accounts/abi/bind: add optional block number for calls

accounts/abi/bind/base.go

@@ -36,10 +36,10 @@ type SignerFn func(types.Signer, common.Address, *types.Transaction) (*types.Tra
 
 // CallOpts is the collection of options to fine tune a contract call request.
 type CallOpts struct {
-	Pending bool           // Whether to operate on the pending state or the last known one
-	From    common.Address // Optional the sender address, otherwise the first account is used
-
-	Context context.Context // Network context to support cancellation and timeouts (nil = no timeout)
+	Pending     bool            // Whether to operate on the pending state or the last known one
+	From        common.Address  // Optional the sender address, otherwise the first account is used
+	BlockNumber *big.Int        // Optional the block number on which the call should be performed
+	Context     context.Context // Network context to support cancellation and timeouts (nil = no timeout)
 }
 
 // TransactOpts is the collection of authorization data required to create a
@@ -148,10 +148,10 @@ func (c *BoundContract) Call(opts *CallOpts, result interface{}, method string,
 			}
 		}
 	} else {
-		output, err = c.caller.CallContract(ctx, msg, nil)
+		output, err = c.caller.CallContract(ctx, msg, opts.BlockNumber)
 		if err == nil && len(output) == 0 {
 			// Make sure we have a contract to operate on, and bail out otherwise.
-			if code, err = c.caller.CodeAt(ctx, c.address, nil); err != nil {
+			if code, err = c.caller.CodeAt(ctx, c.address, opts.BlockNumber); err != nil {
 				return err
 			} else if len(code) == 0 {
 				return ErrNoCode

accounts/abi/bind/base_test.go

@@ -0,0 +1,64 @@
+package bind_test
+
+import (
+	"context"
+	"math/big"
+	"testing"
+
+	ethereum "github.com/ethereum/go-ethereum"
+	"github.com/ethereum/go-ethereum/accounts/abi"
+	"github.com/ethereum/go-ethereum/accounts/abi/bind"
+	"github.com/ethereum/go-ethereum/common"
+)
+
+type mockCaller struct {
+	codeAtBlockNumber       *big.Int
+	callContractBlockNumber *big.Int
+}
+
+func (mc *mockCaller) CodeAt(ctx context.Context, contract common.Address, blockNumber *big.Int) ([]byte, error) {
+	mc.codeAtBlockNumber = blockNumber
+	return []byte{1, 2, 3}, nil
+}
+
+func (mc *mockCaller) CallContract(ctx context.Context, call ethereum.CallMsg, blockNumber *big.Int) ([]byte, error) {
+	mc.callContractBlockNumber = blockNumber
+	return nil, nil
+}
+
+func TestPassingBlockNumber(t *testing.T) {
+
+	mc := &mockCaller{}
+
+	bc := bind.NewBoundContract(common.HexToAddress("0x0"), abi.ABI{
+		Methods: map[string]abi.Method{
+			"something": {
+				Name:    "something",
+				Outputs: abi.Arguments{},
+			},
+		},
+	}, mc, nil, nil)
+	var ret string
+
+	blockNumber := big.NewInt(42)
+
+	bc.Call(&bind.CallOpts{BlockNumber: blockNumber}, &ret, "something")
+
+	if mc.callContractBlockNumber != blockNumber {
+		t.Fatalf("CallContract() was not passed the block number")
+	}
+
+	if mc.codeAtBlockNumber != blockNumber {
+		t.Fatalf("CodeAt() was not passed the block number")
+	}
+
+	bc.Call(&bind.CallOpts{}, &ret, "something")
+
+	if mc.callContractBlockNumber != nil {
+		t.Fatalf("CallContract() was passed a block number when it should not have been")
+	}
+
+	if mc.codeAtBlockNumber != nil {
+		t.Fatalf("CodeAt() was passed a block number when it should not have been")
+	}
+}