Update Simulated Backend Client (#10403)

* Update Simulated Backend Client

This commit aims to improve the simulated backend client by removing the block
limit where only the latest block can be provided to `CallContext` and handling
input args more gracefully.

- `CallContext` will now only validate the block number passed in args
- `CallContext` will NOT restrict calls to current block, but will pass nil to backend
- `from` in call args is no longer required and will default to `0x`
- `from` and `to` accept `common.Address`, `*big.Int` and `string` types

Included is a move to Go standard error handling consistent with v1.20+ and
error wrapping.

* remove commented code

* add comments at top of file and panic on unrecognized value type

* updated error handling and comments

* address comments

core/chains/evm/client/doc.go

@@ -0,0 +1,10 @@
+/*
+The simulated backend cannot access old blocks and will return an error if
+anything other than `latest`, `nil`, or the latest block are passed to
+`CallContract`.
+
+The simulated client avoids the old block error from the simulated backend by
+passing `nil` to `CallContract` when calling `CallContext` or `BatchCallContext`
+and will not return an error when an old block is used.
+*/
+package client

core/chains/evm/client/simulated_backend_client.go

@@ -3,6 +3,7 @@ package client
 import (
 	"bytes"
 	"context"
+	"errors"
 	"fmt"
 	"math/big"
 	"strings"
@@ -16,7 +17,6 @@ import (
 	"github.com/ethereum/go-ethereum/common/hexutil"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/rpc"
-	"github.com/pkg/errors"
 
 	clienttypes "github.com/smartcontractkit/chainlink/v2/common/chains/client"
 	"github.com/smartcontractkit/chainlink/v2/core/assets"
@@ -64,37 +64,85 @@ func (c *SimulatedBackendClient) checkEthCallArgs(
 			"must be an eth.CallArgs, got %+#v", args[0])
 	}
 	blockNumber, err := c.blockNumber(args[1])
-	if err != nil || blockNumber.Cmp(c.currentBlockNumber()) != 0 {
+	if err != nil {
 		return nil, nil, fmt.Errorf("fourth arg to SimulatedBackendClient.Call "+
-			"must be the string \"latest\", or a *big.Int equal to current "+
-			"blocknumber, got %#+v", args[1])
+			"must be the string \"latest\", or a *big.Int, got %#+v", args[1])
 	}
+
+	// to and from need to map to a common.Address but could come in as a string
+	var (
+		toAddr  common.Address
+		frmAddr common.Address
+	)
+
+	toAddr, err = interfaceToAddress(callArgs["to"])
+	if err != nil {
+		return nil, nil, err
+	}
+
+	// from is optional in the standard client; default to 0x when missing
+	if value, ok := callArgs["from"]; ok {
+		addr, err := interfaceToAddress(value)
+		if err != nil {
+			return nil, nil, err
+		}
+
+		frmAddr = addr
+	} else {
+		frmAddr = common.HexToAddress("0x")
+	}
+
 	ca := CallArgs{
-		From: callArgs["from"].(common.Address),
-		To:   *callArgs["to"].(*common.Address),
+		To:   toAddr,
+		From: frmAddr,
 		Data: callArgs["data"].(hexutil.Bytes),
 	}
+
 	return &ca, blockNumber, nil
 }
 
