fix(spanner): invalid numeric should throw an error

spanner/value.go

@@ -24,6 +24,7 @@ import (
 	"math/big"
 	"reflect"
 	"strconv"
+	"strings"
 	"time"
 
 	"cloud.google.com/go/civil"
@@ -56,6 +57,27 @@ func NumericString(r *big.Rat) string {
 	return r.FloatString(NumericScaleDigits)
 }
 
+// validateNumeric returns nil if there are no errors. It will return an error
+// when the numeric number is not valid.
+func validateNumeric(r *big.Rat) error {
+	// Add one more digit to the scale component to find out if there are more
+	// digits than required.
+	strRep := strings.TrimRight(r.FloatString(NumericScaleDigits+1), "0")
+	s := strings.Split(strRep, ".")
+	if len(s) != 2 {
+		return fmt.Errorf("invalid numeric float string: %s", strRep)
+	}
+	whole := s[0]
+	scale := s[1]
+	if len(scale) > NumericScaleDigits {
+		return fmt.Errorf("max scale for a numeric is %d. The requested numeric has more", NumericScaleDigits)
+	}
+	if len(whole) > NumericPrecisionDigits-NumericScaleDigits {
+		return fmt.Errorf("max precision for the whole component of a numeric is %d. The requested numeric has a whole component with precision %d", NumericPrecisionDigits-NumericScaleDigits, len(whole))
+	}
+	return nil
+}
+
 var (
 	// CommitTimestamp is a special value used to tell Cloud Spanner to insert
 	// the commit timestamp of the transaction into a column. It can be used in
@@ -2654,6 +2676,10 @@ func encodeValue(v interface{}) (*proto3.Value, *sppb.Type, error) {
 		pt = listType(floatType())
 	case big.Rat:
 		pb.Kind = stringKind(NumericString(&v))
+		err = validateNumeric(&v)
+		if err != nil {
+			return nil, nil, err
+		}
 		pt = numericType()
 	case []big.Rat:
 		if v != nil {
@@ -2680,6 +2706,10 @@ func encodeValue(v interface{}) (*proto3.Value, *sppb.Type, error) {
 		if v != nil {
 			pb.Kind = stringKind(NumericString(v))
 		}
+		err = validateNumeric(v)
+		if err != nil {
+			return nil, nil, err
+		}
 		pt = numericType()
 	case []*big.Rat:
 		if v != nil {

spanner/value_test.go

@@ -406,6 +406,37 @@ func TestEncodeValue(t *testing.T) {
 	}
 }
 
+// Test encoding invalid values.
+func TestEncodeInvalidValues(t *testing.T) {
+	type CustomNumeric big.Rat
+
+	invalidNumPtr1 := big.NewRat(11234567891, 1e10)
+	invalidNumPtr2, _ := (&big.Rat{}).SetString("199999999999999999999999999999.999999999")
+
+	for i, test := range []struct {
+		desc   string
+		in     interface{}
+		errMsg string
+	}{
+		// NUMERIC
+		{desc: "numeric pointer with invalid scale component", in: invalidNumPtr1, errMsg: "max scale for a numeric is 9. The requested numeric has more"},
+		{desc: "numeric pointer with invalid whole component", in: invalidNumPtr2, errMsg: "max precision for the whole component of a numeric is 29. The requested numeric has a whole component with precision 30"},
+		{desc: "numeric with invalid scale component", in: *invalidNumPtr1, errMsg: "max scale for a numeric is 9. The requested numeric has more"},
+		{desc: "numeric with invalid whole component", in: *invalidNumPtr2, errMsg: "max precision for the whole component of a numeric is 29. The requested numeric has a whole component with precision 30"},
+		// CUSTOM NUMERIC
+		{desc: "custom numeric type with invalid scale component", in: CustomNumeric(*invalidNumPtr1), errMsg: "max scale for a numeric is 9. The requested numeric has more"},
+		{desc: "custom numeric type with invalid whole component", in: CustomNumeric(*invalidNumPtr2), errMsg: "max precision for the whole component of a numeric is 29. The requested numeric has a whole component with precision 30"},
+	} {
+		_, _, err := encodeValue(test.in)
+		if err == nil {
+			t.Fatalf("#%d (%s): want error during encoding, but got nil", i, test.desc)
+		}
+		if err.Error() != test.errMsg {
+			t.Errorf("#%d (%s): incorrect error message, got %v, want %v", i, test.desc, err, test.errMsg)
+		}
+	}
+}
+
 type encodeTest struct {
 	desc     string
 	in       interface{}