Introduce StreamOf{1,2,3,4,5} Refaster rules (#814)

error-prone-contrib/src/main/java/tech/picnic/errorprone/refasterrules/StreamRules.java

@@ -20,6 +20,7 @@ import static java.util.stream.Collectors.summingDouble;
 import static java.util.stream.Collectors.summingInt;
 import static java.util.stream.Collectors.summingLong;
 
+import com.google.common.collect.ImmutableList;
 import com.google.common.collect.Streams;
 import com.google.errorprone.annotations.CanIgnoreReturnValue;
 import com.google.errorprone.refaster.Refaster;
@@ -668,4 +669,74 @@ final class StreamRules {
       return Stream.iterate(seed, hasNext, next);
     }
   }
+
+  /** Prefer {@link Stream#of(Object)} over more contrived alternatives. */
+  // XXX: Generalize this and similar rules using an Error Prone check.
+  static final class StreamOf1<T> {
+    @BeforeTemplate
+    Stream<T> before(T e1) {
+      return ImmutableList.of(e1).stream();
+    }
+
+    @AfterTemplate
+    Stream<T> after(T e1) {
+      return Stream.of(e1);
+    }
+  }
+
+  /** Prefer {@link Stream#of(Object[])} over more contrived alternatives. */
+  // XXX: Generalize this and similar rules using an Error Prone check.
+  static final class StreamOf2<T> {
+    @BeforeTemplate
+    Stream<T> before(T e1, T e2) {
+      return ImmutableList.of(e1, e2).stream();
+    }
+
+    @AfterTemplate
+    Stream<T> after(T e1, T e2) {
+      return Stream.of(e1, e2);
+    }
+  }
+
+  /** Prefer {@link Stream#of(Object[])} over more contrived alternatives. */
+  // XXX: Generalize this and similar rules using an Error Prone check.
+  static final class StreamOf3<T> {
+    @BeforeTemplate
+    Stream<T> before(T e1, T e2, T e3) {
+      return ImmutableList.of(e1, e2, e3).stream();
+    }
+
+    @AfterTemplate
+    Stream<T> after(T e1, T e2, T e3) {
+      return Stream.of(e1, e2, e3);
+    }
+  }
+
+  /** Prefer {@link Stream#of(Object[])} over more contrived alternatives. */
+  // XXX: Generalize this and similar rules using an Error Prone check.
+  static final class StreamOf4<T> {
+    @BeforeTemplate
+    Stream<T> before(T e1, T e2, T e3, T e4) {
+      return ImmutableList.of(e1, e2, e3, e4).stream();
+    }
+
+    @AfterTemplate
+    Stream<T> after(T e1, T e2, T e3, T e4) {
+      return Stream.of(e1, e2, e3, e4);
+    }
+  }
+
+  /** Prefer {@link Stream#of(Object[])} over more contrived alternatives. */
+  // XXX: Generalize this and similar rules using an Error Prone check.
+  static final class StreamOf5<T> {
+    @BeforeTemplate
+    Stream<T> before(T e1, T e2, T e3, T e4, T e5) {
+      return ImmutableList.of(e1, e2, e3, e4, e5).stream();
+    }
+
+    @AfterTemplate
+    Stream<T> after(T e1, T e2, T e3, T e4, T e5) {
+      return Stream.of(e1, e2, e3, e4, e5);
+    }
+  }
 }

error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/StreamRulesTestInput.java

@@ -20,6 +20,7 @@ import static java.util.stream.Collectors.summingDouble;
 import static java.util.stream.Collectors.summingInt;
 import static java.util.stream.Collectors.summingLong;
 
+import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableSet;
 import com.google.common.collect.Streams;
 import java.util.DoubleSummaryStatistics;
@@ -36,6 +37,7 @@ final class StreamRulesTest implements RefasterRuleCollectionTestCase {
   @Override
   public ImmutableSet<Object> elidedTypesAndStaticImports() {
     return ImmutableSet.of(
+        ImmutableList.class,
         Objects.class,
         Streams.class,
         counting(),
@@ -266,4 +268,24 @@ final class StreamRulesTest implements RefasterRuleCollectionTestCase {
   Stream<Integer> testStreamIterate() {
     return Stream.iterate(0, i -> i + 1).takeWhile(i -> i < 10);
   }
+
+  Stream<Integer> testStreamOf1() {
+    return ImmutableList.of(1).stream();
+  }
+
+  Stream<Integer> testStreamOf2() {
+    return ImmutableList.of(1, 2).stream();
+  }
+
+  Stream<Integer> testStreamOf3() {
+    return ImmutableList.of(1, 2, 3).stream();
+  }
+
+  Stream<Integer> testStreamOf4() {
+    return ImmutableList.of(1, 2, 3, 4).stream();
+  }
+
+  Stream<Integer> testStreamOf5() {
+    return ImmutableList.of(1, 2, 3, 4, 5).stream();
+  }
 }

error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/StreamRulesTestOutput.java

@@ -21,6 +21,7 @@ import static java.util.stream.Collectors.summingDouble;
 import static java.util.stream.Collectors.summingInt;
 import static java.util.stream.Collectors.summingLong;
 
+import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableSet;
 import com.google.common.collect.Streams;
 import java.util.Arrays;
@@ -38,6 +39,7 @@ final class StreamRulesTest implements RefasterRuleCollectionTestCase {
   @Override
   public ImmutableSet<Object> elidedTypesAndStaticImports() {
     return ImmutableSet.of(
+        ImmutableList.class,
         Objects.class,
         Streams.class,
         counting(),
@@ -266,4 +268,24 @@ final class StreamRulesTest implements RefasterRuleCollectionTestCase {
   Stream<Integer> testStreamIterate() {
     return Stream.iterate(0, i -> i < 10, i -> i + 1);
   }
+
+  Stream<Integer> testStreamOf1() {
+    return Stream.of(1);
+  }
+
+  Stream<Integer> testStreamOf2() {
+    return Stream.of(1, 2);
+  }
+
+  Stream<Integer> testStreamOf3() {
+    return Stream.of(1, 2, 3);
+  }
+
+  Stream<Integer> testStreamOf4() {
+    return Stream.of(1, 2, 3, 4);
+  }
+
+  Stream<Integer> testStreamOf5() {
+    return Stream.of(1, 2, 3, 4, 5);
+  }
 }