+func interfaceToAddress(value interface{}) (common.Address, error) {
+	switch v := value.(type) {
+	case common.Address:
+		return v, nil
+	case string:
+		return common.HexToAddress(v), nil
+	case *big.Int:
+		return common.BigToAddress(v), nil
+	default:
+		return common.HexToAddress("0x"), fmt.Errorf("unrecognized value type for converting value to common.Address; try string, *big.Int, or common.Address")
+	}
+}
+
 // CallContext mocks the ethereum client RPC calls used by chainlink, copying the
 // return value into result.
+// The simulated client avoids the old block error from the simulated backend by
+// passing `nil` to `CallContract` when calling `CallContext` or `BatchCallContext`
+// and will not return an error when an old block is used.
 func (c *SimulatedBackendClient) CallContext(ctx context.Context, result interface{}, method string, args ...interface{}) error {
 	switch method {
 	case "eth_call":
-		callArgs, _, err := c.checkEthCallArgs(args)
-		if err != nil {
+		var (
+			callArgs *CallArgs
+			b        []byte
+			err      error
+		)
+
+		if callArgs, _, err = c.checkEthCallArgs(args); err != nil {
 			return err
 		}
+
 		callMsg := ethereum.CallMsg{From: callArgs.From, To: &callArgs.To, Data: callArgs.Data}
-		b, err := c.b.CallContract(ctx, callMsg, nil /* always latest block */)
-		if err != nil {
-			return errors.Wrapf(err, "while calling contract at address %x with "+
-				"data %x", callArgs.To, callArgs.Data)
+
+		if b, err = c.b.CallContract(ctx, callMsg, nil /* always latest block */); err != nil {
+			return fmt.Errorf("%w: while calling contract at address %x with "+
+				"data %x", err, callArgs.To, callArgs.Data)
 		}
+
 		switch r := result.(type) {
 		case *hexutil.Bytes:
 			*r = append(*r, b...)
+
 			if !bytes.Equal(*r, b) {
 				return fmt.Errorf("was passed a non-empty array, or failed to copy "+
 					"answer. Expected %x = %x", *r, b)
@@ -155,26 +203,26 @@ func init() {
 	var err error
 	balanceOfABI, err = abi.JSON(strings.NewReader(balanceOfABIString))
 	if err != nil {
-		panic(errors.Wrapf(err, "while parsing erc20ABI"))
+		panic(fmt.Errorf("%w: while parsing erc20ABI", err))
 	}
 }
 
 func (c *SimulatedBackendClient) TokenBalance(ctx context.Context, address common.Address, contractAddress common.Address) (balance *big.Int, err error) {
 	callData, err := balanceOfABI.Pack("balanceOf", address)
 	if err != nil {
-		return nil, errors.Wrapf(err, "while seeking the ERC20 balance of %s on %s",
+		return nil, fmt.Errorf("%w: while seeking the ERC20 balance of %s on %s", err,
 			address, contractAddress)
 	}
 	b, err := c.b.CallContract(ctx, ethereum.CallMsg{
 		To: &contractAddress, Data: callData},
 		c.currentBlockNumber())
 	if err != nil {
-		return nil, errors.Wrapf(err, "while calling ERC20 balanceOf method on %s "+
-			"for balance of %s", contractAddress, address)
+		return nil, fmt.Errorf("%w: while calling ERC20 balanceOf method on %s "+
+			"for balance of %s", err, contractAddress, address)
 	}
 	err = balanceOfABI.UnpackIntoInterface(balance, "balanceOf", b)
 	if err != nil {
-		return nil, errors.New("unable to unpack balance")
+		return nil, fmt.Errorf("unable to unpack balance")
 	}
 	return balance, nil
 }
@@ -208,8 +256,8 @@ func (c *SimulatedBackendClient) blockNumber(number interface{}) (blockNumber *b
 		default:
 			blockNumber, err = utils.HexToUint256(n)
 			if err != nil {
-				return nil, errors.Wrapf(err, "while parsing '%s' as hex-encoded"+
-					"block number", n)
+				return nil, fmt.Errorf("%w: while parsing '%s' as hex-encoded"+
+					"block number", err, n)
 			}
 			return blockNumber, nil
 		}
@@ -328,8 +376,8 @@ func (c *SimulatedBackendClient) SubscribeNewHead(
 	var err error
 	subscription.subscription, err = c.b.SubscribeNewHead(ctx, ch)
 	if err != nil {
-		return nil, errors.Wrapf(err, "could not subscribe to new heads on "+
-			"simulated backend")
+		return nil, fmt.Errorf("%w: could not subscribe to new heads on "+
+			"simulated backend", err)
 	}
 	go func() {
 		var lastHead *evmtypes.Head
@@ -428,8 +476,7 @@ func (c *SimulatedBackendClient) CallContract(ctx context.Context, msg ethereum.
 	res, err := c.b.CallContract(ctx, msg, blockNumber)
 	if err != nil {
 		dataErr := revertError{}
-		isCustomRevert := errors.As(err, &dataErr)
-		if isCustomRevert {
+		if errors.Is(err, &dataErr) {
 			return nil, &JsonError{Data: dataErr.ErrorData(), Message: dataErr.Error(), Code: 3}
 		}
 		// Generic revert, no data
@@ -459,6 +506,9 @@ func (c *SimulatedBackendClient) SuggestGasPrice(ctx context.Context) (*big.Int,
 }
 
