op-challenger: Simplify exposed API for dispute game proposals.

op-challenger/game/fault/contracts/faultdisputegame.go

@@ -36,12 +36,27 @@ type FaultDisputeGameContract struct {
 	contract    *batching.BoundContract
 }
 
-type Proposal struct {
+// contractProposal matches the structure for output root proposals used by the contracts.
+// It must exactly match the contract structure. The exposed API uses Proposal to decouple the contract
+// and challenger representations of the proposal data.
+type contractProposal struct {
 	Index         *big.Int
 	L2BlockNumber *big.Int
 	OutputRoot    common.Hash
 }
 
+type Proposal struct {
+	L2BlockNumber *big.Int
+	OutputRoot    common.Hash
+}
+
+func asProposal(p contractProposal) Proposal {
+	return Proposal{
+		L2BlockNumber: p.L2BlockNumber,
+		OutputRoot:    p.OutputRoot,
+	}
+}
+
 func NewFaultDisputeGameContract(addr common.Address, caller *batching.MultiCaller) (*FaultDisputeGameContract, error) {
 	fdgAbi, err := bindings.FaultDisputeGameMetaData.GetAbi()
 	if err != nil {
@@ -93,10 +108,10 @@ func (f *FaultDisputeGameContract) GetProposals(ctx context.Context) (Proposal,
 		return Proposal{}, Proposal{}, fmt.Errorf("failed to fetch proposals: %w", err)
 	}
 
-	var agreed, disputed Proposal
+	var agreed, disputed contractProposal
 	result.GetStruct(0, &agreed)
 	result.GetStruct(1, &disputed)
-	return agreed, disputed, nil
+	return asProposal(agreed), asProposal(disputed), nil
 }
 
 func (f *FaultDisputeGameContract) GetStatus(ctx context.Context) (gameTypes.GameStatus, error) {

op-challenger/game/fault/contracts/faultdisputegame_test.go

@@ -105,23 +105,31 @@ func TestGetProposals(t *testing.T) {
 	disputedIndex := big.NewInt(7)
 	disputedBlockNum := big.NewInt(8)
 	disputedRoot := common.Hash{0xdd}
-	agreed := Proposal{
+	agreed := contractProposal{
 		Index:         agreedIndex,
 		L2BlockNumber: agreedBlockNum,
 		OutputRoot:    agreedRoot,
 	}
-	disputed := Proposal{
+	disputed := contractProposal{
 		Index:         disputedIndex,
 		L2BlockNumber: disputedBlockNum,
 		OutputRoot:    disputedRoot,
 	}
+	expectedAgreed := Proposal{
+		L2BlockNumber: agreed.L2BlockNumber,
+		OutputRoot:    agreed.OutputRoot,
+	}
+	expectedDisputed := Proposal{
+		L2BlockNumber: disputed.L2BlockNumber,
+		OutputRoot:    disputed.OutputRoot,
+	}
 	stubRpc.SetResponse(fdgAddr, methodProposals, batching.BlockLatest, []interface{}{}, []interface{}{
 		agreed, disputed,
 	})
 	actualAgreed, actualDisputed, err := game.GetProposals(context.Background())
 	require.NoError(t, err)
-	require.Equal(t, agreed, actualAgreed)
-	require.Equal(t, disputed, actualDisputed)
+	require.Equal(t, expectedAgreed, actualAgreed)
+	require.Equal(t, expectedDisputed, actualDisputed)
 }
 
 func TestGetClaim(t *testing.T) {

op-challenger/game/fault/trace/cannon/local_test.go

@@ -17,12 +17,10 @@ func TestFetchLocalInputs(t *testing.T) {
 	contract := &mockGameInputsSource{
 		l1Head: common.Hash{0xcc},
 		starting: contracts.Proposal{
-			Index:         big.NewInt(6),
 			L2BlockNumber: big.NewInt(2222),
 			OutputRoot:    common.Hash{0xdd},
 		},
 		disputed: contracts.Proposal{
-			Index:         big.NewInt(7),
 			L2BlockNumber: big.NewInt(3333),
 			OutputRoot:    common.Hash{0xee},
 		},