From 363b0c22c7a1c2a7d6f30bf7837bfe36cfbe1870 Mon Sep 17 00:00:00 2001
From: Mohamed Sameh <110535847+mohamedsamehsalah@users.noreply.github.com>
Date: Sat, 10 Aug 2024 16:49:44 +0200
Subject: [PATCH] Introduce `ArraysAsList` Refaster rule (#1275)

---
 .../refasterrules/CollectionRules.java        | 20 +++++++++++++++++++
 .../CollectionRulesTestInput.java             |  6 ++++++
 .../CollectionRulesTestOutput.java            |  6 ++++++
 3 files changed, 32 insertions(+)

diff --git a/error-prone-contrib/src/main/java/tech/picnic/errorprone/refasterrules/CollectionRules.java b/error-prone-contrib/src/main/java/tech/picnic/errorprone/refasterrules/CollectionRules.java
index ecbc7e51..4ee37189 100644
--- a/error-prone-contrib/src/main/java/tech/picnic/errorprone/refasterrules/CollectionRules.java
+++ b/error-prone-contrib/src/main/java/tech/picnic/errorprone/refasterrules/CollectionRules.java
@@ -8,7 +8,9 @@ import com.google.errorprone.refaster.Refaster;
 import com.google.errorprone.refaster.annotation.AfterTemplate;
 import com.google.errorprone.refaster.annotation.AlsoNegation;
 import com.google.errorprone.refaster.annotation.BeforeTemplate;
+import com.google.errorprone.refaster.annotation.NotMatches;
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.Collection;
 import java.util.Iterator;
 import java.util.List;
@@ -21,6 +23,7 @@ import java.util.function.Consumer;
 import java.util.function.IntFunction;
 import java.util.stream.Stream;
 import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
+import tech.picnic.errorprone.refaster.matchers.IsRefasterAsVarargs;
 
 /** Refaster rules related to expressions dealing with (arbitrary) collections. */
 // XXX: There are other Guava `Iterables` methods that should not be called if the input is known to
@@ -294,6 +297,23 @@ final class CollectionRules {
     }
   }
 
+  /** Prefer {@link Arrays#asList(Object[])} over more contrived alternatives. */
+  // XXX: Consider moving this rule to `ImmutableListRules` and having it suggest
+  // `ImmutableList#copyOf`. That would retain immutability, at the cost of no longer handling
+  // `null`s.
+  static final class ArraysAsList<T> {
+    // XXX: This expression produces an unmodifiable list, while the alternative doesn't.
+    @BeforeTemplate
+    List<T> before(@NotMatches(IsRefasterAsVarargs.class) T[] array) {
+      return Arrays.stream(array).toList();
+    }
+
+    @AfterTemplate
+    List<T> after(T[] array) {
+      return Arrays.asList(array);
+    }
+  }
+
   /** Prefer calling {@link Collection#toArray()} over more contrived alternatives. */
   static final class CollectionToArray<T> {
     @BeforeTemplate
diff --git a/error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/CollectionRulesTestInput.java b/error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/CollectionRulesTestInput.java
index 2968c3a0..c667a808 100644
--- a/error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/CollectionRulesTestInput.java
+++ b/error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/CollectionRulesTestInput.java
@@ -6,9 +6,11 @@ import com.google.common.collect.ImmutableSortedSet;
 import com.google.common.collect.Iterables;
 import com.google.common.collect.Lists;
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.HashSet;
 import java.util.Iterator;
 import java.util.LinkedList;
+import java.util.List;
 import java.util.Optional;
 import java.util.TreeSet;
 import java.util.stream.Stream;
@@ -98,6 +100,10 @@ final class CollectionRulesTest implements RefasterRuleCollectionTestCase {
     return ImmutableSet.of(1).asList().toString();
   }
 
+  List<String> testArraysAsList() {
+    return Arrays.stream(new String[0]).toList();
+  }
+
   ImmutableSet<Object[]> testCollectionToArray() {
     return ImmutableSet.of(
         ImmutableSet.of(1).toArray(new Object[1]),
diff --git a/error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/CollectionRulesTestOutput.java b/error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/CollectionRulesTestOutput.java
index 1eb0abc0..756135c8 100644
--- a/error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/CollectionRulesTestOutput.java
+++ b/error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/CollectionRulesTestOutput.java
@@ -6,9 +6,11 @@ import com.google.common.collect.ImmutableSortedSet;
 import com.google.common.collect.Iterables;
 import com.google.common.collect.Lists;
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.HashSet;
 import java.util.Iterator;
 import java.util.LinkedList;
+import java.util.List;
 import java.util.Optional;
 import java.util.TreeSet;
 import java.util.stream.Stream;
@@ -90,6 +92,10 @@ final class CollectionRulesTest implements RefasterRuleCollectionTestCase {
     return ImmutableSet.of(1).toString();
   }
 
+  List<String> testArraysAsList() {
+    return Arrays.asList(new String[0]);
+  }
+
   ImmutableSet<Object[]> testCollectionToArray() {
     return ImmutableSet.of(
         ImmutableSet.of(1).toArray(), ImmutableSet.of(2).toArray(), ImmutableSet.of(3).toArray());