Wrote 2 test cases, modified writeAll function to stop inwanted file creation

Author: ankitkumarrain

io/shared/src/main/scala/fs2/io/file/Files.scala

@@ -530,13 +530,21 @@ object Files extends FilesCompanionPlatform with FilesLowPriority {
       })
 
     def writeAll(
-        path: Path,
-        flags: Flags
-    ): Pipe[F, Byte, Nothing] =
+                  path: Path,
+                  flags: Flags
+                ): Pipe[F, Byte, Nothing] =
       in =>
-        Stream
-          .resource(writeCursor(path, flags))
-          .flatMap(_.writeAll(in).void.stream)
+        in.pull.stepLeg.flatMap {
+          case None => Pull.done
+          case Some(leg) =>
+            Stream
+              .resource(writeCursor(path, flags))
+              .flatMap { cursor =>
+                cursor.writeAll(leg.stream.cons(leg.head)).void.stream
+              }
+              .pull
+              .echo
+        }.stream
 
     def writeCursor(
         path: Path,

io/shared/src/test/scala/fs2/io/file/FilesSuite.scala

@@ -113,8 +113,8 @@ class FilesSuite extends Fs2Suite with BaseFileSuite {
           val src = Stream("Hello", " world!").covary[IO].through(text.utf8.encode)
           src.through(Files[IO].writeAll(path)) ++
             src.through(Files[IO].writeAll(path, Flags.Append)) ++ Files[IO]
-              .readAll(path)
-              .through(text.utf8.decode)
+            .readAll(path)
+            .through(text.utf8.decode)
         }
         .compile
         .foldMonoid
@@ -165,9 +165,10 @@ class FilesSuite extends Fs2Suite with BaseFileSuite {
         }
         .compile
         .foldMonoid
-        .assertEquals("""|foo
-                         |bar
-                         |""".stripMargin)
+        .assertEquals(
+          """|foo
+             |bar
+             |""".stripMargin)
     }
 
     test("writeUtf8Lines - side effect") {
@@ -200,6 +201,32 @@ class FilesSuite extends Fs2Suite with BaseFileSuite {
         .foldMonoid
         .assertEquals("")
     }
+    test("empty stream does not create file") {
+      Files[IO].tempDirectory.use { dir =>
+        val path = dir / "should-not-exist.txt"
+        Stream.empty
+          .covary[IO]
+          .through(Files[IO].writeAll(path))
+          .compile
+          .drain
+          .flatMap(_ => Files[IO].exists(path))
+          .assertEquals(false)
+      }
+    }
+
+    test("error stream does not create file") {
+      Files[IO].tempDirectory.use { dir =>
+        val path = dir / "should-not-exist.txt"
+        Stream
+          .raiseError[IO](new RuntimeException("boom"))
+          .through(Files[IO].writeAll(path))
+          .compile
+          .drain
+          .attempt
+          .flatMap(_ => Files[IO].exists(path))
+          .assertEquals(false)
+      }
+    }
   }
 
   group("tail") {