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.

4 files changed, 32 insertions, 13 deletions

diff --git a/spec/ruby/library/socket/basicsocket/recv_spec.rb b/spec/ruby/library/socket/basicsocket/recv_spec.rb
index b6ccda5d00..a56114f4ab 100644
--- a/spec/ruby/library/socket/basicsocket/recv_spec.rb
+++ b/spec/ruby/library/socket/basicsocket/recv_spec.rb
@@ -32,6 +32,25 @@ describe "BasicSocket#recv" do
     ScratchPad.recorded.should == 'hello'
   end
 
+  ruby_version_is "3.3" do
+    it "returns nil on a closed stream socket" do
+      t = Thread.new do
+        client = @server.accept
+        packet = client.recv(10)
+        client.close
+        packet
+      end
+
+      Thread.pass while t.status and t.status != "sleep"
+      t.status.should_not be_nil
+
+      socket = TCPSocket.new('127.0.0.1', @port)
+      socket.close
+
+      t.value.should be_nil
+    end
+  end
+
   platform_is_not :solaris do
     it "accepts flags to specify unusual receiving behaviour" do
       t = Thread.new do
diff --git a/spec/ruby/library/socket/basicsocket/send_spec.rb b/spec/ruby/library/socket/basicsocket/send_spec.rb
index 868801df30..041ce03d72 100644
--- a/spec/ruby/library/socket/basicsocket/send_spec.rb
+++ b/spec/ruby/library/socket/basicsocket/send_spec.rb
@@ -22,7 +22,7 @@ describe "BasicSocket#send" do
        client = @server.accept
        loop do
          got = client.recv(5)
-         break if got.empty?
+         break if got.nil? || got.empty?
          data << got
        end
        client.close
@@ -67,7 +67,7 @@ describe "BasicSocket#send" do
        client = @server.accept
        loop do
          got = client.recv(5)
-         break if got.empty?
+         break if got.nil? || got.empty?
          data << got
        end
        client.close
diff --git a/spec/ruby/library/socket/basicsocket/shutdown_spec.rb b/spec/ruby/library/socket/basicsocket/shutdown_spec.rb
index 41d9581bde..c78b32de38 100644
--- a/spec/ruby/library/socket/basicsocket/shutdown_spec.rb
+++ b/spec/ruby/library/socket/basicsocket/shutdown_spec.rb
@@ -23,7 +23,7 @@ platform_is_not :windows do # hangs
         it 'shuts down a socket for reading' do
           @client.shutdown(Socket::SHUT_RD)
 
-          @client.recv(1).should be_empty
+          @client.recv(1).to_s.should be_empty
         end
 
         it 'shuts down a socket for writing' do
@@ -35,7 +35,7 @@ platform_is_not :windows do # hangs
         it 'shuts down a socket for reading and writing' do
           @client.shutdown(Socket::SHUT_RDWR)
 
-          @client.recv(1).should be_empty
+          @client.recv(1).to_s.should be_empty
 
           -> { @client.write('hello') }.should raise_error(Errno::EPIPE)
         end
@@ -49,13 +49,13 @@ platform_is_not :windows do # hangs
         it 'shuts down a socket for reading using :RD' do
           @client.shutdown(:RD)
 
-          @client.recv(1).should be_empty
+          @client.recv(1).to_s.should be_empty
         end
 
         it 'shuts down a socket for reading using :SHUT_RD' do
           @client.shutdown(:SHUT_RD)
 
-          @client.recv(1).should be_empty
+          @client.recv(1).to_s.should be_empty
         end
 
         it 'shuts down a socket for writing using :WR' do
@@ -73,7 +73,7 @@ platform_is_not :windows do # hangs
         it 'shuts down a socket for reading and writing' do
           @client.shutdown(:RDWR)
 
-          @client.recv(1).should be_empty
+          @client.recv(1).to_s.should be_empty
 
           -> { @client.write('hello') }.should raise_error(Errno::EPIPE)
         end
@@ -87,13 +87,13 @@ platform_is_not :windows do # hangs
         it 'shuts down a socket for reading using "RD"' do
           @client.shutdown('RD')
 
-          @client.recv(1).should be_empty
+          @client.recv(1).to_s.should be_empty
         end
 
         it 'shuts down a socket for reading using "SHUT_RD"' do
           @client.shutdown('SHUT_RD')
 
-          @client.recv(1).should be_empty
+          @client.recv(1).to_s.should be_empty
         end
 
         it 'shuts down a socket for writing using "WR"' do
@@ -123,7 +123,7 @@ platform_is_not :windows do # hangs
 
           @client.shutdown(@dummy)
 
-          @client.recv(1).should be_empty
+          @client.recv(1).to_s.should be_empty
         end
 
         it 'shuts down a socket for reading using "SHUT_RD"' do
@@ -131,7 +131,7 @@ platform_is_not :windows do # hangs
 
           @client.shutdown(@dummy)
 
-          @client.recv(1).should be_empty
+          @client.recv(1).to_s.should be_empty
         end
 
         it 'shuts down a socket for reading and writing' do
@@ -139,7 +139,7 @@ platform_is_not :windows do # hangs
 
           @client.shutdown(@dummy)
 
-          @client.recv(1).should be_empty
+          @client.recv(1).to_s.should be_empty
 
           -> { @client.write('hello') }.should raise_error(Errno::EPIPE)
         end
diff --git a/spec/ruby/library/socket/fixtures/classes.rb b/spec/ruby/library/socket/fixtures/classes.rb
index 406bd7c710..786629d2ef 100644
--- a/spec/ruby/library/socket/fixtures/classes.rb
+++ b/spec/ruby/library/socket/fixtures/classes.rb
@@ -113,7 +113,7 @@ module SocketSpecs
       begin
         data = socket.recv(1024)
 
-        return if data.empty?
+        return if data.nil? || data.empty?
         log "SpecTCPServer received: #{data.inspect}"
 
         return if data == "QUIT"