Fix --mutually-exclusive-features containing optional deps.

Author: xStrom

src/features.rs

@@ -160,7 +160,16 @@ impl Feature {
         ) -> bool {
             if let Some(v) = map.get(cur) {
                 for cur in v {
-                    if cur != root && (group.matches(cur) || rec(group, map, cur, root)) {
+                    let fname = if let Some(slash_idx) = cur.find('/') {
+                        // The fname may still have a '?' suffix, which is fine.
+                        // Because in that case it doesn't activate that dependency, so it can be ignored.
+                        let (fname, _) = cur.split_at(slash_idx);
+                        fname
+                    } else {
+                        // Could be 'dep:something', which is fine because it's not a feature.
+                        cur
+                    };
+                    if fname != root && (group.matches(fname) || rec(group, map, fname, root)) {
                         return true;
                     }
                 }
@@ -396,6 +405,25 @@ mod tests {
             vec!["b", "async-std"]
         ]);
 
+        let map = map![
+            ("tokio", v![]),
+            ("async-std", v![]),
+            ("a", v!["tokio/full"]),
+            ("b", v!["async-std?/alloc"])
+        ];
+        let list = v!["a", "b", "tokio", "async-std"];
+        let mutually_exclusive_features = [Feature::group(["tokio", "async-std"])];
+        let filtered = feature_powerset(&list, None, &[], &mutually_exclusive_features, &map);
+        assert_eq!(filtered, vec![
+            vec!["a"],
+            vec!["b"],
+            vec!["a", "b"],
+            vec!["tokio"],
+            vec!["b", "tokio"],
+            vec!["async-std"],
+            vec!["b", "async-std"]
+        ]);
+
         let map = map![("a", v![]), ("b", v!["a"]), ("c", v![]), ("d", v!["b"])];
         let list = v!["a", "b", "c", "d"];
         let mutually_exclusive_features = [Feature::group(["a", "c"])];