common: Fix NumericToBigInt returning zero for negative exponents

.changelog/1230.bugfix.1.md

@@ -0,0 +1,5 @@
+analyzer/runtime: Fix pointer comparison in balance update check
+
+The condition `change != big.NewInt(0)` was comparing pointers instead
+of values, causing it to always be true. Changed to `change.Sign() != 0`
+for proper value comparison.

.changelog/1230.bugfix.2.md

@@ -0,0 +1,5 @@
+common: Fix NumericToBigInt returning zero for negative exponents
+
+The function was returning `*big0` instead of `*bi` for negative
+exponents, causing it to always return zero. Added tests for the
+function.

analyzer/runtime/runtime.go

@@ -617,7 +617,7 @@ func (m *processor) queueDbUpdates(batch *storage.QueryBatch, data *BlockData) {
 	// Update EVM token balances (dead reckoning).
 	for key, change := range data.TokenBalanceChanges {
 		// Update (dead-reckon) the DB balance only if it's actually changed.
-		if change != big.NewInt(0) && m.mode != analyzer.FastSyncMode {
+		if change.Sign() != 0 && m.mode != analyzer.FastSyncMode {
 			if key.TokenAddress == evm.NativeRuntimeTokenAddress {
 				batch.Queue(queries.RuntimeNativeBalanceUpsert, m.runtime, key.AccountAddress, nativeTokenSymbol(m.sdkPT), change.String())
 			} else {

common/types.go

@@ -168,9 +168,9 @@ func NumericToBigInt(n pgtype.Numeric) (BigInt, error) {
 	remainder := &big.Int{}
 	bi.DivMod(bi, div, remainder)
 	if remainder.Cmp(big0) != 0 {
-		return BigInt{Int: *big0}, fmt.Errorf("cannot convert %v to integer", n)
+		return BigInt{}, fmt.Errorf("cannot convert %v to integer", n)
 	}
-	return BigInt{Int: *big0}, nil
+	return BigInt{Int: *bi}, nil
 }
 
 // Decimal is a wrapper around apd.Decimal to allow for custom JSON marshaling.

common/types_test.go

@@ -4,8 +4,10 @@ import (
 	"encoding/json"
 	"fmt"
 	"math"
+	"math/big"
 	"testing"
 
+	"github.com/jackc/pgx/v5/pgtype"
 	"github.com/oasisprotocol/oasis-core/go/common/cbor"
 	"github.com/stretchr/testify/require"
 )
@@ -122,3 +124,53 @@ func TestBigDecimalNumeric(t *testing.T) {
 		require.EqualValues(t, dec, roundTripped, "BigDecimal should match after Numeric conversion for value %s", tc.value)
 	}
 }
+
+func TestNumericToBigInt(t *testing.T) {
+	for _, tc := range []struct {
+		name     string
+		numeric  pgtype.Numeric
+		expected int64
+		hasError bool
+	}{
+		{
+			name:     "zero exponent",
+			numeric:  pgtype.Numeric{Int: big.NewInt(12345), Exp: 0, Valid: true},
+			expected: 12345,
+		},
+		{
+			name:     "positive exponent",
+			numeric:  pgtype.Numeric{Int: big.NewInt(123), Exp: 2, Valid: true},
+			expected: 12300,
+		},
+		{
+			name:     "negative exponent exact division",
+			numeric:  pgtype.Numeric{Int: big.NewInt(12300), Exp: -2, Valid: true},
+			expected: 123,
+		},
+		{
+			name:     "negative exponent with remainder",
+			numeric:  pgtype.Numeric{Int: big.NewInt(12345), Exp: -2, Valid: true},
+			hasError: true,
+		},
+		{
+			name:     "zero value",
+			numeric:  pgtype.Numeric{Int: big.NewInt(0), Exp: 0, Valid: true},
+			expected: 0,
+		},
+		{
+			name:     "negative value",
+			numeric:  pgtype.Numeric{Int: big.NewInt(-500), Exp: 1, Valid: true},
+			expected: -5000,
+		},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			result, err := NumericToBigInt(tc.numeric)
+			if tc.hasError {
+				require.Error(t, err)
+			} else {
+				require.NoError(t, err)
+				require.Equal(t, tc.expected, result.Int64())
+			}
+		})
+	}
+}