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MathFlux sum/average retains BigDecimal scale (#261)
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This commit ensures that no lossy conversion is made on a Number that
happens to be a BigDecimal already.

Furthermore, it uses the `new BigDecimal(String)` constructor instead
of `valueOf`, since creating BigDecimal from doubles can sometimes
result in less meaningful values due to double's limited precision.

Fixes #260.
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@kiwisincebirth
kiwisincebirth committed Sep 7, 2021
1 parent 4080569 commit a899661
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Showing 3 changed files with 41 additions and 27 deletions.
3 changes: 2 additions & 1 deletion reactor-extra/src/main/java/reactor/math/MonoAverageBigDecimal.java
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Original file line number Diff line number Diff line change
Expand Up @@ -75,7 +75,8 @@ protected BigDecimal result() {
@Override
protected void updateResult(T newValue) {
Number number = mapping.apply(newValue);
BigDecimal bigDecimalValue = BigDecimal.valueOf(number.doubleValue());
BigDecimal bigDecimalValue = (number instanceof BigDecimal) ?
(BigDecimal) number : new BigDecimal(number.toString());
sum = sum.add(bigDecimalValue);
count++;
}
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3 changes: 2 additions & 1 deletion reactor-extra/src/main/java/reactor/math/MonoSumBigDecimal.java
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Original file line number Diff line number Diff line change
Expand Up @@ -74,7 +74,8 @@ protected BigDecimal result() {
@Override
protected void updateResult(T newValue) {
Number number = mapping.apply(newValue);
BigDecimal bigDecimalValue = BigDecimal.valueOf(number.doubleValue());
BigDecimal bigDecimalValue = (number instanceof BigDecimal) ?
(BigDecimal) number : new BigDecimal(number.toString());
sum = hasValue ? sum.add(bigDecimalValue) : bigDecimalValue;
hasValue = true;
}
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62 changes: 37 additions & 25 deletions reactor-extra/src/test/java/reactor/math/ReactorMathTests.java
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Original file line number Diff line number Diff line change
Expand Up @@ -180,36 +180,49 @@ public void emptySumBigInteger() {
@Test
public void fluxSumBigDecimal() {
int count = 10;
BigDecimal sumDouble = BigDecimal.valueOf(Double.valueOf(sum(count)));
BigDecimal sum = BigDecimal.valueOf(sum(count));
verifyBigDecimalResult(MathFlux.sumBigDecimal(bigDecimalFlux(count)), sum);
verifyBigDecimalResult(MathFlux.sumBigDecimal(Flux.just(BigDecimal.valueOf(Double.MAX_VALUE),
verifyResult(MathFlux.sumBigDecimal(bigDecimalFlux(count)), sum);
verifyResult(MathFlux.sumBigDecimal(Flux.just(BigDecimal.valueOf(Double.MAX_VALUE),
BigDecimal.valueOf(Double.MAX_VALUE))),
BigDecimal.valueOf(Double.MAX_VALUE)
.multiply(BigDecimal.valueOf(2)));
verifyBigDecimalResult(MathFlux.sumBigDecimal(intFlux(count), i -> i), sum);
verifyBigDecimalResult(MathFlux.sumBigDecimal(doubleFlux(count), i -> i), sum);
verifyBigDecimalResult(MathFlux.sumBigDecimal(stringFlux(count), BigDecimal::new),
verifyResult(MathFlux.sumBigDecimal(intFlux(count), i -> i), sum);
verifyResult(MathFlux.sumBigDecimal(doubleFlux(count), i -> i), sumDouble);
verifyResult(MathFlux.sumBigDecimal(stringFlux(count), BigDecimal::new),
sum);

verifyBigDecimalResult(bigDecimalFlux(count).as(MathFlux::sumBigDecimal), sum);
verifyBigDecimalResult(bigDecimalFlux(count).transform(MathFlux::sumBigDecimal),
verifyResult(bigDecimalFlux(count).as(MathFlux::sumBigDecimal), sum);
verifyResult(bigDecimalFlux(count).transform(MathFlux::sumBigDecimal),
sum);
verifyBigDecimalResult(doubleFlux(count).as(MathFlux::sumBigDecimal), sum);
verifyBigDecimalResult(doubleFlux(count).transform(MathFlux::sumBigDecimal), sum);
verifyBigDecimalResult(intFlux(count).as(MathFlux::sumBigDecimal), sum);
verifyBigDecimalResult(intFlux(count).transform(MathFlux::sumBigDecimal), sum);
verifyResult(doubleFlux(count).as(MathFlux::sumBigDecimal), sumDouble);
verifyResult(doubleFlux(count).transform(MathFlux::sumBigDecimal), sumDouble);
verifyResult(intFlux(count).as(MathFlux::sumBigDecimal), sum);
verifyResult(intFlux(count).transform(MathFlux::sumBigDecimal), sum);
}

