disable back jumping on pub dep error

Author: Eh2406

src/cargo/core/resolver/conflict_cache.rs

@@ -173,6 +173,11 @@ impl ConflictCache {
     /// `dep` is known to be unresolvable if
     /// all the `PackageId` entries are activated.
     pub fn insert(&mut self, dep: &Dependency, con: &BTreeMap<PackageId, ConflictReason>) {
+        if con.values().any(|c| *c == ConflictReason::PublicDependency) {
+            // TODO: needs more info for back jumping
+            // for now refuse to cache it.
+            return;
+        }
         self.con_from_dep
             .entry(dep.clone())
             .or_insert_with(|| ConflictStoreTrie::Node(BTreeMap::new()))

src/cargo/core/resolver/mod.rs

@@ -782,7 +782,7 @@ impl RemainingCandidates {
                     // TODO: dont look at the same thing more then once
                     if let Some(o) = cx.public_dependency.get(&p).and_then(|x| x.get(&t.name())) {
                         if o.0 != t {
-                            // TODO: conflicting_prev_active
+                            conflicting_prev_active.insert(p, ConflictReason::PublicDependency);
                             continue 'main;
                         }
                     }
@@ -868,6 +868,9 @@ fn find_candidate(
         // make any progress. As a result if we hit this condition we can
         // completely skip this backtrack frame and move on to the next.
         if !backtracked
+            && !conflicting_activations
+                .values()
+                .any(|c| *c == ConflictReason::PublicDependency)
             && frame
                 .context
                 .is_conflicting(Some(parent.package_id()), conflicting_activations)

src/cargo/core/resolver/types.rs

@@ -402,6 +402,11 @@ pub enum ConflictReason {
     /// candidate. For example we tried to activate feature `foo` but the
     /// candidate we're activating didn't actually have the feature `foo`.
     MissingFeatures(String),
+
+    // TODO: needs more info for errors maneges
+    // TODO: needs more info for back jumping
+    /// pub dep errore
+    PublicDependency,
 }
 
 impl ConflictReason {

tests/testsuite/resolve.rs

@@ -328,6 +328,43 @@ fn public_dependency_filling_in_and_update() {
     );
 }
 
+#[test]
+fn public_dependency_skiping() {
+    // When backtracking due to a failed dependency, if Cargo is
+    // trying to be clever and skip irrelevant dependencies, care must
+    // the effects of pub dep must be accounted for.
+    let input = vec![
+        pkg!(("a", "0.2.0")),
+        pkg!(("a", "2.0.0")),
+        pkg!(("b", "0.0.0") => [dep("bad")]),
+        pkg!(("b", "0.2.1") => [dep_req_kind("a", "0.2.0", Kind::Normal, true)]),
+        pkg!("c" => [dep("a"),dep("b")]),
+    ];
+    let reg = registry(input.clone());
+
+    resolve(&pkg_id("root"), vec![dep("c")], &reg).unwrap();
+}
+
+#[test]
+fn public_dependency_skiping_in_backtracking() {
+    // When backtracking due to a failed dependency, if Cargo is
+    // trying to be clever and skip irrelevant dependencies, care must
+    // the effects of pub dep must be accounted for.
+    let input = vec![
+        pkg!(("A", "0.0.0") => [dep("bad")]),
+        pkg!(("A", "0.0.1") => [dep("bad")]),
+        pkg!(("A", "0.0.2") => [dep("bad")]),
+        pkg!(("A", "0.0.3") => [dep("bad")]),
+        pkg!(("A", "0.0.4")),
+        pkg!(("A", "0.0.5")),
+        pkg!("B" => [dep_req_kind("A", ">= 0.0.3", Kind::Normal, true)]),
+        pkg!("C" => [dep_req("A", "<= 0.0.4"), dep("B")]),
+    ];
+    let reg = registry(input.clone());
+
+    resolve(&pkg_id("root"), vec![dep("C")], &reg).unwrap();
+}
+
 #[test]
 #[should_panic(expected = "assertion failed: !name.is_empty()")]
 fn test_dependency_with_empty_name() {