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Prefer flatMapIterable(identity()) over flatMap(i -> FluxfromIterable(i)) #279

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merged 4 commits into from
Oct 8, 2022
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Prefer flatMapIterable(identity()) over flatMap(i -> FluxfromIterable(i)) #279

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8650148
ANS-1289 Prefer `flatMapIterable(identity())` over `flatMap(i -> Flux…
Oct 5, 2022
0c414ea
ANS-1289 Extend to concatMap
Oct 5, 2022
651905b
Suggestions
Stephan202 Oct 6, 2022
0f7df62
Change generic from `S` to `T`
rickie Oct 7, 2022
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76 changes: 76 additions & 0 deletions ...rone-contrib/src/main/java/tech/picnic/errorprone/refastertemplates/ReactorTemplates.java
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Original file line number Diff line number Diff line change
Expand Up @@ -2,6 +2,7 @@

import static com.google.common.collect.MoreCollectors.toOptional;
import static com.google.errorprone.refaster.ImportPolicy.STATIC_IMPORT_ALWAYS;
import static java.util.function.Function.identity;
import static org.assertj.core.api.Assertions.assertThat;

import com.google.common.collect.MoreCollectors;
Expand Down Expand Up @@ -177,6 +178,26 @@ Flux<S> after(Flux<T> flux, Function<? super T, ? extends Publisher<? extends S>
}
}

/** Prefer {@link Flux#concatMap(Function, int)} over more contrived alternatives. */
static final class FluxConcatMapWithPrefetch<T, S> {
@BeforeTemplate
Flux<S> before(
Flux<T> flux,
Function<? super T, ? extends Publisher<? extends S>> function,
int prefetch) {
return Refaster.anyOf(
flux.flatMap(function, 1, prefetch), flux.flatMapSequential(function, 1, prefetch));
}

@AfterTemplate
Flux<S> after(
Flux<T> flux,
Function<? super T, ? extends Publisher<? extends S>> function,
int prefetch) {
return flux.concatMap(function, prefetch);
}
}

/**
* Prefer {@link Flux#concatMapIterable(Function)} over {@link Flux#flatMapIterable(Function)}, as
* the former has equivalent semantics but a clearer name.
Expand All @@ -193,6 +214,24 @@ Flux<S> after(Flux<T> flux, Function<? super T, ? extends Iterable<? extends S>>
}
}

/**
* Prefer {@link Flux#concatMapIterable(Function, int)} over {@link Flux#flatMapIterable(Function,
* int)}, as the former has equivalent semantics but a clearer name.
*/
static final class FluxConcatMapIterableWithPrefetch<T, S> {
@BeforeTemplate
Flux<S> before(
Flux<T> flux, Function<? super T, ? extends Iterable<? extends S>> function, int prefetch) {
return flux.flatMapIterable(function, prefetch);
}

@AfterTemplate
Flux<S> after(
Flux<T> flux, Function<? super T, ? extends Iterable<? extends S>> function, int prefetch) {
return flux.concatMapIterable(function, prefetch);
}
}

/**
* Don't use {@link Mono#flatMapMany(Function)} to implicitly convert a {@link Mono} to a {@link
* Flux}.
Expand Down Expand Up @@ -271,6 +310,43 @@ Flux<S> after(Flux<T> flux) {
}
}

/**
* Prefer {@link Flux#concatMapIterable(Function)} over alternatives that require an additional
* subscription.
*/
static final class ConcatMapIterableIdentity<S> {
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We use S when we need two generics, in this case we can simply use <T>.

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Ah yes :). (Also something to auto-unify on day 🙈.)

@BeforeTemplate
Flux<S> before(Flux<? extends Iterable<S>> flux) {
return Refaster.anyOf(
flux.concatMap(list -> Flux.fromIterable(list)), flux.concatMap(Flux::fromIterable));
}

@AfterTemplate
@UseImportPolicy(STATIC_IMPORT_ALWAYS)
Flux<S> after(Flux<? extends Iterable<S>> flux) {
return flux.concatMapIterable(identity());
}
}

/**
* Prefer {@link Flux#concatMapIterable(Function, int)} over alternatives that require an
* additional subscription.
*/
static final class ConcatMapIterableIdentityWithPrefetch<S> {
@BeforeTemplate
Flux<S> before(Flux<? extends Iterable<S>> flux, int prefetch) {
return Refaster.anyOf(
flux.concatMap(list -> Flux.fromIterable(list), prefetch),
flux.concatMap(Flux::fromIterable, prefetch));
}

@AfterTemplate
@UseImportPolicy(STATIC_IMPORT_ALWAYS)
Flux<S> after(Flux<? extends Iterable<S>> flux, int prefetch) {
return flux.concatMapIterable(identity(), prefetch);
}
}

