Introduce {Max,Min}ByNaturalOrder Refaster rules (#970)

PicnicSupermarket · Jan 16, 2024 · 51317fb · 51317fb
1 parent e484926
commit 51317fb
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diff --git a/error-prone-contrib/src/main/java/tech/picnic/errorprone/refasterrules/ComparatorRules.java b/error-prone-contrib/src/main/java/tech/picnic/errorprone/refasterrules/ComparatorRules.java
@@ -7,6 +7,8 @@
 import static java.util.Comparator.comparingLong;
 import static java.util.Comparator.naturalOrder;
 import static java.util.Comparator.reverseOrder;
+import static java.util.stream.Collectors.maxBy;
+import static java.util.stream.Collectors.minBy;
 
 import com.google.common.collect.Comparators;
 import com.google.common.collect.ImmutableList;
@@ -21,11 +23,13 @@
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.Comparator;
+import java.util.Optional;
 import java.util.function.BinaryOperator;
 import java.util.function.Function;
 import java.util.function.ToDoubleFunction;
 import java.util.function.ToIntFunction;
 import java.util.function.ToLongFunction;
+import java.util.stream.Collector;
 import java.util.stream.Stream;
 import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
 import tech.picnic.errorprone.refaster.matchers.IsIdentityOperation;
@@ -383,4 +387,36 @@ BinaryOperator<T> after() {
       return Comparators::max;
     }
   }
+
+  /**
+   * Prefer {@link Comparator#naturalOrder()} over {@link Comparator#reverseOrder()} where possible.
+   */
+  static final class MinByNaturalOrder<T extends Comparable<? super T>> {
+    @BeforeTemplate
+    Collector<T, ?, Optional<T>> before() {
+      return maxBy(reverseOrder());
+    }
+
+    @AfterTemplate
+    @UseImportPolicy(STATIC_IMPORT_ALWAYS)
+    Collector<T, ?, Optional<T>> after() {
+      return minBy(naturalOrder());
+    }
+  }
+
+  /**
+   * Prefer {@link Comparator#naturalOrder()} over {@link Comparator#reverseOrder()} where possible.
+   */
+  static final class MaxByNaturalOrder<T extends Comparable<? super T>> {
+    @BeforeTemplate
+    Collector<T, ?, Optional<T>> before() {
+      return minBy(reverseOrder());
+    }
+
+    @AfterTemplate
+    @UseImportPolicy(STATIC_IMPORT_ALWAYS)
+    Collector<T, ?, Optional<T>> after() {
+      return maxBy(naturalOrder());
+    }
+  }
 }
diff --git a/...rib/src/test/resources/tech/picnic/errorprone/refasterrules/ComparatorRulesTestInput.java b/...rib/src/test/resources/tech/picnic/errorprone/refasterrules/ComparatorRulesTestInput.java
@@ -3,14 +3,18 @@
 import static java.util.Comparator.naturalOrder;
 import static java.util.Comparator.reverseOrder;
 import static java.util.function.Function.identity;
+import static java.util.stream.Collectors.maxBy;
+import static java.util.stream.Collectors.minBy;
 
 import com.google.common.collect.Comparators;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableSet;
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.Comparator;
+import java.util.Optional;
 import java.util.function.BinaryOperator;
+import java.util.stream.Collector;
 import java.util.stream.Stream;
 import tech.picnic.errorprone.refaster.test.RefasterRuleCollectionTestCase;
 
@@ -161,4 +165,12 @@ BinaryOperator<String> testComparatorsMin() {
   BinaryOperator<String> testComparatorsMax() {
     return BinaryOperator.maxBy(naturalOrder());
   }
+
+  Collector<Integer, ?, Optional<Integer>> testMinByNaturalOrder() {
+    return maxBy(reverseOrder());
+  }
+
+  Collector<Integer, ?, Optional<Integer>> testMaxByNaturalOrder() {
+    return minBy(reverseOrder());
+  }
 }
diff --git a/...ib/src/test/resources/tech/picnic/errorprone/refasterrules/ComparatorRulesTestOutput.java b/...ib/src/test/resources/tech/picnic/errorprone/refasterrules/ComparatorRulesTestOutput.java
@@ -3,14 +3,18 @@
 import static java.util.Comparator.naturalOrder;
 import static java.util.Comparator.reverseOrder;
 import static java.util.function.Function.identity;
+import static java.util.stream.Collectors.maxBy;
+import static java.util.stream.Collectors.minBy;
 
 import com.google.common.collect.Comparators;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableSet;
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.Comparator;
+import java.util.Optional;
 import java.util.function.BinaryOperator;
+import java.util.stream.Collector;
 import java.util.stream.Stream;
 import tech.picnic.errorprone.refaster.test.RefasterRuleCollectionTestCase;
 
@@ -151,4 +155,12 @@ BinaryOperator<String> testComparatorsMin() {
   BinaryOperator<String> testComparatorsMax() {
     return Comparators::max;
   }
+
+  Collector<Integer, ?, Optional<Integer>> testMinByNaturalOrder() {
+    return minBy(naturalOrder());
+  }
+
+  Collector<Integer, ?, Optional<Integer>> testMaxByNaturalOrder() {
+    return maxBy(naturalOrder());
+  }
 }