fix: Checkpoint lookup can return 0 voting weight

Author: djb15

solana/programs/staking/src/state/checkpoints.rs

@@ -311,6 +311,7 @@ pub fn find_checkpoint_le(
         let checkpoint = read_checkpoint_at_index(account_info, mid)?;
 
         if checkpoint.timestamp <= target_timestamp {
+            result = Some((mid, checkpoint));
             low = mid + 1;
         } else {
             high = mid;

solana/programs/staking/src/state/vote_weight_window_lengths.rs

@@ -150,6 +150,7 @@ pub fn find_window_length_le(
         let window_length = read_window_length_at_index(account_info, mid)?;
 
         if window_length.timestamp <= target_timestamp {
+            result = Some((mid, window_length));
             low = mid + 1;
         } else {
             high = mid;

solana/tests/api_test.ts

@@ -967,6 +967,47 @@ describe("api", async () => {
       assert.equal(abstainVotes.toString(), "22");
     });
 
+    it("should cast vote with the correct weight", async () => {
+      let stakeAccountCheckpointsAddress;
+      let proposalIdInput;
+
+      // Create 6 checkpoints, 1 second apart
+      for (let i = 0; i < 6; i++) {
+        stakeAccountCheckpointsAddress = await user3StakeConnection.delegate(
+          user3,
+          WHTokenBalance.fromString("50"),
+        );
+
+        // Create a proposal with a start time 10 seconds in the future in iteration 5
+        // We do this because the vote weight window is 10 seconds
+        if (i == 4) {
+          proposalIdInput = await addTestProposal(
+            user3StakeConnection,
+            Math.floor(Date.now() / 1000) + 10,
+          );
+        }
+
+        await sleep(1000);
+      }
+
+      await user3StakeConnection.castVote(
+        proposalIdInput,
+        new BN(10),
+        new BN(20),
+        new BN(12),
+        0,
+      );
+
+      const { proposalId, againstVotes, forVotes, abstainVotes } =
+        await user3StakeConnection.proposalVotes(proposalIdInput);
+
+      assert.equal(proposalId.toString("hex"), proposalIdInput.toString("hex"));
+      assert.equal(againstVotes.toString(), "10");
+      assert.equal(forVotes.toString(), "20");
+      assert.equal(abstainVotes.toString(), "12");
+
+    });
+
     it("should fail to castVote if next voter checkpoints are invalid", async () => {
       await sleep(1000);
       await user4StakeConnection.delegate(