From 710520ebe1c00138d1d84be6eaeef43577503f62 Mon Sep 17 00:00:00 2001
From: Bastien Diederichs <bastien.diederichs@teampicnic.com>
Date: Thu, 27 Oct 2022 13:54:48 +0200
Subject: [PATCH] Drop redundant `::isInstance` in `onErrorResume`

---
 .../errorprone/refasterrules/ReactorRules.java      | 13 +++++++++++++
 .../refasterrules/ReactorRulesTestInput.java        |  5 +++++
 .../refasterrules/ReactorRulesTestOutput.java       |  4 ++++
 3 files changed, 22 insertions(+)

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
index 5f2f44045e..a98ab8d2e9 100644
--- 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
@@ -676,6 +676,19 @@ Flux<T> after(Flux<T> flux) {
     }
   }
 
+  /** Drop redundant {@link Class#isInstance} in {@link Mono#onErrorResume(Function)}. */
+  static final class MonoOnErrorResume<T> {
+    @BeforeTemplate
+    Mono<T> before(Mono<T> mono, Class<? extends Throwable> clazz, Mono<T> other) {
+      return mono.onErrorResume(clazz::isInstance, e -> other);
+    }
+
+    @AfterTemplate
+    Mono<T> after(Mono<T> mono, Class<? extends Throwable> clazz, Mono<T> other) {
+      return mono.onErrorResume(clazz, e -> other);
+    }
+  }
+
   /** Prefer {@link reactor.util.context.Context#empty()}} over more verbose alternatives. */
   // XXX: Consider introducing an `IsEmpty` matcher that identifies a wide range of guaranteed-empty
   // `Collection` and `Map` expressions.
diff --git a/error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/ReactorRulesTestInput.java b/error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/ReactorRulesTestInput.java
index 8c33d36b80..0e7519921e 100644
--- a/error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/ReactorRulesTestInput.java
+++ b/error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/ReactorRulesTestInput.java
@@ -218,6 +218,11 @@ ImmutableSet<Flux<Integer>> testFluxOnErrorComplete() {
         Flux.just(2).onErrorResume(e -> Flux.empty()));
   }
 
+  Mono<Integer> testMonoOnErrorResume() {
+    return Mono.just(1)
+        .onErrorResume(IllegalArgumentException.class::isInstance, e -> Mono.just(2));
+  }
+
   ImmutableSet<Context> testContextEmpty() {
     return ImmutableSet.of(Context.of(new HashMap<>()), Context.of(ImmutableMap.of()));
   }
diff --git a/error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/ReactorRulesTestOutput.java b/error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/ReactorRulesTestOutput.java
index b943f50ea4..795db5fcb4 100644
--- a/error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/ReactorRulesTestOutput.java
+++ b/error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/ReactorRulesTestOutput.java
@@ -218,6 +218,10 @@ ImmutableSet<Flux<Integer>> testFluxOnErrorComplete() {
     return ImmutableSet.of(Flux.just(1).onErrorComplete(), Flux.just(2).onErrorComplete());
   }
 
+  Mono<Integer> testMonoOnErrorResume() {
+    return Mono.just(1).onErrorResume(IllegalArgumentException.class, e -> Mono.just(2));
+  }
+
   ImmutableSet<Context> testContextEmpty() {
     return ImmutableSet.of(Context.empty(), Context.empty());
   }