fix(driver): start the commit's certificate round

code/crates/core-driver/src/driver.rs

@@ -241,7 +241,7 @@ where
         }
     }
 
-    /// Get a commit certificate for the given round and value id.
+    /// Get a commit certificate for the given round and value id, if any.
     pub fn commit_certificate(
         &self,
         round: Round,
@@ -252,6 +252,16 @@ where
             .find(|c| &c.value_id == value_id && c.round == round && c.height == self.height())
     }
 
+    /// Get a commit certificate for the given round, if any.
+    pub fn commit_certificate_for_round(
+        &self,
+        round: Round,
+    ) -> Option<&CommitCertificate<Ctx>> {
+        self.commit_certificates
+            .iter()
+            .find(|c| c.round == round && c.height == self.height())
+    }
+
     /// Return the commit certificates, if any.
     pub fn commit_certificates(&self) -> &[CommitCertificate<Ctx>] {
         self.commit_certificates.as_ref()

code/crates/core-driver/src/mux.rs

@@ -214,7 +214,9 @@ where
         // Store the certificate
         self.commit_certificates.push(certificate);
 
-        if let Some((signed_proposal, validity)) =
+        if certificate_round > self.round() {
+            return Some(RoundInput::SkipRound(certificate_round));
+        } else if let Some((signed_proposal, validity)) =
             self.proposal_and_validity_for_round_and_value(certificate_round, certificate_value_id)
         {
             if validity.is_valid() {
@@ -399,6 +401,10 @@ where
         for threshold in find_non_value_threshold(&self.vote_keeper, round) {
             result.push(self.multiplex_vote_threshold(threshold, round))
         }
+        // This is equivalent of having a VKOutput::PrecommitAny
+        if self.commit_certificate_for_round(round).is_some() {
+            result.push(self.multiplex_vote_threshold(VKOutput::PrecommitAny, round));
+        }
         result
     }
 }

code/crates/core-driver/tests/it/extra.rs

@@ -2977,7 +2977,7 @@ fn polka_nil_and_prevote_step_precommit_nil() {
                 prevote_nil_output(Round::new(0), &my_addr),
                 precommit_nil_output(Round::new(0), &my_addr),
                 start_precommit_timer_output(Round::new(0)),
-                start_precommit_timer_output(Round::new(0)),
+                start_precommit_timer_output(Round::new(0)), // :'(
             ],
             expected_round: Round::new(0),
             new_state: precommit_state(Round::new(0)),
@@ -3646,6 +3646,264 @@ fn sync_decision_certificate_then_proposal() {
     run_steps(&mut driver, steps);
 }
 
