common: improve printing of Hash and Address (#21834)

Both Hash and Address have a String method, which returns the value as
hex with 0x prefix. They also had a Format method which tried to print
the value using printf of []byte. The way Format worked was at odds with
String though, leading to a situation where fmt.Sprintf("%v", hash)
returned the decimal notation and hash.String() returned a hex string.

This commit makes it consistent again. Both types now support the %v,
%s, %q format verbs for 0x-prefixed hex output. %x, %X creates
unprefixed hex output. %d is also supported and returns the decimal
notation "[1 2 3...]".

For Address, the case of hex characters in %v, %s, %q output is
determined using the EIP-55 checksum. Using %x, %X with Address
disables checksumming.

Co-authored-by: Felix Lange <fjl@twurst.com>

common/types.go

@@ -17,6 +17,7 @@
 package common
 
 import (
+	"bytes"
 	"database/sql/driver"
 	"encoding/hex"
 	"encoding/json"
@@ -84,10 +85,34 @@ func (h Hash) String() string {
 	return h.Hex()
 }
 
-// Format implements fmt.Formatter, forcing the byte slice to be formatted as is,
+// Format implements fmt.Formatter.
-// without going through the stringer interface used for logging.
+// Hash supports the %v, %s, %v, %x, %X and %d format verbs.
 func (h Hash) Format(s fmt.State, c rune) {
-	fmt.Fprintf(s, "%"+string(c), h[:])
+	hexb := make([]byte, 2+len(h)*2)
+	copy(hexb, "0x")
+	hex.Encode(hexb[2:], h[:])
+
+	switch c {
+	case 'x', 'X':
+		if !s.Flag('#') {
+			hexb = hexb[2:]
+		}
+		if c == 'X' {
+			hexb = bytes.ToUpper(hexb)
+		}
+		fallthrough
+	case 'v', 's':
+		s.Write(hexb)
+	case 'q':
+		q := []byte{'"'}
+		s.Write(q)
+		s.Write(hexb)
+		s.Write(q)
+	case 'd':
+		fmt.Fprint(s, ([len(h)]byte)(h))
+	default:
+		fmt.Fprintf(s, "%%!%c(hash=%x)", c, h)
+	}
 }
 
 // UnmarshalText parses a hash in hex syntax.
@@ -208,35 +233,68 @@ func (a Address) Hash() Hash { return BytesToHash(a[:]) }
 
 // Hex returns an EIP55-compliant hex string representation of the address.
 func (a Address) Hex() string {
-	unchecksummed := hex.EncodeToString(a[:])
+	return string(a.checksumHex())
+}
+
+// String implements fmt.Stringer.
+func (a Address) String() string {
+	return a.Hex()
+}
+
+func (a *Address) checksumHex() []byte {
+	buf := a.hex()
+
+	// compute checksum
 	sha := sha3.NewLegacyKeccak256()
-	sha.Write([]byte(unchecksummed))
+	sha.Write(buf[2:])
 	hash := sha.Sum(nil)
-
+	for i := 2; i < len(buf); i++ {
-	result := []byte(unchecksummed)
+		hashByte := hash[(i-2)/2]
-	for i := 0; i < len(result); i++ {
-		hashByte := hash[i/2]
 		if i%2 == 0 {
 			hashByte = hashByte >> 4
 		} else {
 			hashByte &= 0xf
 		}
-		if result[i] > '9' && hashByte > 7 {
+		if buf[i] > '9' && hashByte > 7 {
-			result[i] -= 32
+			buf[i] -= 32
 		}
 	}
-	return "0x" + string(result)
+	return buf[:]
 }
 
-// String implements fmt.Stringer.
+func (a Address) hex() []byte {
-func (a Address) String() string {
+	var buf [len(a)*2 + 2]byte
-	return a.Hex()
+	copy(buf[:2], "0x")
+	hex.Encode(buf[2:], a[:])
+	return buf[:]
 }
 