 // BatchCallContext makes a batch rpc call.
+// The simulated client avoids the old block error from the simulated backend by
+// passing `nil` to `CallContract` when calling `CallContext` or `BatchCallContext`
+// and will not return an error when an old block is used.
 func (c *SimulatedBackendClient) BatchCallContext(ctx context.Context, b []rpc.BatchElem) error {
 	select {
 	case <-ctx.Done():
@@ -471,14 +521,14 @@ func (c *SimulatedBackendClient) BatchCallContext(ctx context.Context, b []rpc.B
 		switch elem.Method {
 		case "eth_getTransactionReceipt":
 			if _, ok := elem.Result.(*evmtypes.Receipt); !ok {
-				return errors.Errorf("SimulatedBackendClient expected return type of *evmtypes.Receipt for eth_getTransactionReceipt, got type %T", elem.Result)
+				return fmt.Errorf("SimulatedBackendClient expected return type of *evmtypes.Receipt for eth_getTransactionReceipt, got type %T", elem.Result)
 			}
 			if len(elem.Args) != 1 {
-				return errors.Errorf("SimulatedBackendClient expected 1 arg, got %d for eth_getTransactionReceipt", len(elem.Args))
+				return fmt.Errorf("SimulatedBackendClient expected 1 arg, got %d for eth_getTransactionReceipt", len(elem.Args))
 			}
 			hash, is := elem.Args[0].(common.Hash)
 			if !is {
-				return errors.Errorf("SimulatedBackendClient expected arg to be a hash, got: %T", elem.Args[0])
+				return fmt.Errorf("SimulatedBackendClient expected arg to be a hash, got: %T", elem.Args[0])
 			}
 			receipt, err := c.b.TransactionReceipt(ctx, hash)
 			if receipt != nil {
@@ -490,22 +540,22 @@ func (c *SimulatedBackendClient) BatchCallContext(ctx context.Context, b []rpc.B
 			case *evmtypes.Head:
 			case *evmtypes.Block:
 			default:
-				return errors.Errorf("SimulatedBackendClient expected return type of [*evmtypes.Head] or [*evmtypes.Block] for eth_getBlockByNumber, got type %T", v)
+				return fmt.Errorf("SimulatedBackendClient expected return type of [*evmtypes.Head] or [*evmtypes.Block] for eth_getBlockByNumber, got type %T", v)
 			}
 			if len(elem.Args) != 2 {
-				return errors.Errorf("SimulatedBackendClient expected 2 args, got %d for eth_getBlockByNumber", len(elem.Args))
+				return fmt.Errorf("SimulatedBackendClient expected 2 args, got %d for eth_getBlockByNumber", len(elem.Args))
 			}
 			blockNum, is := elem.Args[0].(string)
 			if !is {
-				return errors.Errorf("SimulatedBackendClient expected first arg to be a string for eth_getBlockByNumber, got: %T", elem.Args[0])
+				return fmt.Errorf("SimulatedBackendClient expected first arg to be a string for eth_getBlockByNumber, got: %T", elem.Args[0])
 			}
 			_, is = elem.Args[1].(bool)
 			if !is {
-				return errors.Errorf("SimulatedBackendClient expected second arg to be a boolean for eth_getBlockByNumber, got: %T", elem.Args[1])
+				return fmt.Errorf("SimulatedBackendClient expected second arg to be a boolean for eth_getBlockByNumber, got: %T", elem.Args[1])
 			}
 			n, ok := new(big.Int).SetString(blockNum, 0)
 			if !ok {
-				return errors.Errorf("error while converting block number string: %s to big.Int ", blockNum)
+				return fmt.Errorf("error while converting block number string: %s to big.Int ", blockNum)
 			}
 			header, err := c.b.HeaderByNumber(ctx, n)
 			if err != nil {
@@ -525,33 +575,33 @@ func (c *SimulatedBackendClient) BatchCallContext(ctx context.Context, b []rpc.B
 					Timestamp: time.Unix(int64(header.Time), 0),
 				}
 			default:
-				return errors.Errorf("SimulatedBackendClient Unexpected Type %T", v)
+				return fmt.Errorf("SimulatedBackendClient Unexpected Type %T", v)
 			}
 