+#[test]
+fn round_1_decision_during_round_0_with_votes() {
+    let value = Value::new(9999);
+
+    let [(v1, _sk1), (v2, _sk2), (v3, sk3)] = make_validators([2, 3, 2]);
+    let (_my_sk, my_addr) = (sk3.clone(), v3.address);
+
+    let height = Height::new(1);
+    let ctx = TestContext::new();
+    let vs = ValidatorSet::new(vec![v1.clone(), v2.clone(), v3.clone()]);
+
+    let proposal = Proposal::new(
+        Height::new(1),
+        Round::new(1),
+        value.clone(),
+        Round::Nil,
+        v1.address,
+    );
+
+    let mut driver = Driver::new(ctx, height, vs, my_addr, Default::default());
+
+    let steps = vec![
+        TestStep {
+            desc: "Start round 0, we are not the proposer",
+            input: new_round_input(Round::new(0), v1.address),
+            expected_outputs: vec![start_propose_timer_output(Round::new(0))],
+            expected_round: Round::new(0),
+            new_state: propose_state(Round::new(0)),
+        },
+        TestStep {
+            desc: "v1 precommits a proposal in round 1",
+            input: precommit_input(Round::new(1), value.clone(), &v1.address),
+            expected_outputs: vec![],
+            expected_round: Round::new(0),
+            new_state: propose_state(Round::new(0)),
+        },
+        TestStep {
+            desc: "Receive proposal from round 1",
+            input: proposal_input_from_proposal(proposal.clone(), Validity::Valid),
+            expected_outputs: vec![],
+            expected_round: Round::new(0),
+            new_state: propose_state(Round::new(0)),
+        },
+        TestStep {
+            desc: "v2 precommits the same round 1 proposal, move to round 1",
+            input: precommit_input(Round::new(1), value.clone(), &v2.address),
+            expected_outputs: vec![new_round_output(Round::new(1))],
+            expected_round: Round::new(1),
+            new_state: new_round(Round::new(1)),
+        },
+        TestStep {
+            desc: "Start round 1 and decide immediately",
+            input: new_round_input(Round::new(1), v2.address),
+            expected_outputs: vec![
+                start_propose_timer_output(Round::new(1)),
+                decide_output(Round::new(1), proposal),
+            ],
+            expected_round: Round::new(1),
+            new_state: decided_state(Round::new(1), Round::new(1), value),
+        },
+    ];
+
+    run_steps(&mut driver, steps);
+}
+
+#[test]
+fn round_1_decision_during_round_0_via_certificate() {
+    let value = Value::new(9999);
+
+    let [(v1, _sk1), (v2, _sk2), (v3, sk3)] = make_validators([2, 3, 2]);
+    let (_my_sk, my_addr) = (sk3.clone(), v3.address);
+
+    let height = Height::new(1);
+    let ctx = TestContext::new();
+    let vs = ValidatorSet::new(vec![v1.clone(), v2.clone(), v3.clone()]);
+
+    let proposal = Proposal::new(
+        Height::new(1),
+        Round::new(1),
+        value.clone(),
+        Round::Nil,
+        v1.address,
+    );
+
+    let mut driver = Driver::new(ctx, height, vs, my_addr, Default::default());
+
+    let steps = vec![
+        TestStep {
+            desc: "Start round 0, we are not the proposer",
+            input: new_round_input(Round::new(0), v1.address),
+            expected_outputs: vec![start_propose_timer_output(Round::new(0))],
+            expected_round: Round::new(0),
+            new_state: propose_state(Round::new(0)),
+        },
+        TestStep {
+            desc: "Receive proposal from round 1",
+            input: proposal_input_from_proposal(proposal.clone(), Validity::Valid),
+            expected_outputs: vec![],
+            expected_round: Round::new(0),
+            new_state: propose_state(Round::new(0)),
+        },
+        TestStep {
+            desc: "we get a commit certificate for v at round 1, move to round 1",
+            input: commit_certificate_input_at(
+                Round::new(1),
+                value.clone(),
+                &[v1.address, v2.address],
+            ),
+            expected_outputs: vec![new_round_output(Round::new(1))],
+            expected_round: Round::new(1),
+            new_state: new_round(Round::new(1)),
+        },
+        TestStep {
+            desc: "Start round 1 and decide immediately",
+            input: new_round_input(Round::new(1), v2.address),
+            expected_outputs: vec![
+                start_propose_timer_output(Round::new(1)),
+                decide_output(Round::new(1), proposal),
+            ],
+            expected_round: Round::new(1),
+            new_state: decided_state(Round::new(1), Round::new(1), value),
+        },
+    ];
+
+    run_steps(&mut driver, steps);
+}
+
+#[test]
+fn round_1_invalid_decision_during_round_0_with_votes() {
+    let value = Value::new(9999);
+
+    let [(v1, _sk1), (v2, _sk2), (v3, sk3)] = make_validators([2, 3, 2]);
+    let (_my_sk, my_addr) = (sk3.clone(), v3.address);
+
+    let height = Height::new(1);
+    let ctx = TestContext::new();
+    let vs = ValidatorSet::new(vec![v1.clone(), v2.clone(), v3.clone()]);
+
+    let proposal = Proposal::new(
+        Height::new(1),
+        Round::new(1),
+        value.clone(),
+        Round::Nil,
+        v1.address,
+    );
+
+    let mut driver = Driver::new(ctx, height, vs, my_addr, Default::default());
+
+    let steps = vec![
+        TestStep {
+            desc: "Start round 0, we are not the proposer",
+            input: new_round_input(Round::new(0), v1.address),
+            expected_outputs: vec![start_propose_timer_output(Round::new(0))],
+            expected_round: Round::new(0),
+            new_state: propose_state(Round::new(0)),
+        },
+        TestStep {
+            desc: "v1 precommits a proposal in round 1",
+            input: precommit_input(Round::new(1), value.clone(), &v1.address),
+            expected_outputs: vec![],
+            expected_round: Round::new(0),
+            new_state: propose_state(Round::new(0)),
+        },
+        TestStep {
+            desc: "Receive proposal from round 1, which is invalid",
+            input: proposal_input_from_proposal(proposal.clone(), Validity::Invalid),
+            expected_outputs: vec![],
+            expected_round: Round::new(0),
+            new_state: propose_state(Round::new(0)),
+        },
+        TestStep {
+            desc: "v2 precommits the same round 1 proposal, move to round 1",
+            input: precommit_input(Round::new(1), value.clone(), &v2.address),
+            expected_outputs: vec![new_round_output(Round::new(1))],
+            expected_round: Round::new(1),
+            new_state: new_round(Round::new(1)),
+        },
+        TestStep {
+            desc: "Start round 1 but does not decide invalid proposal",
+            input: new_round_input(Round::new(1), v2.address),
+            expected_outputs: vec![
+                start_propose_timer_output(Round::new(1)),
+                prevote_nil_output(Round::new(1), &my_addr),
+                start_precommit_timer_output(Round::new(1)),
+                start_precommit_timer_output(Round::new(1)), // :'(
+            ],
+            expected_round: Round::new(1),
+            new_state: prevote_state(Round::new(1)),
+        },
+    ];
+
+    run_steps(&mut driver, steps);
+}
+
+#[test]
+fn round_1_invalid_decision_during_round_0_via_certificate() {
+    let value = Value::new(9999);
+
+    let [(v1, _sk1), (v2, _sk2), (v3, sk3)] = make_validators([2, 3, 2]);
+    let (_my_sk, my_addr) = (sk3.clone(), v3.address);
+
+    let height = Height::new(1);
+    let ctx = TestContext::new();
+    let vs = ValidatorSet::new(vec![v1.clone(), v2.clone(), v3.clone()]);
+
+    let proposal = Proposal::new(
+        Height::new(1),
+        Round::new(1),
+        value.clone(),
+        Round::Nil,
+        v1.address,
+    );
+
+    let mut driver = Driver::new(ctx, height, vs, my_addr, Default::default());
+
+    let steps = vec![
+        TestStep {
+            desc: "Start round 0, we are not the proposer",
+            input: new_round_input(Round::new(0), v1.address),
+            expected_outputs: vec![start_propose_timer_output(Round::new(0))],
+            expected_round: Round::new(0),
+            new_state: propose_state(Round::new(0)),
+        },
+        TestStep {
+            desc: "Receive proposal from round 1, which is invalid",
+            input: proposal_input_from_proposal(proposal.clone(), Validity::Invalid),
+            expected_outputs: vec![],
+            expected_round: Round::new(0),
+            new_state: propose_state(Round::new(0)),
+        },
+        TestStep {
+            desc: "we get a commit certificate for v at round 1, move to round 1",
+            input: commit_certificate_input_at(
+                Round::new(1),
+                value.clone(),
+                &[v1.address, v2.address],
+            ),
+            expected_outputs: vec![new_round_output(Round::new(1))],
+            expected_round: Round::new(1),
+            new_state: new_round(Round::new(1)),
+        },
+        TestStep {
+            desc: "Start round 1 but does not decide invalid proposal",
+            input: new_round_input(Round::new(1), v2.address),
+            expected_outputs: vec![
+                start_propose_timer_output(Round::new(1)),
+                prevote_nil_output(Round::new(1), &my_addr),
+                start_precommit_timer_output(Round::new(1)),
+                start_precommit_timer_output(Round::new(1)), // :'(
+            ],
+            expected_round: Round::new(1),
+            new_state: prevote_state(Round::new(1)),
+        },
+    ];
+
+    run_steps(&mut driver, steps);
+}
+
 fn run_steps(driver: &mut Driver<TestContext>, steps: Vec<TestStep>) {
     let mut last_step = Step::Unstarted;
     for step in steps {

