From 57f388ae94b73c75314ba81587fbf73407ee86ce Mon Sep 17 00:00:00 2001
From: Kien Dang <mail@kien.ai>
Date: Fri, 28 Jul 2023 16:33:17 +0800
Subject: [PATCH 1/2] Add Stream.filterNot

---
 core/shared/src/main/scala/fs2/Chunk.scala    |  3 ++
 core/shared/src/main/scala/fs2/Stream.scala   |  4 +++
 .../scala/fs2/StreamCombinatorsSuite.scala    | 34 +++++++++++++++++++
 3 files changed, 41 insertions(+)

diff --git a/core/shared/src/main/scala/fs2/Chunk.scala b/core/shared/src/main/scala/fs2/Chunk.scala
index df74ffecd1..e48d1db308 100644
--- a/core/shared/src/main/scala/fs2/Chunk.scala
+++ b/core/shared/src/main/scala/fs2/Chunk.scala
@@ -120,6 +120,9 @@ abstract class Chunk[+O] extends Serializable with ChunkPlatform[O] with ChunkRu
     Chunk.array(b.result()).asInstanceOf[Chunk[O]]
   }
 
+  /** Returns a chunk that has only the elements that do not satisfy the supplied predicate. */
+  def filterNot(p: O => Boolean): Chunk[O] = filter(p.andThen(!_))
+
   /** Returns the first element for which the predicate returns true or `None` if no elements satisfy the predicate. */
   def find(p: O => Boolean): Option[O] =
     iterator.find(p)
diff --git a/core/shared/src/main/scala/fs2/Stream.scala b/core/shared/src/main/scala/fs2/Stream.scala
index 1ab0dc3091..5120b635f6 100644
--- a/core/shared/src/main/scala/fs2/Stream.scala
+++ b/core/shared/src/main/scala/fs2/Stream.scala
@@ -1082,6 +1082,10 @@ final class Stream[+F[_], +O] private[fs2] (private[fs2] val underlying: Pull[F,
     */
   def filter(p: O => Boolean): Stream[F, O] = mapChunks(_.filter(p))
 
+  /** Emits only inputs which do not match the supplied predicate.
+    */
+  def filterNot(p: O => Boolean): Stream[F, O] = mapChunks(_.filterNot(p))
+
   /** Like `filter`, but allows filtering based on an effect.
     *
     * Note: The result Stream will consist of chunks that are empty or 1-element-long.
diff --git a/core/shared/src/test/scala/fs2/StreamCombinatorsSuite.scala b/core/shared/src/test/scala/fs2/StreamCombinatorsSuite.scala
index 0019e25f26..680c494e3e 100644
--- a/core/shared/src/test/scala/fs2/StreamCombinatorsSuite.scala
+++ b/core/shared/src/test/scala/fs2/StreamCombinatorsSuite.scala
@@ -567,6 +567,40 @@ class StreamCombinatorsSuite extends Fs2Suite {
     }
   }
 
+  group("filterNot") {
+    property("1") {
+      forAll { (s: Stream[Pure, Int], n0: Int) =>
+        val n = (n0 % 20).abs + 1
+        val predicate = (i: Int) => i % n == 0
+        s.filterNot(predicate).assertEmits(s.toList.filterNot(predicate))
+      }
+    }
+
+    property("2") {
+      forAll { (s: Stream[Pure, Double]) =>
+        val predicate = (i: Double) => i - i.floor < 0.5
+        val s2 = s.mapChunks(c => Chunk.array(c.toArray))
+        assertEquals(s2.filterNot(predicate).toList, s2.toList.filterNot(predicate))
+      }
+    }
+
+    property("3") {
+      forAll { (s: Stream[Pure, Byte]) =>
+        val predicate = (b: Byte) => b < 0
+        val s2 = s.mapChunks(c => Chunk.array(c.toArray))
+        s2.filterNot(predicate).assertEmits(s2.toList.filterNot(predicate))
+      }
+    }
+
+    property("4") {
+      forAll { (s: Stream[Pure, Boolean]) =>
+        val predicate = (b: Boolean) => !b
+        val s2 = s.mapChunks(c => Chunk.array(c.toArray))
+        s2.filterNot(predicate).assertEmits(s2.toList.filterNot(predicate))
+      }
+    }
+  }
+
   property("find") {
     forAll { (s: Stream[Pure, Int], i: Int) =>
       val predicate = (item: Int) => item < i

From 03ad1e338bfb362e6703f854f9b3c061a0eb7c70 Mon Sep 17 00:00:00 2001
From: Kien Dang <kiend@pm.me>
Date: Sun, 30 Jul 2023 11:14:50 +0800
Subject: [PATCH 2/2] Update core/shared/src/main/scala/fs2/Chunk.scala

Co-authored-by: Sergey Torgashov <satorg@users.noreply.github.com>
---
 core/shared/src/main/scala/fs2/Chunk.scala | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/core/shared/src/main/scala/fs2/Chunk.scala b/core/shared/src/main/scala/fs2/Chunk.scala
index e48d1db308..9e65bee0cf 100644
--- a/core/shared/src/main/scala/fs2/Chunk.scala
+++ b/core/shared/src/main/scala/fs2/Chunk.scala
@@ -121,7 +121,7 @@ abstract class Chunk[+O] extends Serializable with ChunkPlatform[O] with ChunkRu
   }
 
   /** Returns a chunk that has only the elements that do not satisfy the supplied predicate. */
-  def filterNot(p: O => Boolean): Chunk[O] = filter(p.andThen(!_))
+  def filterNot(p: O => Boolean): Chunk[O] = filter(!p(_))
 
   /** Returns the first element for which the predicate returns true or `None` if no elements satisfy the predicate. */
   def find(p: O => Boolean): Option[O] =