 			b[i].Error = err
 		case "eth_call":
 			if len(elem.Args) != 2 {
-				return errors.Errorf("SimulatedBackendClient expected 2 args, got %d for eth_call", len(elem.Args))
+				return fmt.Errorf("SimulatedBackendClient expected 2 args, got %d for eth_call", len(elem.Args))
 			}
 
 			_, ok := elem.Result.(*string)
 			if !ok {
-				return errors.Errorf("SimulatedBackendClient expected result to be *string for eth_call, got: %T", elem.Result)
+				return fmt.Errorf("SimulatedBackendClient expected result to be *string for eth_call, got: %T", elem.Result)
 			}
 
 			params, ok := elem.Args[0].(map[string]interface{})
 			if !ok {
-				return errors.Errorf("SimulatedBackendClient expected first arg to be map[string]interface{} for eth_call, got: %T", elem.Args[0])
+				return fmt.Errorf("SimulatedBackendClient expected first arg to be map[string]interface{} for eth_call, got: %T", elem.Args[0])
 			}
 
 			blockNum, ok := elem.Args[1].(string)
 			if !ok {
-				return errors.Errorf("SimulatedBackendClient expected second arg to be a string for eth_call, got: %T", elem.Args[1])
+				return fmt.Errorf("SimulatedBackendClient expected second arg to be a string for eth_call, got: %T", elem.Args[1])
 			}
 
 			if blockNum != "" {
 				if _, ok = new(big.Int).SetString(blockNum, 0); !ok {
-					return errors.Errorf("error while converting block number string: %s to big.Int ", blockNum)
+					return fmt.Errorf("error while converting block number string: %s to big.Int ", blockNum)
 				}
 			}
 
@@ -561,15 +611,15 @@ func (c *SimulatedBackendClient) BatchCallContext(ctx context.Context, b []rpc.B
 			b[i].Error = err
 		case "eth_getHeaderByNumber":
 			if len(elem.Args) != 1 {
-				return errors.Errorf("SimulatedBackendClient expected 2 args, got %d for eth_getHeaderByNumber", len(elem.Args))
+				return fmt.Errorf("SimulatedBackendClient expected 2 args, got %d for eth_getHeaderByNumber", len(elem.Args))
 			}
 			blockNum, is := elem.Args[0].(string)
 			if !is {
-				return errors.Errorf("SimulatedBackendClient expected first arg to be a string for eth_getHeaderByNumber, got: %T", elem.Args[0])
+				return fmt.Errorf("SimulatedBackendClient expected first arg to be a string for eth_getHeaderByNumber, got: %T", elem.Args[0])
 			}
 			n, err := hexutil.DecodeBig(blockNum)
 			if err != nil {
-				return errors.Errorf("error while converting hex block number %s to big.Int ", blockNum)
+				return fmt.Errorf("error while converting hex block number %s to big.Int ", blockNum)
 			}
 			header, err := c.b.HeaderByNumber(ctx, n)
 			if err != nil {
@@ -579,10 +629,10 @@ func (c *SimulatedBackendClient) BatchCallContext(ctx context.Context, b []rpc.B
 			case *types.Header:
 				b[i].Result = header
 			default:
-				return errors.Errorf("SimulatedBackendClient Unexpected Type %T", v)
+				return fmt.Errorf("SimulatedBackendClient Unexpected Type %T", v)
 			}
 		default:
-			return errors.Errorf("SimulatedBackendClient got unsupported method %s", elem.Method)
+			return fmt.Errorf("SimulatedBackendClient got unsupported method %s", elem.Method)
 		}
 	}
 	return nil