BasicSocket#recv* return `nil` rather than an empty packet

[Bug #19012]

man recvmsg(2) states:

> Return Value
> These calls return the number of bytes received, or -1 if an error occurred.
> The return value will be 0 when the peer has performed an orderly shutdown.

Not too sure how one is supposed to make the difference between a packet of
size 0 and a closed connection.

1 files changed, 66 insertions, 2 deletions

diff --git a/test/socket/test_unix.rb b/test/socket/test_unix.rb
index e206339db0..9d9faa4387 100644
--- a/test/socket/test_unix.rb
+++ b/test/socket/test_unix.rb
@@ -420,9 +420,10 @@ class TestSocket_UNIXSocket < Test::Unit::TestCase
       s1.recv_nonblock(10)
       fail
     rescue => e
-      assert(IO::EAGAINWaitReadable === e)
-      assert(IO::WaitReadable === e)
+      assert_kind_of(IO::EWOULDBLOCKWaitReadable, e)
+      assert_kind_of(IO::WaitReadable, e)
     end
+
     s2.send("", 0)
     s2.send("haha", 0)
     s2.send("", 0)
@@ -446,6 +447,69 @@ class TestSocket_UNIXSocket < Test::Unit::TestCase
     s2.close if s2
   end
 
+  def test_stream_pair
+    s1, s2 = UNIXSocket.pair(Socket::SOCK_STREAM)
+    begin
+      s1.recv_nonblock(10)
+      fail
+    rescue => e
+      assert_kind_of(IO::EWOULDBLOCKWaitReadable, e)
+      assert_kind_of(IO::WaitReadable, e)
+    end
+
+    s2.send("", 0)
+    s2.send("haha", 0)
+    assert_equal("haha", s1.recv(10))
+    assert_raise(IO::EWOULDBLOCKWaitReadable) { s1.recv_nonblock(10) }
+
+    buf = "".dup
+    s2.send("BBBBBB", 0)
+    IO.select([s1])
+    rv = s1.recv(100, 0, buf)
+    assert_equal buf.object_id, rv.object_id
+    assert_equal "BBBBBB", rv
+
+    s2.close
+    assert_nil(s1.recv(10))
+  rescue Errno::EPROTOTYPE => error
+    omit error.message
+  ensure
+    s1.close if s1
+    s2.close if s2
+  end
+
+  def test_seqpacket_pair
+    s1, s2 = UNIXSocket.pair(Socket::SOCK_SEQPACKET)
+    begin
+      s1.recv_nonblock(10)
+      fail
+    rescue => e
+      assert_kind_of(IO::EWOULDBLOCKWaitReadable, e)
+      assert_kind_of(IO::WaitReadable, e)
+    end
+
+    s2.send("", 0)
+    s2.send("haha", 0)
+    assert_equal(nil, s1.recv(10)) # no way to distinguish empty packet from EOF with SOCK_SEQPACKET
+    assert_equal("haha", s1.recv(10))
+    assert_raise(IO::EWOULDBLOCKWaitReadable) { s1.recv_nonblock(10) }
+
+    buf = "".dup
+    s2.send("BBBBBB", 0)
+    IO.select([s1])
+    rv = s1.recv(100, 0, buf)
+    assert_equal buf.object_id, rv.object_id
+    assert_equal "BBBBBB", rv
+
+    s2.close
+    assert_nil(s1.recv(10))
+  rescue Errno::EPROTOTYPE, Errno::EPROTONOSUPPORT => error
+    omit error.message
+  ensure
+    s1.close if s1
+    s2.close if s2
+  end
+
   def test_dgram_pair_sendrecvmsg_errno_set
     if /mswin|mingw/ =~ RUBY_PLATFORM
       omit("AF_UNIX + SOCK_DGRAM is not supported on windows")