add UnmarshalJSON for pgtype Numeric

pgtype/numeric.go

@@ -240,6 +240,18 @@ func (n Numeric) MarshalJSON() ([]byte, error) {
 	return n.numberTextBytes(), nil
 }
 
+func (n *Numeric) UnmarshalJSON(src []byte) error {
+	if bytes.Compare(src, []byte(`null`)) == 0 {
+		*n = Numeric{}
+		return nil
+	}
+	if bytes.Compare(src, []byte(`"NaN"`)) == 0 {
+		*n = Numeric{NaN: true, Valid: true}
+		return nil
+	}
+	return scanPlanTextAnyToNumericScanner{}.Scan(src, n)
+}
+
 // numberString returns a string of the number. undefined if NaN, infinite, or NULL
 func (n Numeric) numberTextBytes() []byte {
 	intStr := n.Int.String()

pgtype/numeric_test.go

@@ -6,6 +6,7 @@ import (
 	"math"
 	"math/big"
 	"math/rand"
+	"reflect"
 	"strconv"
 	"testing"
 
@@ -232,3 +233,72 @@ func TestNumericMarshalJSON(t *testing.T) {
 		}
 	})
 }
+
+func TestNumericUnmarshalJSON(t *testing.T) {
+	tests := []struct {
+		name    string
+		want    *pgtype.Numeric
+		src     []byte
+		wantErr bool
+	}{
+		{
+			name:    "null",
+			want:    &pgtype.Numeric{},
+			src:     []byte(`null`),
+			wantErr: false,
+		},
+		{
+			name:    "NaN",
+			want:    &pgtype.Numeric{Valid: true, NaN: true},
+			src:     []byte(`"NaN"`),
+			wantErr: false,
+		},
+		{
+			name:    "0",
+			want:    &pgtype.Numeric{Valid: true, Int: big.NewInt(0)},
+			src:     []byte("0"),
+			wantErr: false,
+		},
+		{
+			name:    "1",
+			want:    &pgtype.Numeric{Valid: true, Int: big.NewInt(1)},
+			src:     []byte("1"),
+			wantErr: false,
+		},
+		{
+			name:    "-1",
+			want:    &pgtype.Numeric{Valid: true, Int: big.NewInt(-1)},
+			src:     []byte("-1"),
+			wantErr: false,
+		},
+		{
+			name:    "bigInt",
+			want:    &pgtype.Numeric{Valid: true, Int: big.NewInt(1), Exp: 30},
+			src:     []byte("1000000000000000000000000000000"),
+			wantErr: false,
+		},
+		{
+			name:    "float: 1234.56789",
+			want:    &pgtype.Numeric{Valid: true, Int: big.NewInt(123456789), Exp: -5},
+			src:     []byte("1234.56789"),
+			wantErr: false,
+		},
+		{
+			name:    "invalid value",
+			want:    &pgtype.Numeric{},
+			src:     []byte("0xffff"),
+			wantErr: true,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := &pgtype.Numeric{}
+			if err := got.UnmarshalJSON(tt.src); (err != nil) != tt.wantErr {
+				t.Errorf("UnmarshalJSON() error = %v, wantErr %v", err, tt.wantErr)
+			}
+			if !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("UnmarshalJSON() got = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}