Introduce Reactor identity Refaster rules

PicnicSupermarket · Nov 28, 2022 · 5dacf5f · 5dacf5f
1 parent 6d15cfe
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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
@@ -639,6 +639,58 @@ Flux<S> after(Flux<T> flux) {
     }
   }
 
+  /** Prefer {@link Mono#flatMap(Function)} over more contrived alternatives. */
+  static final class MonoFlatMapIdentity<S, T> {
+    @BeforeTemplate
+    Mono<T> before(Mono<S> mono, Function<S, Mono<T>> function) {
+      return mono.map(function).flatMap(identity());
+    }
+
+    @AfterTemplate
+    Mono<T> after(Mono<S> mono, Function<S, Mono<T>> function) {
+      return mono.flatMap(function);
+    }
+  }
+
+  /** Prefer {@link Mono#flatMapMany(Function)} over more contrived alternatives. */
+  static final class FlatMapManyIdentity<S, T> {
+    @BeforeTemplate
+    Flux<T> before(Mono<S> mono, Function<S, ? extends Publisher<T>> function) {
+      return mono.map(function).flatMapMany(identity());
+    }
+
+    @AfterTemplate
+    Flux<T> after(Mono<S> mono, Function<S, ? extends Publisher<T>> function) {
+      return mono.flatMapMany(function);
+    }
+  }
+
+  /** Prefer {@link Flux#concatMap(Function)} over more contrived alternatives. */
+  static final class ConcatMapIdentity<S, T> {
+    @BeforeTemplate
+    Flux<T> before(Flux<S> flux, Function<S, ? extends Publisher<T>> function) {
+      return flux.map(function).concatMap(identity());
+    }
+
+    @AfterTemplate
+    Flux<T> after(Flux<S> flux, Function<S, ? extends Publisher<T>> function) {
+      return flux.concatMap(function);
+    }
+  }
+
+  /** Prefer {@link Flux#concatMap(Function, int)} over more contrived alternatives. */
+  static final class ConcatMapIdentityWithPrefetch<S, T> {
+    @BeforeTemplate
+    Flux<T> before(Flux<S> flux, Function<S, ? extends Publisher<T>> function, int prefetch) {
+      return flux.map(function).concatMap(identity(), prefetch);
+    }
+
+    @AfterTemplate
+    Flux<T> after(Flux<S> flux, Function<S, ? extends Publisher<T>> function, int prefetch) {
+      return flux.concatMap(function, prefetch);
+    }
+  }
+
   /**
    * 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;
@@ -207,6 +208,28 @@ Flux<Number> testFluxCast() {
     return Flux.just(1).map(Number.class::cast);
   }
 
+  Mono<String> testMonoFlatMapIdentity() {
+    return Mono.just("foo").map(Mono::just).flatMap(identity());
+  }
+
+  ImmutableSet<Flux<String>> testFlatMapManyIdentity() {
+    return ImmutableSet.of(
+        Mono.just("foo").map(Mono::just).flatMapMany(identity()),
+        Mono.just("foo").map(Flux::just).flatMapMany(identity()));
+  }
+
+  ImmutableSet<Flux<String>> testConcatMapIdentity() {
+    return ImmutableSet.of(
+        Flux.just("foo", "bar").map(Mono::just).concatMap(identity()),
+        Flux.just("foo", "bar").map(Flux::just).concatMap(identity()));
+  }
+
+  ImmutableSet<Flux<String>> testConcatMapIdentityWithPrefetch() {
+    return ImmutableSet.of(
+        Flux.just("foo", "bar").map(Mono::just).concatMap(identity(), 1),
+        Flux.just("foo", "bar").map(Flux::just).concatMap(identity(), 1));
+  }
+
   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
@@ -206,6 +206,27 @@ Flux<Number> testFluxCast() {
     return Flux.just(1).cast(Number.class);
   }
 
+  Mono<String> testMonoFlatMapIdentity() {
+    return Mono.just("foo").flatMap(Mono::just);
+  }
+
+  ImmutableSet<Flux<String>> testFlatMapManyIdentity() {
+    return ImmutableSet.of(
+        Mono.just("foo").flatMapMany(Mono::just), Mono.just("foo").flatMapMany(Flux::just));
+  }
+
+  ImmutableSet<Flux<String>> testConcatMapIdentity() {
+    return ImmutableSet.of(
+        Flux.just("foo", "bar").concatMap(Mono::just),
+        Flux.just("foo", "bar").concatMap(Flux::just));
+  }
+
+  ImmutableSet<Flux<String>> testConcatMapIdentityWithPrefetch() {
+    return ImmutableSet.of(
+        Flux.just("foo", "bar").concatMap(Mono::just, 1),
+        Flux.just("foo", "bar").concatMap(Flux::just, 1));
+  }
+
   ImmutableSet<Flux<String>> testConcatMapIterableIdentity() {
     return ImmutableSet.of(
         Flux.just(ImmutableList.of("foo")).concatMapIterable(identity()),