/** Prefer {@link Mono#onErrorComplete()} over more contrived alternatives. */
static final class MonoOnErrorComplete<T> {
@BeforeTemplate
Expand Down
21 changes: 21 additions & 0 deletions ...rc/test/resources/tech/picnic/errorprone/refastertemplates/ReactorTemplatesTestInput.java
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Original file line number Diff line number Diff line change
Expand Up @@ -69,10 +69,19 @@ ImmutableSet<Flux<Integer>> testFluxConcatMap() {
Flux.just(1).flatMap(Mono::just, 1), Flux.just(2).flatMapSequential(Mono::just, 1));
}

ImmutableSet<Flux<Integer>> testFluxConcatMapWithPrefetch() {
return ImmutableSet.of(
Flux.just(1).flatMap(Mono::just, 1, 3), Flux.just(2).flatMapSequential(Mono::just, 1, 4));
}

Flux<Integer> testFluxConcatMapIterable() {
return Flux.just(1, 2).flatMapIterable(ImmutableList::of);
}

Flux<Integer> testFluxConcatMapIterableWithPrefetch() {
return Flux.just(1, 2).flatMapIterable(ImmutableList::of, 3);
}

Flux<String> testMonoFlatMapToFlux() {
return Mono.just("foo").flatMapMany(s -> Mono.just(s + s));
}
Expand All @@ -95,6 +104,18 @@ Flux<Number> testFluxCast() {
return Flux.just(1).map(Number.class::cast);
}

ImmutableSet<Flux<String>> testConcatMapIterableIdentity() {
return ImmutableSet.of(
Flux.just(ImmutableList.of("foo")).concatMap(list -> Flux.fromIterable(list)),
Flux.just(ImmutableList.of("bar")).concatMap(Flux::fromIterable));
}

ImmutableSet<Flux<String>> testConcatMapIterableIdentityWithPrefetch() {
return ImmutableSet.of(
Flux.just(ImmutableList.of("foo")).concatMap(list -> Flux.fromIterable(list), 1),
Flux.just(ImmutableList.of("bar")).concatMap(Flux::fromIterable, 2));
}

Mono<Integer> testMonoOnErrorComplete() {
return Mono.just(1).onErrorResume(e -> Mono.empty());
}
Expand Down
22 changes: 22 additions & 0 deletions ...c/test/resources/tech/picnic/errorprone/refastertemplates/ReactorTemplatesTestOutput.java
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Original file line number Diff line number Diff line change
@@ -1,6 +1,7 @@
package tech.picnic.errorprone.refastertemplates;

import static com.google.common.collect.MoreCollectors.toOptional;
import static java.util.function.Function.identity;
import static org.assertj.core.api.Assertions.assertThat;

import com.google.common.collect.ImmutableList;
Expand Down Expand Up @@ -68,10 +69,19 @@ ImmutableSet<Flux<Integer>> testFluxConcatMap() {
return ImmutableSet.of(Flux.just(1).concatMap(Mono::just), Flux.just(2).concatMap(Mono::just));
}

ImmutableSet<Flux<Integer>> testFluxConcatMapWithPrefetch() {
return ImmutableSet.of(
Flux.just(1).concatMap(Mono::just, 3), Flux.just(2).concatMap(Mono::just, 4));
}

Flux<Integer> testFluxConcatMapIterable() {
return Flux.just(1, 2).concatMapIterable(ImmutableList::of);
}

Flux<Integer> testFluxConcatMapIterableWithPrefetch() {
return Flux.just(1, 2).concatMapIterable(ImmutableList::of, 3);
}

Flux<String> testMonoFlatMapToFlux() {
return Mono.just("foo").flatMap(s -> Mono.just(s + s)).flux();
}
Expand All @@ -94,6 +104,18 @@ Flux<Number> testFluxCast() {
return Flux.just(1).cast(Number.class);
}

ImmutableSet<Flux<String>> testConcatMapIterableIdentity() {
return ImmutableSet.of(
Flux.just(ImmutableList.of("foo")).concatMapIterable(identity()),
Flux.just(ImmutableList.of("bar")).concatMapIterable(identity()));
}

ImmutableSet<Flux<String>> testConcatMapIterableIdentityWithPrefetch() {
return ImmutableSet.of(
Flux.just(ImmutableList.of("foo")).concatMapIterable(identity(), 1),
Flux.just(ImmutableList.of("bar")).concatMapIterable(identity(), 2));
}

Mono<Integer> testMonoOnErrorComplete() {
return Mono.just(1).onErrorComplete();
}
Expand Down