@Test
public void fluxSumBigDecimalWithPrecision() {
BigDecimal ONE = new BigDecimal("1.0000");
verifyResult(MathFlux.sumBigDecimal(Flux.just(ONE,ONE)),ONE.add(ONE));
}

@Test
public void monoSumBigDecimal() {
verifyBigDecimalResult(MathFlux.sumBigDecimal(Mono.just(BigDecimal.ONE)),
verifyResult(MathFlux.sumBigDecimal(Mono.just(BigDecimal.ONE)),
BigDecimal.ONE);
verifyBigDecimalResult(MathFlux.sumBigDecimal(Mono.just("10"), BigDecimal::new),
verifyResult(MathFlux.sumBigDecimal(Mono.just("10"), BigDecimal::new),
BigDecimal.TEN);
verifyBigDecimalResult(MathFlux.sumBigDecimal(Mono.just(1.5)),
verifyResult(MathFlux.sumBigDecimal(Mono.just(1.5)),
BigDecimal.valueOf(1.5D));
}

@Test
public void monoSumBigDecimalWithPrecision() {
BigDecimal ONE = new BigDecimal("1.0000");
verifyResult(MathFlux.sumBigDecimal(Mono.just(ONE)),ONE);
}

@Test
public void emptySumBigDecimal() {
verifyEmptyResult(MathFlux.sumBigDecimal(Mono.empty()));
Expand Down Expand Up @@ -308,34 +321,34 @@ public void emptyAverageBigInteger() {
public void fluxAverageBigDecimal() {
int count = 10;
BigDecimal average = BigDecimal.valueOf(average(count));
verifyBigDecimalResult(MathFlux.averageBigDecimal(bigDecimalFlux(count)),
verifyResult(MathFlux.averageBigDecimal(bigDecimalFlux(count)),
average);
verifyBigDecimalResult(MathFlux.averageBigDecimal(Flux.just(Double.MAX_VALUE,
Double.MAX_VALUE)),
BigDecimal.valueOf(Double.MAX_VALUE)
.multiply(BigDecimal.valueOf(2))
.divide(BigDecimal.valueOf(2)));
verifyBigDecimalResult(MathFlux.averageBigDecimal(intFlux(count), i -> i),
verifyResult(MathFlux.averageBigDecimal(intFlux(count), i -> i),
average);
verifyBigDecimalResult(MathFlux.averageBigDecimal(stringFlux(count),
verifyResult(MathFlux.averageBigDecimal(stringFlux(count),
Double::parseDouble), average);

verifyBigDecimalResult(doubleFlux(count).as(MathFlux::averageBigDecimal),
verifyResult(doubleFlux(count).as(MathFlux::averageBigDecimal),
average);
verifyBigDecimalResult(doubleFlux(count).transform(MathFlux::averageBigDecimal),
verifyResult(doubleFlux(count).transform(MathFlux::averageBigDecimal),
average);
verifyBigDecimalResult(intFlux(count).as(MathFlux::averageBigDecimal), average);
verifyBigDecimalResult(intFlux(count).transform(MathFlux::averageBigDecimal),
verifyResult(intFlux(count).as(MathFlux::averageBigDecimal), average);
verifyResult(intFlux(count).transform(MathFlux::averageBigDecimal),
average);
}

@Test
public void monoAverageBigDecimal() {
verifyBigDecimalResult(MathFlux.averageBigDecimal(Mono.just(2.5)),
verifyResult(MathFlux.averageBigDecimal(Mono.just(2.5)),
BigDecimal.valueOf(2.5));
verifyBigDecimalResult(MathFlux.averageBigDecimal(Mono.just(2), i -> i),
verifyResult(MathFlux.averageBigDecimal(Mono.just(2), i -> i),
BigDecimal.valueOf(2));
verifyBigDecimalResult(MathFlux.averageBigDecimal(Mono.just("1.5"),
verifyResult(MathFlux.averageBigDecimal(Mono.just("1.5"),
Double::parseDouble), BigDecimal.valueOf(1.5));
}

Expand Down Expand Up @@ -486,7 +499,6 @@ void verifyBigDecimalResult(Publisher<BigDecimal> resultMono,
BigDecimal expectedResult) {
StepVerifier.create(resultMono)
.expectNextMatches(t -> expectedResult.compareTo(t) == 0)
.expectNext()
.expectComplete()
.verify();
}
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