bottom(&0), vec![(&0, None)]);
+}
+
 impl<N: Eq + Ord + Clone, E: Default + Clone> Default for Graph<N, E> {
  fn default() -> Graph<N, E> {
  Graph::new()

tests/testsuite/test.rs

@@ -3555,6 +3555,34 @@ fn cyclic_dev() {
  p.cargo("test --workspace").run();
 }
 
+#[cargo_test]
+fn cyclical_dep_with_missing_feature() {
+ // Checks for error handling when a cyclical dev-dependency specify a
+ // feature that doesn't exist.
+ let p = project()
+ .file(
+ "Cargo.toml",
+ r#"
+ [package]
+ name = "foo"
+ version = "0.1.0"
+
+ [dev-dependencies]
+ foo = { path = ".", features = ["missing"] }
+ "#,
+ )
+ .file("src/lib.rs", "")
+ .build();
+ p.cargo("check")
+ .with_status(101)
+ .with_stderr(
+ "thread 'main' panicked at src/cargo/util/graph.rs:149:20:
+the only path was a cycle, no dependency graph has this shape
+note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace",
+ )
+ .run();
+}
+
 #[cargo_test]
 fn publish_a_crate_without_tests() {
  Package::new("testless", "0.1.0")