code/crates/core-votekeeper/tests/vote_keeper.rs

@@ -1,6 +1,7 @@
-use malachitebft_core_types::{NilOrVal, Round, SignedVote};
+use malachitebft_core_types::{NilOrVal, Round, SignedVote, VoteType};
 
 use informalsystems_malachitebft_core_votekeeper::keeper::{Output, VoteKeeper};
+use informalsystems_malachitebft_core_votekeeper::Threshold;
 
 use malachitebft_test::{
     Address, Height, PrivateKey, Signature, TestContext, Validator, ValidatorSet, ValueId, Vote,
@@ -249,6 +250,30 @@ fn no_skip_round_full_quorum_with_same_val() {
     assert_eq!(msg, None);
 }
 
+#[test]
+fn skip_round_and_precommit_value_future_round() {
+    let ([addr1, addr2, ..], mut keeper) = setup([2, 3, 2]);
+
+    let id = ValueId::new(1);
+    let val = NilOrVal::Val(id);
+    let height = Height::new(1);
+    let cur_round = Round::new(0);
+    let fut_round = Round::new(1);
+
+    let vote = new_signed_precommit(height, fut_round, val, addr1);
+    let msg = keeper.apply_vote(vote, cur_round);
+    assert_eq!(msg, None);
+
+    let vote = new_signed_precommit(height, fut_round, val, addr2);
+    let msg = keeper.apply_vote(vote, cur_round);
+    assert_eq!(msg, Some(Output::SkipRound(fut_round)));
+
+    // A PrecommitValue(id) could be produced
+    assert!(keeper.is_threshold_met(&fut_round, VoteType::Precommit, Threshold::Value(id)));
+    // FIXME: should we instead expect it to be produced?
+    // assert_eq!(msg, Some(Output::PrecommitValue(id)));
+}
+
 #[test]
 fn same_votes() {
     let ([addr1, ..], mut keeper) = setup([1, 1]);