Auto merge of #6910 - Eh2406:small-things, r=alexcrichton

bors · bors · commit 759b6161a328 · 2019-05-06T20:47:49.000Z
Small things This has two small changes that are worth saving from my most recent attempt to speedup #6258 (comment): 1. This removes the `ConflictCache::contains` added in #6776. Replacing it with a more general and easier to explain system based on the existing `ConflictCache::find_conflicting`. 2. This adds code to print the used part of the input for failing resolver tests. This is very helpful when 1. The proptest shrinking algorithm is interrupted, at least you have the smallest one found so far. 2. Hand minimizing, remove a dep and it will tell you all the packages that are no longer needed for the test to fail.
diff --git a/src/cargo/core/resolver/conflict_cache.rs b/src/cargo/core/resolver/conflict_cache.rs
@@ -18,20 +18,17 @@ enum ConflictStoreTrie {
 
 impl ConflictStoreTrie {
     /// Finds any known set of conflicts, if any,
-    /// which are activated in `cx` and contain `PackageId` specified.
+    /// where all elements return some from `is_active` and contain `PackageId` specified.
     /// If more then one are activated, then it will return
     /// one that will allow for the most jump-back.
-    fn find_conflicting(
+    fn find(
         &self,
-        cx: &Context,
+        is_active: &impl Fn(PackageId) -> Option<usize>,
         must_contain: Option<PackageId>,
     ) -> Option<(&ConflictMap, usize)> {
         match self {
             ConflictStoreTrie::Leaf(c) => {
                 if must_contain.is_none() {
-                    // `is_conflicting` checks that all the elements are active,
-                    // but we have checked each one by the recursion of this function.
-                    debug_assert!(cx.is_conflicting(None, c).is_some());
                     Some((c, 0))
                 } else {
                     // We did not find `must_contain`, so we need to keep looking.
@@ -45,9 +42,9 @@ impl ConflictStoreTrie {
                     .unwrap_or_else(|| m.range(..))
                 {
                     // If the key is active, then we need to check all of the corresponding subtrie.
-                    if let Some(age_this) = cx.is_active(pid) {
+                    if let Some(age_this) = is_active(pid) {
                         if let Some((o, age_o)) =
-                            store.find_conflicting(cx, must_contain.filter(|&f| f != pid))
+                            store.find(is_active, must_contain.filter(|&f| f != pid))
                         {
                             let age = if must_contain == Some(pid) {
                                 // all the results will include `must_contain`
@@ -102,28 +99,6 @@ impl ConflictStoreTrie {
             *self = ConflictStoreTrie::Leaf(con)
         }
     }
-
-    fn contains(&self, mut iter: impl Iterator<Item = PackageId>, con: &ConflictMap) -> bool {
-        match (self, iter.next()) {
-            (ConflictStoreTrie::Leaf(c), None) => {
-                if cfg!(debug_assertions) {
-                    let a: Vec<_> = con.keys().collect();
-                    let b: Vec<_> = c.keys().collect();
-                    assert_eq!(a, b);
-                }
-                true
-            }
-            (ConflictStoreTrie::Leaf(_), Some(_)) => false,
-            (ConflictStoreTrie::Node(_), None) => false,
-            (ConflictStoreTrie::Node(m), Some(n)) => {
-                if let Some(next) = m.get(&n) {
-                    next.contains(iter, con)
-                } else {
-                    false
-                }
-            }
-        }
-    }
 }
 
 pub(super) struct ConflictCache {
@@ -172,6 +147,17 @@ impl ConflictCache {
             dep_from_pid: HashMap::new(),
         }
     }
+    pub fn find(
+        &self,
+        dep: &Dependency,
+        is_active: &impl Fn(PackageId) -> Option<usize>,
+        must_contain: Option<PackageId>,
+    ) -> Option<&ConflictMap> {
+        self.con_from_dep
+            .get(dep)?
