From 7542d36993acb6ac6c219c30e6bbac3ab8d0b793 Mon Sep 17 00:00:00 2001
From: Kurt Alfred Kluever <kak@google.com>
Date: Mon, 26 Aug 2024 10:35:52 -0700
Subject: [PATCH] Don't fire `CanIgnoreReturnValueSuggester` for simple `return
 param;` implementations.

#checkreturnvalue

PiperOrigin-RevId: 667633531
---
 .../CanIgnoreReturnValueSuggester.java        | 10 ++++++
 .../CanIgnoreReturnValueSuggesterTest.java    | 34 +++++++++++++++++++
 2 files changed, 44 insertions(+)

diff --git a/core/src/main/java/com/google/errorprone/bugpatterns/checkreturnvalue/CanIgnoreReturnValueSuggester.java b/core/src/main/java/com/google/errorprone/bugpatterns/checkreturnvalue/CanIgnoreReturnValueSuggester.java
index 72d0a4ec697..7a7cf8836ba 100644
--- a/core/src/main/java/com/google/errorprone/bugpatterns/checkreturnvalue/CanIgnoreReturnValueSuggester.java
+++ b/core/src/main/java/com/google/errorprone/bugpatterns/checkreturnvalue/CanIgnoreReturnValueSuggester.java
@@ -153,6 +153,16 @@ public Description matchMethod(MethodTree methodTree, VisitorState state) {
 
     // if the method always return a single input param (of the same type), make it CIRV
     if (methodAlwaysReturnsInputParam(methodTree, state)) {
+      // if the method _only_ returns an input param, bail out
+      if (methodTree.getBody() != null && methodTree.getBody().getStatements().size() == 1) {
+        StatementTree onlyStatement = methodTree.getBody().getStatements().get(0);
+        if (onlyStatement instanceof ReturnTree) {
+          ReturnTree returnTree = (ReturnTree) onlyStatement;
+          if (returnTree.getExpression() instanceof IdentifierTree) {
+            return Description.NO_MATCH;
+          }
+        }
+      }
       return annotateWithCanIgnoreReturnValue(methodTree, state);
     }
 
diff --git a/core/src/test/java/com/google/errorprone/bugpatterns/checkreturnvalue/CanIgnoreReturnValueSuggesterTest.java b/core/src/test/java/com/google/errorprone/bugpatterns/checkreturnvalue/CanIgnoreReturnValueSuggesterTest.java
index a5f1606036d..a0b3349327f 100644
--- a/core/src/test/java/com/google/errorprone/bugpatterns/checkreturnvalue/CanIgnoreReturnValueSuggesterTest.java
+++ b/core/src/test/java/com/google/errorprone/bugpatterns/checkreturnvalue/CanIgnoreReturnValueSuggesterTest.java
@@ -56,6 +56,36 @@ public void simpleCase() {
         .doTest();
   }
 
+  @Test
+  public void b362106953_returnThis() {
+    helper
+        .addInputLines(
+            "Client.java",
+            "package com.google.frobber;",
+            "public final class Client {",
+            "  public Client setName(String name) {",
+            "    return this;",
+            "  }",
+            "}")
+        .expectUnchanged()
+        .doTest();
+  }
+
+  @Test
+  public void b362106953_returnParam() {
+    helper
+        .addInputLines(
+            "Client.java",
+            "package com.google.frobber;",
+            "public final class Client {",
+            "  public String setName(String name) {",
+            "    return name;",
+            "  }",
+            "}")
+        .expectUnchanged()
+        .doTest();
+  }
+
   @Test
   public void parenthesizedCastThis() {
     helper
@@ -92,6 +122,7 @@ public void returnsInputParam() {
             "package com.google.frobber;",
             "public final class Client {",
             "  public String method(String name) {",
+            "    System.out.println(name);",
             "    return name;",
             "  }",
             "}")
@@ -102,6 +133,7 @@ public void returnsInputParam() {
             "public final class Client {",
             "  @CanIgnoreReturnValue",
             "  public String method(String name) {",
+            "    System.out.println(name);",
             "    return name;",
             "  }",
             "}")
@@ -157,6 +189,7 @@ public void returnInputParams_multipleParams() {
             "package com.google.frobber;",
             "public final class ReturnInputParam {",
             "  public static StringBuilder append(StringBuilder input, String name) {",
+            "    input.append(name);",
             "    return input;",
             "  }",
             "}")
@@ -167,6 +200,7 @@ public void returnInputParams_multipleParams() {
             "public final class ReturnInputParam {",
             "  @CanIgnoreReturnValue",
             "  public static StringBuilder append(StringBuilder input, String name) {",
+            "    input.append(name);",
             "    return input;",
             "  }",
             "}")