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PicnicSupermarket · Jan 20, 2024 · 1c930ba · 1c930ba
1 parent 000d9cd
commit 1c930ba
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Showing 3 changed files with 10 additions and 3 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
@@ -1042,12 +1042,15 @@ Mono<S> after(Flux<T> flux, Mono<S> mono) {
   /** Prefer {@link Mono#singleOptional()} over more contrived alternatives. */
   // XXX: Consider creating a plugin that flags/discourages `Mono<Optional<T>>` method return
   // types, just as we discourage nullable `Boolean`s and `Optional`s.
+  // XXX: The `mono.transform(Mono::singleOptional)` replacement is a special case of a more general
+  // rule. Consider introducing an Error Prone check for this.
   static final class MonoSingleOptional<T> {
     @BeforeTemplate
     Mono<Optional<T>> before(Mono<T> mono) {
       return Refaster.anyOf(
           mono.flux().collect(toOptional()),
-          mono.map(Optional::of).defaultIfEmpty(Optional.empty()));
+          mono.map(Optional::of).defaultIfEmpty(Optional.empty()),
+          mono.transform(Mono::singleOptional));
     }
 
     @AfterTemplate

diff --git a/...ontrib/src/test/resources/tech/picnic/errorprone/refasterrules/ReactorRulesTestInput.java b/...ontrib/src/test/resources/tech/picnic/errorprone/refasterrules/ReactorRulesTestInput.java
@@ -374,7 +374,8 @@ ImmutableSet<Mono<?>> testFluxThenMono() {
   ImmutableSet<Mono<Optional<String>>> testMonoSingleOptional() {
     return ImmutableSet.of(
         Mono.just("foo").flux().collect(toOptional()),
-        Mono.just("bar").map(Optional::of).defaultIfEmpty(Optional.empty()));
+        Mono.just("bar").map(Optional::of).defaultIfEmpty(Optional.empty()),
+        Mono.just("baz").transform(Mono::singleOptional));
   }
 
   Mono<Number> testMonoCast() {

diff --git a/...ntrib/src/test/resources/tech/picnic/errorprone/refasterrules/ReactorRulesTestOutput.java b/...ntrib/src/test/resources/tech/picnic/errorprone/refasterrules/ReactorRulesTestOutput.java
@@ -367,7 +367,10 @@ ImmutableSet<Mono<?>> testFluxThenMono() {
   }
 
   ImmutableSet<Mono<Optional<String>>> testMonoSingleOptional() {
-    return ImmutableSet.of(Mono.just("foo").singleOptional(), Mono.just("bar").singleOptional());
+    return ImmutableSet.of(
+        Mono.just("foo").singleOptional(),
+        Mono.just("bar").singleOptional(),
+        Mono.just("baz").singleOptional());
   }
 
   Mono<Number> testMonoCast() {