From 866c5292a247b681dc250dd925ef05fa2b90bf50 Mon Sep 17 00:00:00 2001
From: Michael Pilquist <mpilquist@gmail.com>
Date: Sat, 4 Jan 2020 09:09:42 -0500
Subject: [PATCH 1/3] Added debug and debugChunks combinators

---
 core/shared/src/main/scala/fs2/Stream.scala | 63 +++++++++++++++++++++
 1 file changed, 63 insertions(+)

diff --git a/core/shared/src/main/scala/fs2/Stream.scala b/core/shared/src/main/scala/fs2/Stream.scala
index 9cece06549..6cfac632a1 100644
--- a/core/shared/src/main/scala/fs2/Stream.scala
+++ b/core/shared/src/main/scala/fs2/Stream.scala
@@ -656,6 +656,69 @@ final class Stream[+F[_], +O] private (private val free: FreeC[Nothing, O, Unit]
   def metered[F2[x] >: F[x]: Timer](rate: FiniteDuration): Stream[F2, O] =
     Stream.fixedRate[F2](rate).zipRight(this)
 
+  /**
+    * Logs the elements of this stream as they are pulled.
+    *
+    * If a tag is specified, it prefixes each element using the format `$tag: $o`.
+    * By default, log output is sent to standard out. Supply a different logger param
+    * to change this.
+    *
+    * This method does not change the chunk structure of the stream. To debug the
+    * chunk structure, see [[debugChunks]].
+    *
+    * Logging is not done in `F` because this operation is intended for debugging,
+    * including pure streams.
+    *
+    * @example {{{
+    * scala> Stream(1, 2).append(Stream(3, 4)).debug("a").toList
+    * a: 1
+    * a: 2
+    * a: 3
+    * a: 4
+    * res0: List[Int] = List(1, 2, 3, 4)
+    * }}}
+    */
+  def debug(tag: String = "", logger: String => Unit = println(_)): Stream[F, O] =
+    if (tag.isEmpty) debugFormat(_.toString, logger) else debugFormat(o => s"$tag: $o", logger)
+
+  /**
+    * Like [[debug]] but allows custom formatting of each element.
+    */
+  def debugFormat(formatter: O => String, logger: String => Unit = println(_)): Stream[F, O] =
+    map { o =>
+      logger(formatter(o))
+      o
+    }
+
+  /**
+    * Like [[debug]] but logs chunks as they are pulled instead of individual elements.
+    *
+    * @example {{{
+    * scala> Stream(1, 2, 3).append(Stream(4, 5, 6)).debugChunks("a").buffer(2).debugChunks("b").toList
+    * a: Chunk(1, 2, 3)
+    * b: Chunk(1, 2)
+    * a: Chunk(4, 5, 6)
+    * b: Chunk(3, 4)
+    * b: Chunk(5, 6)
+    * res0: List[Int] = List(1, 2, 3, 4, 5, 6)
+    * }}}
+    */
+  def debugChunks(tag: String = "", logger: String => Unit = println(_)): Stream[F, O] =
+    if (tag.isEmpty) debugChunksFormat(_.toString, logger)
+    else debugChunksFormat(o => s"$tag: $o", logger)
+
+  /**
+    * Like [[debugChunks]] but allows custom formatting of each chunk.
+    */
+  def debugChunksFormat(
+      formatter: Chunk[O] => String,
+      logger: String => Unit = println(_)
+  ): Stream[F, O] =
+    chunks.flatMap { os =>
+      logger(formatter(os))
+      Stream.chunk(os)
+    }
+
   /**
     * Returns a stream that when run, sleeps for duration `d` and then pulls from this stream.
     *

From 1e8c01026c572cb7b12bb15307aacf7a9c09acb5 Mon Sep 17 00:00:00 2001
From: Michael Pilquist <mpilquist@gmail.com>
Date: Tue, 7 Jan 2020 08:08:31 -0500
Subject: [PATCH 2/3] Combined debug/debugFormat and
 debugChunks/debugChunksFormat

