common: remove ToHex and ToHexArray (ethereum#21610)

ToHex was deprecated a couple years ago. The last remaining use
was in ToHexArray, which itself only had a single call site.

This just moves ToHexArray near its only remaining call site and
implements it using hexutil.Encode. This changes the default behaviour
of ToHexArray and with it the behaviour of eth_getProof. Previously we
encoded an empty slice as 0, now the empty slice is encoded as 0x.

common/bytes.go

@@ -17,28 +17,9 @@
 // Package common contains various helper functions.
 package common
 
-import "encoding/hex"
-
-// ToHex returns the hex representation of b, prefixed with '0x'.
-// For empty slices, the return value is "0x0".
-//
-// Deprecated: use hexutil.Encode instead.
-func ToHex(b []byte) string {
-	hex := Bytes2Hex(b)
-	if len(hex) == 0 {
-		hex = "0"
-	}
-	return "0x" + hex
-}
-
-// ToHexArray creates a array of hex-string based on []byte
-func ToHexArray(b [][]byte) []string {
-	r := make([]string, len(b))
-	for i := range b {
-		r[i] = ToHex(b[i])
-	}
-	return r
-}
+import (
+	"encoding/hex"
+)
 
 // FromHex returns the bytes represented by the hexadecimal string s.
 // s may be prefixed with "0x".

internal/ethapi/api.go

@@ -599,7 +599,7 @@ func (s *PublicBlockChainAPI) GetProof(ctx context.Context, address common.Addre
 			if storageError != nil {
 				return nil, storageError
 			}
-			storageProof[i] = StorageResult{key, (*hexutil.Big)(state.GetState(address, common.HexToHash(key)).Big()), common.ToHexArray(proof)}
+			storageProof[i] = StorageResult{key, (*hexutil.Big)(state.GetState(address, common.HexToHash(key)).Big()), toHexSlice(proof)}
 		} else {
 			storageProof[i] = StorageResult{key, &hexutil.Big{}, []string{}}
 		}
@@ -613,7 +613,7 @@ func (s *PublicBlockChainAPI) GetProof(ctx context.Context, address common.Addre
 
 	return &AccountResult{
 		Address:      address,
-		AccountProof: common.ToHexArray(accountProof),
+		AccountProof: toHexSlice(accountProof),
 		Balance:      (*hexutil.Big)(state.GetBalance(address)),
 		CodeHash:     codeHash,
 		Nonce:        hexutil.Uint64(state.GetNonce(address)),
@@ -1943,3 +1943,12 @@ func checkTxFee(gasPrice *big.Int, gas uint64, cap float64) error {
 	}
 	return nil
 }
+
+// toHexSlice creates a slice of hex-strings based on []byte.
+func toHexSlice(b [][]byte) []string {
+	r := make([]string, len(b))
+	for i := range b {
+		r[i] = hexutil.Encode(b[i])
+	}
+	return r
+}