Add Refaster template for StepVerifier#create to use Fluent API

error-prone-contrib/src/main/java/tech/picnic/errorprone/refastertemplates/ReactorTemplates.java

@@ -220,6 +220,32 @@ PublisherProbe<T> after() {
     }
   }
 
+  /** Prefer {@link Mono#as(Function)} when creating a {@link StepVerifier}. */
+  static final class StepVerifierFromMono<T> {
+    @BeforeTemplate
+    StepVerifier.FirstStep<? extends T> before(Mono<T> mono) {
+      return StepVerifier.create(mono);
+    }
+
+    @AfterTemplate
+    StepVerifier.FirstStep<? extends T> after(Mono<T> mono) {
+      return mono.as(StepVerifier::create);
+    }
+  }
+
+  /** Prefer {@link Flux#as(Function)} when creating a {@link StepVerifier}. */
+  static final class StepVerifierFromFlux<T> {
+    @BeforeTemplate
+    StepVerifier.FirstStep<? extends T> before(Flux<T> flux) {
+      return StepVerifier.create(flux);
+    }
+
+    @AfterTemplate
+    StepVerifier.FirstStep<? extends T> after(Flux<T> flux) {
+      return flux.as(StepVerifier::create);
+    }
+  }
+
   /** Don't unnecessarily call {@link StepVerifier.Step#expectNext(Object[])}. */
   static final class StepVerifierStepExpectNextEmpty<T> {
     @BeforeTemplate

error-prone-contrib/src/test/resources/tech/picnic/errorprone/bugpatterns/ReactorTemplatesTestInput.java

@@ -67,6 +67,14 @@ ImmutableSet<PublisherProbe<Void>> testPublisherProbeEmpty() {
     return ImmutableSet.of(PublisherProbe.of(Mono.empty()), PublisherProbe.of(Flux.empty()));
   }
 
+  StepVerifier.FirstStep<Integer> testStepVerifierFromMono() {
+    return StepVerifier.create(Mono.just(1));
+  }
+
+  StepVerifier.FirstStep<Integer> testStepVerifierFromFlux() {
+    return StepVerifier.create(Flux.just(1));
+  }
+
   StepVerifier.Step<Integer> testStepVerifierStepExpectNextEmpty() {
     return StepVerifier.create(Mono.just(0)).expectNext();
   }

error-prone-contrib/src/test/resources/tech/picnic/errorprone/bugpatterns/ReactorTemplatesTestOutput.java

@@ -68,6 +68,14 @@ ImmutableSet<PublisherProbe<Void>> testPublisherProbeEmpty() {
     return ImmutableSet.of(PublisherProbe.empty(), PublisherProbe.empty());
   }
 
+  StepVerifier.FirstStep<Integer> testStepVerifierFromMono() {
+    return Mono.just(1).as(StepVerifier::create);
+  }
+
+  StepVerifier.FirstStep<Integer> testStepVerifierFromFlux() {
+    return Flux.just(1).as(StepVerifier::create);
+  }
+
   StepVerifier.Step<Integer> testStepVerifierStepExpectNextEmpty() {
     return StepVerifier.create(Mono.just(0));
   }