feat(math): add mutative api for LegacyDec.BigInt() (#18421)

math/CHANGELOG.md

@@ -36,6 +36,10 @@ Ref: https://github.com/commitizen/conventional-commit-types/blob/v3.0.0/index.j
 
 ## [Unreleased]
 
+### Features
+
+* [#18421](https://github.com/cosmos/cosmos-sdk/pull/18421) Add mutative api for `LegacyDec.BigInt()`.
+
 ## [math/v1.2.0](https://github.com/cosmos/cosmos-sdk/releases/tag/math/v1.2.0) - 2023-11-07
 
 ### Features

math/dec.go

@@ -235,6 +235,15 @@ func (d LegacyDec) BigInt() *big.Int {
 	return cp.Set(d.i)
 }
 
+// BigIntMut converts LegacyDec to big.Int, mutative the input
+func (d LegacyDec) BigIntMut() *big.Int {
+	if d.IsNil() {
+		return nil
+	}
+
+	return d.i
+}
+
 func (d LegacyDec) ImmutOp(op func(LegacyDec, LegacyDec) LegacyDec, d2 LegacyDec) LegacyDec {
 	return op(d.Clone(), d2)
 }

math/dec_test.go

@@ -754,3 +754,23 @@ func TestNegativePrecisionPanic(t *testing.T) {
 		math.LegacyNewDecWithPrec(10, -1)
 	})
 }
+
+func (s *decimalTestSuite) TestConvertToBigIntMutativeForLegacyDec() {
+	r := big.NewInt(30)
+	i := math.LegacyNewDecFromBigInt(r)
+
+	// Compare value of BigInt & BigIntMut
+	s.Require().Equal(i.BigInt(), i.BigIntMut())
+
+	// Modify BigIntMut() pointer and ensure i.BigIntMut() & i.BigInt() change
+	p1 := i.BigIntMut()
+	p1.SetInt64(40)
+	s.Require().Equal(big.NewInt(40), i.BigIntMut())
+	s.Require().Equal(big.NewInt(40), i.BigInt())
+
+	// Modify big.Int() pointer and ensure i.BigIntMut() & i.BigInt() don't change
+	p2 := i.BigInt()
+	p2.SetInt64(50)
+	s.Require().NotEqual(big.NewInt(50), i.BigIntMut())
+	s.Require().NotEqual(big.NewInt(50), i.BigInt())
+}