+            .find(is_active, must_contain)
+            .map(|(c, _)| c)
+    }
     /// Finds any known set of conflicts, if any,
     /// which are activated in `cx` and contain `PackageId` specified.
     /// If more then one are activated, then it will return
@@ -182,14 +168,11 @@ impl ConflictCache {
         dep: &Dependency,
         must_contain: Option<PackageId>,
     ) -> Option<&ConflictMap> {
-        let out = self
-            .con_from_dep
-            .get(dep)?
-            .find_conflicting(cx, must_contain)
-            .map(|(c, _)| c);
+        let out = self.find(dep, &|id| cx.is_active(id), must_contain);
         if cfg!(debug_assertions) {
-            if let Some(f) = must_contain {
-                if let Some(c) = &out {
+            if let Some(c) = &out {
+                assert!(cx.is_conflicting(None, c).is_some());
+                if let Some(f) = must_contain {
                     assert!(c.contains_key(&f));
                 }
             }
@@ -229,17 +212,6 @@ impl ConflictCache {
         }
     }
 
-    /// Check if a conflict was previously added of the form:
-    /// `dep` is known to be unresolvable if
-    /// all the `PackageId` entries are activated.
-    pub fn contains(&self, dep: &Dependency, con: &ConflictMap) -> bool {
-        if let Some(cst) = self.con_from_dep.get(dep) {
-            cst.contains(con.keys().cloned(), con)
-        } else {
-            false
-        }
-    }
-
     pub fn dependencies_conflicting_with(&self, pid: PackageId) -> Option<&HashSet<Dependency>> {
         self.dep_from_pid.get(&pid)
     }
diff --git a/src/cargo/core/resolver/mod.rs b/src/cargo/core/resolver/mod.rs
@@ -895,24 +895,61 @@ fn generalize_conflicting(
             // A dep is equivalent to one of the things it can resolve to.
             // Thus, if all the things it can resolve to have already ben determined
             // to be conflicting, then we can just say that we conflict with the parent.
-            if registry
+            if let Some(others) = registry
                 .query(critical_parents_dep)
                 .expect("an already used dep now error!?")
                 .iter()
                 .rev() // the last one to be tried is the least likely to be in the cache, so start with that.
-                .all(|other| {
-                    let mut con = conflicting_activations.clone();
-                    con.remove(&backtrack_critical_id);
-                    con.insert(
-                        other.summary.package_id(),
-                        backtrack_critical_reason.clone(),
-                    );
-                    past_conflicting_activations.contains(dep, &con)
+                .map(|other| {
+                    past_conflicting_activations
+                        .find(
+                            dep,
+                            &|id| {
+                                if id == other.summary.package_id() {
+                                    // we are imagining that we used other instead
+                                    Some(backtrack_critical_age)
+                                } else {
+                                    cx.is_active(id).filter(|&age|
+                                        // we only care about things that are older then critical_age
+                                        age < backtrack_critical_age)
+                                }
+                            },
+                            Some(other.summary.package_id()),
+                        )
+                        .map(|con| (other.summary.package_id(), con))
                 })
+                .collect::<Option<Vec<(PackageId, &ConflictMap)>>>()
             {
                 let mut con = conflicting_activations.clone();
-                con.remove(&backtrack_critical_id);
+                // It is always valid to combine previously inserted conflicts.
+                // A, B are both known bad states each that can never be activated.
+                // A + B is redundant but cant be activated, as if
+                // A + B is active then A is active and we know that is not ok.
+                for (_, other) in &others {
+                    con.extend(other.iter().map(|(&id, re)| (id, re.clone())));
+                }
+                // Now that we have this combined conflict, we can do a substitution:
+                // A dep is equivalent to one of the things it can resolve to.
+                // So we can remove all the things that it resolves to and replace with the parent.