-// Format implements fmt.Formatter, forcing the byte slice to be formatted as is,
+// Format implements fmt.Formatter.
-// without going through the stringer interface used for logging.
+// Address supports the %v, %s, %v, %x, %X and %d format verbs.
 func (a Address) Format(s fmt.State, c rune) {
-	fmt.Fprintf(s, "%"+string(c), a[:])
+	switch c {
+	case 'v', 's':
+		s.Write(a.checksumHex())
+	case 'q':
+		q := []byte{'"'}
+		s.Write(q)
+		s.Write(a.checksumHex())
+		s.Write(q)
+	case 'x', 'X':
+		// %x disables the checksum.
+		hex := a.hex()
+		if !s.Flag('#') {
+			hex = hex[2:]
+		}
+		if c == 'X' {
+			hex = bytes.ToUpper(hex)
+		}
+		s.Write(hex)
+	case 'd':
+		fmt.Fprint(s, ([len(a)]byte)(a))
+	default:
+		fmt.Fprintf(s, "%%!%c(address=%x)", c, a)
+	}
 }
 
 // SetBytes sets the address to the value of b.

common/types_test.go

@@ -17,8 +17,10 @@
 package common
 
 import (
+	"bytes"
 	"database/sql/driver"
 	"encoding/json"
+	"fmt"
 	"math/big"
 	"reflect"
 	"strings"
@@ -371,3 +373,167 @@ func TestAddress_Value(t *testing.T) {
 		})
 	}
 }
+
+func TestAddress_Format(t *testing.T) {
+	b := []byte{
+		0xb2, 0x6f, 0x2b, 0x34, 0x2a, 0xab, 0x24, 0xbc, 0xf6, 0x3e,
+		0xa2, 0x18, 0xc6, 0xa9, 0x27, 0x4d, 0x30, 0xab, 0x9a, 0x15,
+	}
+	var addr Address
+	addr.SetBytes(b)
+
+	tests := []struct {
+		name string
+		out  string
+		want string
+	}{
+		{
+			name: "println",
+			out:  fmt.Sprintln(addr),
+			want: "0xB26f2b342AAb24BCF63ea218c6A9274D30Ab9A15\n",
+		},
+		{
+			name: "print",
+			out:  fmt.Sprint(addr),
+			want: "0xB26f2b342AAb24BCF63ea218c6A9274D30Ab9A15",
+		},
+		{
+			name: "printf-s",
+			out: func() string {
+				buf := new(bytes.Buffer)
+				fmt.Fprintf(buf, "%s", addr)
+				return buf.String()
+			}(),
+			want: "0xB26f2b342AAb24BCF63ea218c6A9274D30Ab9A15",
+		},
+		{
+			name: "printf-q",
+			out:  fmt.Sprintf("%q", addr),
+			want: `"0xB26f2b342AAb24BCF63ea218c6A9274D30Ab9A15"`,
+		},
+		{
+			name: "printf-x",
+			out:  fmt.Sprintf("%x", addr),
+			want: "b26f2b342aab24bcf63ea218c6a9274d30ab9a15",
+		},
+		{
+			name: "printf-X",
+			out:  fmt.Sprintf("%X", addr),
+			want: "B26F2B342AAB24BCF63EA218C6A9274D30AB9A15",
+		},
+		{
+			name: "printf-#x",
+			out:  fmt.Sprintf("%#x", addr),
+			want: "0xb26f2b342aab24bcf63ea218c6a9274d30ab9a15",
+		},
+		{
+			name: "printf-v",
+			out:  fmt.Sprintf("%v", addr),
+			want: "0xB26f2b342AAb24BCF63ea218c6A9274D30Ab9A15",
+		},
+		// The original default formatter for byte slice
+		{
+			name: "printf-d",
+			out:  fmt.Sprintf("%d", addr),
+			want: "[178 111 43 52 42 171 36 188 246 62 162 24 198 169 39 77 48 171 154 21]",
+		},
+		// Invalid format char.
+		{
+			name: "printf-t",
