Introduce OptionalStream{Filter,Map} Refaster rules

PicnicSupermarket · Nov 2, 2022 · d4c6743 · d4c6743
1 parent be24eda
commit d4c6743
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diff --git a/error-prone-contrib/src/main/java/tech/picnic/errorprone/refasterrules/OptionalRules.java b/error-prone-contrib/src/main/java/tech/picnic/errorprone/refasterrules/OptionalRules.java
@@ -355,6 +355,41 @@ Optional<T> after(Optional<T> optional) {
     }
   }
 
+  /**
+   * Avoid unnecessary {@link Optional} to {@link Stream} conversion when filtering that ultimately
+   * returns the same result.
+   */
+  static final class OptionalStreamFilter<T> {
+    @BeforeTemplate
+    Optional<T> before(Optional<T> optional, Predicate<? super T> predicate) {
+      return Refaster.anyOf(
+          optional.stream().filter(predicate).findAny(),
+          optional.stream().filter(predicate).findFirst());
+    }
+
+    @AfterTemplate
+    Optional<T> after(Optional<T> optional, Predicate<? super T> predicate) {
+      return optional.filter(predicate);
+    }
+  }
+
+  /**
+   * Avoid unnecessary {@link Optional} to {@link Stream} conversion when mapping that ultimately
+   * returns the same result.
+   */
+  static final class OptionalStreamMap<S, T> {
+    @BeforeTemplate
+    Optional<? extends T> before(Optional<S> optional, Function<? super S, ? extends T> function) {
+      return Refaster.anyOf(
+          optional.stream().map(function).findAny(), optional.stream().map(function).findFirst());
+    }
+
+    @AfterTemplate
+    Optional<? extends T> after(Optional<S> optional, Function<? super S, ? extends T> function) {
+      return optional.map(function);
+    }
+  }
+
   // XXX: Add a rule for:
   // `optional.flatMap(x -> pred(x) ? Optional.empty() : Optional.of(x))` and variants.
   // (Maybe canonicalize the inner expression. Maybe we rewrite already.)

diff --git a/...ntrib/src/test/resources/tech/picnic/errorprone/refasterrules/OptionalRulesTestInput.java b/...ntrib/src/test/resources/tech/picnic/errorprone/refasterrules/OptionalRulesTestInput.java
@@ -109,4 +109,16 @@ ImmutableSet<Optional<String>> testOptionalIdentity() {
         Optional.of("baz").stream().min(String::compareTo),
         Optional.of("qux").stream().max(String::compareTo));
   }
+
+  ImmutableSet<Optional<String>> testOptionalStreamFilter() {
+    return ImmutableSet.of(
+        Optional.of("foo").stream().filter(String::isEmpty).findFirst(),
+        Optional.of("bar").stream().filter(String::isEmpty).findAny());
+  }
+
+  ImmutableSet<Optional<String>> testOptionalStreamMap() {
+    return ImmutableSet.of(
+        Optional.of(1).stream().map(String::valueOf).findFirst(),
+        Optional.of(2).stream().map(String::valueOf).findAny());
+  }
 }
diff --git a/...trib/src/test/resources/tech/picnic/errorprone/refasterrules/OptionalRulesTestOutput.java b/...trib/src/test/resources/tech/picnic/errorprone/refasterrules/OptionalRulesTestOutput.java
@@ -103,4 +103,14 @@ ImmutableSet<Optional<String>> testOptionalIdentity() {
     return ImmutableSet.of(
         Optional.of("foo"), Optional.of("bar"), Optional.of("baz"), Optional.of("qux"));
   }
+
+  ImmutableSet<Optional<String>> testOptionalStreamFilter() {
+    return ImmutableSet.of(
+        Optional.of("foo").filter(String::isEmpty), Optional.of("bar").filter(String::isEmpty));
+  }
+
+  ImmutableSet<Optional<String>> testOptionalStreamMap() {
+    return ImmutableSet.of(
+        Optional.of(1).map(String::valueOf), Optional.of(2).map(String::valueOf));
+  }
 }