---
 core/shared/src/main/scala/fs2/Stream.scala | 29 ++++++---------------
 1 file changed, 8 insertions(+), 21 deletions(-)

diff --git a/core/shared/src/main/scala/fs2/Stream.scala b/core/shared/src/main/scala/fs2/Stream.scala
index ac3ad19cd6..dbd9a86a64 100644
--- a/core/shared/src/main/scala/fs2/Stream.scala
+++ b/core/shared/src/main/scala/fs2/Stream.scala
@@ -659,9 +659,9 @@ final class Stream[+F[_], +O] private (private[fs2] val free: FreeC[F, O, Unit])
   /**
     * Logs the elements of this stream as they are pulled.
     *
-    * If a tag is specified, it prefixes each element using the format `$tag: $o`.
-    * By default, log output is sent to standard out. Supply a different logger param
-    * to change this.
+    * By default, `toString` is called on each element and the result is printed
+    * to standard out. To change formatting, supply a value for the `formatter`
+    * param. To change the destination, supply a value for the `logger` param.
     *
     * This method does not change the chunk structure of the stream. To debug the
     * chunk structure, see [[debugChunks]].
@@ -670,7 +670,7 @@ final class Stream[+F[_], +O] private (private[fs2] val free: FreeC[F, O, Unit])
     * including pure streams.
     *
     * @example {{{
-    * scala> Stream(1, 2).append(Stream(3, 4)).debug("a").toList
+    * scala> Stream(1, 2).append(Stream(3, 4)).debug(o => s"a: $o").toList
     * a: 1
     * a: 2
     * a: 3
@@ -678,13 +678,7 @@ final class Stream[+F[_], +O] private (private[fs2] val free: FreeC[F, O, Unit])
     * res0: List[Int] = List(1, 2, 3, 4)
     * }}}
     */
-  def debug(tag: String = "", logger: String => Unit = println(_)): Stream[F, O] =
-    if (tag.isEmpty) debugFormat(_.toString, logger) else debugFormat(o => s"$tag: $o", logger)
-
-  /**
-    * Like [[debug]] but allows custom formatting of each element.
-    */
-  def debugFormat(formatter: O => String, logger: String => Unit = println(_)): Stream[F, O] =
+  def debug(formatter: O => String = _.toString, logger: String => Unit = println(_)): Stream[F, O] =
     map { o =>
       logger(formatter(o))
       o
@@ -694,7 +688,7 @@ final class Stream[+F[_], +O] private (private[fs2] val free: FreeC[F, O, Unit])
     * Like [[debug]] but logs chunks as they are pulled instead of individual elements.
     *
     * @example {{{
-    * scala> Stream(1, 2, 3).append(Stream(4, 5, 6)).debugChunks("a").buffer(2).debugChunks("b").toList
+    * scala> Stream(1, 2, 3).append(Stream(4, 5, 6)).debugChunks(c => s"a: $c").buffer(2).debugChunks(c => s"b: $c").toList
     * a: Chunk(1, 2, 3)
     * b: Chunk(1, 2)
     * a: Chunk(4, 5, 6)
@@ -703,15 +697,8 @@ final class Stream[+F[_], +O] private (private[fs2] val free: FreeC[F, O, Unit])
     * res0: List[Int] = List(1, 2, 3, 4, 5, 6)
     * }}}
     */
-  def debugChunks(tag: String = "", logger: String => Unit = println(_)): Stream[F, O] =
-    if (tag.isEmpty) debugChunksFormat(_.toString, logger)
-    else debugChunksFormat(o => s"$tag: $o", logger)
-
-  /**
-    * Like [[debugChunks]] but allows custom formatting of each chunk.
-    */
-  def debugChunksFormat(
-      formatter: Chunk[O] => String,
+  def debugChunks(
+      formatter: Chunk[O] => String = _.toString,
       logger: String => Unit = println(_)
   ): Stream[F, O] =
     chunks.flatMap { os =>

From 403a348bc74d4a5b76665b1d2e3cee60f9c43347 Mon Sep 17 00:00:00 2001
From: Michael Pilquist <mpilquist@gmail.com>
Date: Tue, 7 Jan 2020 11:04:40 -0500
Subject: [PATCH 3/3] Scalafmt

---
 core/shared/src/main/scala/fs2/Stream.scala | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/core/shared/src/main/scala/fs2/Stream.scala b/core/shared/src/main/scala/fs2/Stream.scala
index dbd9a86a64..1068d4f0e6 100644
--- a/core/shared/src/main/scala/fs2/Stream.scala
+++ b/core/shared/src/main/scala/fs2/Stream.scala
@@ -678,7 +678,10 @@ final class Stream[+F[_], +O] private (private[fs2] val free: FreeC[F, O, Unit])
     * res0: List[Int] = List(1, 2, 3, 4)
     * }}}
     */
-  def debug(formatter: O => String = _.toString, logger: String => Unit = println(_)): Stream[F, O] =
+  def debug(
+      formatter: O => String = _.toString,
+      logger: String => Unit = println(_)
+  ): Stream[F, O] =
     map { o =>
       logger(formatter(o))
       o