+                for (other_id, _) in &others {
+                    con.remove(other_id);
+                }
                 con.insert(*critical_parent, backtrack_critical_reason);
+
+                if cfg!(debug_assertions) {
+                    // the entire point is to find an older conflict, so let's make sure we did
+                    let new_age = con
+                        .keys()
+                        .map(|&c| cx.is_active(c).expect("not currently active!?"))
+                        .max()
+                        .unwrap();
+                    assert!(
+                        new_age < backtrack_critical_age,
+                        "new_age {} < backtrack_critical_age {}",
+                        new_age,
+                        backtrack_critical_age
+                    );
+                }
                 past_conflicting_activations.insert(dep, &con);
                 return Some(con);
             }
diff --git a/tests/testsuite/support/resolver.rs b/tests/testsuite/support/resolver.rs
@@ -73,16 +73,20 @@ pub fn resolve_with_config_raw(
     registry: &[Summary],
     config: Option<&Config>,
 ) -> CargoResult<Resolve> {
-    struct MyRegistry<'a>(&'a [Summary]);
+    struct MyRegistry<'a> {
+        list: &'a [Summary],
+        used: HashSet<PackageId>,
+    };
     impl<'a> Registry for MyRegistry<'a> {
         fn query(
             &mut self,
             dep: &Dependency,
             f: &mut dyn FnMut(Summary),
             fuzzy: bool,
         ) -> CargoResult<()> {
-            for summary in self.0.iter() {
+            for summary in self.list.iter() {
                 if fuzzy || dep.matches(summary) {
+                    self.used.insert(summary.package_id());
                     f(summary.clone());
                 }
             }
@@ -97,7 +101,28 @@ pub fn resolve_with_config_raw(
             false
         }
     }
-    let mut registry = MyRegistry(registry);
+    impl<'a> Drop for MyRegistry<'a> {
+        fn drop(&mut self) {
+            if std::thread::panicking() && self.list.len() != self.used.len() {
+                // 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.
+                println!(
+                    "{:?}",
+                    PrettyPrintRegistry(
+                        self.list
+                            .iter()
+                            .filter(|s| { self.used.contains(&s.package_id()) })
+                            .cloned()
+                            .collect()
+                    )
+                );
+            }
+        }
+    }
+    let mut registry = MyRegistry {
+        list: registry,
+        used: HashSet::new(),
+    };
     let summary = Summary::new(
         pkg,
         deps,
@@ -348,8 +373,6 @@ fn meta_test_deep_pretty_print_registry() {
                 pkg!(("baz", "1.0.1")),
                 pkg!(("cat", "1.0.2") => [dep_req_kind("other", "2", Kind::Build, false)]),
                 pkg!(("cat", "1.0.3") => [dep_req_kind("other", "2", Kind::Development, false)]),
-                pkg!(("cat", "1.0.4") => [dep_req_kind("other", "2", Kind::Build, false)]),
-                pkg!(("cat", "1.0.5") => [dep_req_kind("other", "2", Kind::Development, false)]),
                 pkg!(("dep_req", "1.0.0")),
                 pkg!(("dep_req", "2.0.0")),
             ])
@@ -363,8 +386,6 @@ fn meta_test_deep_pretty_print_registry() {
          pkg!((\"baz\", \"1.0.1\")),\
          pkg!((\"cat\", \"1.0.2\") => [dep_req_kind(\"other\", \"^2\", Kind::Build, false),]),\
          pkg!((\"cat\", \"1.0.3\") => [dep_req_kind(\"other\", \"^2\", Kind::Development, false),]),\
-         pkg!((\"cat\", \"1.0.4\") => [dep_req_kind(\"other\", \"^2\", Kind::Build, false),]),\
-         pkg!((\"cat\", \"1.0.5\") => [dep_req_kind(\"other\", \"^2\", Kind::Development, false),]),\
          pkg!((\"dep_req\", \"1.0.0\")),\
          pkg!((\"dep_req\", \"2.0.0\")),]"
     )
