Introduce some Refaster rules that avoid nested Publishers (#374)

PicnicSupermarket · Nov 28, 2022 · f46859a · f46859a
1 parent 6d15cfe
commit f46859a
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Showing 3 changed files with 63 additions and 6 deletions.
diff --git a/error-prone-contrib/src/main/java/tech/picnic/errorprone/refasterrules/ReactorRules.java b/error-prone-contrib/src/main/java/tech/picnic/errorprone/refasterrules/ReactorRules.java
@@ -320,7 +320,10 @@ Flux<T> after(Flux<T> flux) {
   static final class FluxConcatMap<T, S> {
     @BeforeTemplate
     Flux<S> before(Flux<T> flux, Function<? super T, ? extends Publisher<? extends S>> function) {
-      return Refaster.anyOf(flux.flatMap(function, 1), flux.flatMapSequential(function, 1));
+      return Refaster.anyOf(
+          flux.flatMap(function, 1),
+          flux.flatMapSequential(function, 1),
+          flux.map(function).concatMap(identity()));
     }
 
     @AfterTemplate
@@ -337,7 +340,9 @@ Flux<S> before(
         Function<? super T, ? extends Publisher<? extends S>> function,
         int prefetch) {
       return Refaster.anyOf(
-          flux.flatMap(function, 1, prefetch), flux.flatMapSequential(function, 1, prefetch));
+          flux.flatMap(function, 1, prefetch),
+          flux.flatMapSequential(function, 1, prefetch),
+          flux.map(function).concatMap(identity(), prefetch));
     }
 
     @AfterTemplate
@@ -639,6 +644,32 @@ Flux<S> after(Flux<T> flux) {
     }
   }
 
+  /** Prefer {@link Mono#flatMap(Function)} over more contrived alternatives. */
+  static final class MonoFlatMap<S, T> {
+    @BeforeTemplate
+    Mono<T> before(Mono<S> mono, Function<? super S, ? extends Mono<? extends T>> function) {
+      return mono.map(function).flatMap(identity());
+    }
+
+    @AfterTemplate
+    Mono<T> after(Mono<S> mono, Function<? super S, ? extends Mono<? extends T>> function) {
+      return mono.flatMap(function);
+    }
+  }
+
+  /** Prefer {@link Mono#flatMapMany(Function)} over more contrived alternatives. */
+  static final class MonoFlatMapMany<S, T> {
+    @BeforeTemplate
+    Flux<T> before(Mono<S> mono, Function<? super S, ? extends Publisher<? extends T>> function) {
+      return mono.map(function).flatMapMany(identity());
+    }
+
+    @AfterTemplate
+    Flux<T> after(Mono<S> mono, Function<? super S, ? extends Publisher<? extends T>> function) {
+      return mono.flatMapMany(function);
+    }
+  }
+
   /**
    * Prefer {@link Flux#concatMapIterable(Function)} over alternatives that require an additional
    * subscription.

diff --git a/...ontrib/src/test/resources/tech/picnic/errorprone/refasterrules/ReactorRulesTestInput.java b/...ontrib/src/test/resources/tech/picnic/errorprone/refasterrules/ReactorRulesTestInput.java
@@ -1,5 +1,6 @@
 package tech.picnic.errorprone.refasterrules;
 
+import static java.util.function.Function.identity;
 import static org.assertj.core.api.Assertions.assertThat;
 
 import com.google.common.collect.ImmutableList;
@@ -104,12 +105,16 @@ ImmutableSet<Flux<Integer>> testFluxSwitchIfEmptyOfEmptyPublisher() {
 
   ImmutableSet<Flux<Integer>> testFluxConcatMap() {
     return ImmutableSet.of(
-        Flux.just(1).flatMap(Mono::just, 1), Flux.just(2).flatMapSequential(Mono::just, 1));
+        Flux.just(1).flatMap(Mono::just, 1),
+        Flux.just(2).flatMapSequential(Mono::just, 1),
+        Flux.just(3).map(Mono::just).concatMap(identity()));
   }
 
   ImmutableSet<Flux<Integer>> testFluxConcatMapWithPrefetch() {
     return ImmutableSet.of(
-        Flux.just(1).flatMap(Mono::just, 1, 3), Flux.just(2).flatMapSequential(Mono::just, 1, 4));
+        Flux.just(1).flatMap(Mono::just, 1, 3),
+        Flux.just(2).flatMapSequential(Mono::just, 1, 4),
+        Flux.just(3).map(Mono::just).concatMap(identity(), 5));
   }
 
   Flux<Integer> testFluxConcatMapIterable() {
@@ -207,6 +212,14 @@ Flux<Number> testFluxCast() {
     return Flux.just(1).map(Number.class::cast);
   }
 
+  Mono<String> testMonoFlatMap() {
+    return Mono.just("foo").map(Mono::just).flatMap(identity());
+  }
+
+  Flux<String> testMonoFlatMapMany() {
+    return Mono.just("foo").map(Mono::just).flatMapMany(identity());
+  }
+
   ImmutableSet<Flux<String>> testConcatMapIterableIdentity() {
     return ImmutableSet.of(
         Flux.just(ImmutableList.of("foo")).concatMap(list -> Flux.fromIterable(list)),

diff --git a/...ntrib/src/test/resources/tech/picnic/errorprone/refasterrules/ReactorRulesTestOutput.java b/...ntrib/src/test/resources/tech/picnic/errorprone/refasterrules/ReactorRulesTestOutput.java
@@ -108,12 +108,17 @@ ImmutableSet<Flux<Integer>> testFluxSwitchIfEmptyOfEmptyPublisher() {
   }
 
   ImmutableSet<Flux<Integer>> testFluxConcatMap() {
-    return ImmutableSet.of(Flux.just(1).concatMap(Mono::just), Flux.just(2).concatMap(Mono::just));
+    return ImmutableSet.of(
+        Flux.just(1).concatMap(Mono::just),
+        Flux.just(2).concatMap(Mono::just),
+        Flux.just(3).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.just(1).concatMap(Mono::just, 3),
+        Flux.just(2).concatMap(Mono::just, 4),
+        Flux.just(3).concatMap(Mono::just, 5));
   }
 
   Flux<Integer> testFluxConcatMapIterable() {
@@ -206,6 +211,14 @@ Flux<Number> testFluxCast() {
     return Flux.just(1).cast(Number.class);
   }
 
+  Mono<String> testMonoFlatMap() {
+    return Mono.just("foo").flatMap(Mono::just);
+  }
+
+  Flux<String> testMonoFlatMapMany() {
+    return Mono.just("foo").flatMapMany(Mono::just);
+  }
+
   ImmutableSet<Flux<String>> testConcatMapIterableIdentity() {
     return ImmutableSet.of(
         Flux.just(ImmutableList.of("foo")).concatMapIterable(identity()),