+			out:  fmt.Sprintf("%t", addr),
+			want: "%!t(address=b26f2b342aab24bcf63ea218c6a9274d30ab9a15)",
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if tt.out != tt.want {
+				t.Errorf("%s does not render as expected:\n got %s\nwant %s", tt.name, tt.out, tt.want)
+			}
+		})
+	}
+}
+
+func TestHash_Format(t *testing.T) {
+	var hash Hash
+	hash.SetBytes([]byte{
+		0xb2, 0x6f, 0x2b, 0x34, 0x2a, 0xab, 0x24, 0xbc, 0xf6, 0x3e,
+		0xa2, 0x18, 0xc6, 0xa9, 0x27, 0x4d, 0x30, 0xab, 0x9a, 0x15,
+		0xa2, 0x18, 0xc6, 0xa9, 0x27, 0x4d, 0x30, 0xab, 0x9a, 0x15,
+		0x10, 0x00,
+	})
+
+	tests := []struct {
+		name string
+		out  string
+		want string
+	}{
+		{
+			name: "println",
+			out:  fmt.Sprintln(hash),
+			want: "0xb26f2b342aab24bcf63ea218c6a9274d30ab9a15a218c6a9274d30ab9a151000\n",
+		},
+		{
+			name: "print",
+			out:  fmt.Sprint(hash),
+			want: "0xb26f2b342aab24bcf63ea218c6a9274d30ab9a15a218c6a9274d30ab9a151000",
+		},
+		{
+			name: "printf-s",
+			out: func() string {
+				buf := new(bytes.Buffer)
+				fmt.Fprintf(buf, "%s", hash)
+				return buf.String()
+			}(),
+			want: "0xb26f2b342aab24bcf63ea218c6a9274d30ab9a15a218c6a9274d30ab9a151000",
+		},
+		{
+			name: "printf-q",
+			out:  fmt.Sprintf("%q", hash),
+			want: `"0xb26f2b342aab24bcf63ea218c6a9274d30ab9a15a218c6a9274d30ab9a151000"`,
+		},
+		{
+			name: "printf-x",
+			out:  fmt.Sprintf("%x", hash),
+			want: "b26f2b342aab24bcf63ea218c6a9274d30ab9a15a218c6a9274d30ab9a151000",
+		},
+		{
+			name: "printf-X",
+			out:  fmt.Sprintf("%X", hash),
+			want: "B26F2B342AAB24BCF63EA218C6A9274D30AB9A15A218C6A9274D30AB9A151000",
+		},
+		{
+			name: "printf-#x",
+			out:  fmt.Sprintf("%#x", hash),
+			want: "0xb26f2b342aab24bcf63ea218c6a9274d30ab9a15a218c6a9274d30ab9a151000",
+		},
+		{
+			name: "printf-#X",
+			out:  fmt.Sprintf("%#X", hash),
+			want: "0XB26F2B342AAB24BCF63EA218C6A9274D30AB9A15A218C6A9274D30AB9A151000",
+		},
+		{
+			name: "printf-v",
+			out:  fmt.Sprintf("%v", hash),
+			want: "0xb26f2b342aab24bcf63ea218c6a9274d30ab9a15a218c6a9274d30ab9a151000",
+		},
+		// The original default formatter for byte slice
+		{
+			name: "printf-d",
+			out:  fmt.Sprintf("%d", hash),
+			want: "[178 111 43 52 42 171 36 188 246 62 162 24 198 169 39 77 48 171 154 21 162 24 198 169 39 77 48 171 154 21 16 0]",
+		},
+		// Invalid format char.
+		{
+			name: "printf-t",
+			out:  fmt.Sprintf("%t", hash),
+			want: "%!t(hash=b26f2b342aab24bcf63ea218c6a9274d30ab9a15a218c6a9274d30ab9a151000)",
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if tt.out != tt.want {
+				t.Errorf("%s does not render as expected:\n got %s\nwant %s", tt.name, tt.out, tt.want)
+			}
+		})
+	}
+}