improve handling of newline characters of the command line

Author: smdn

src/Smdn.Net.MuninNode/Smdn.Net.MuninNode/NodeBase.cs

@@ -538,16 +538,27 @@ await RespondToCommandAsync(
     static bool TryReadLine(ref ReadOnlySequence<byte> buffer, out ReadOnlySequence<byte> line)
     {
       var reader = new SequenceReader<byte>(buffer);
+      const byte CR = (byte)'\r';
       const byte LF = (byte)'\n';
 
-      if (
-        !reader.TryReadTo(out line, delimiter: "\r\n"u8, advancePastDelimiter: true) &&
-        !reader.TryReadTo(out line, delimiter: LF, advancePastDelimiter: true)
-      ) {
+      // read sequence until LF
+      if (!reader.TryReadTo(out line, delimiter: LF, advancePastDelimiter: true)) {
         line = default;
         return false;
       }
 
+      // trim the CR just before the LF, in case the line ends with CRLF
+      var lineLength = line.Length;
+
+      if (0 < lineLength) {
+        var lineReader = new SequenceReader<byte>(line);
+
+        lineReader.Advance(lineLength - 1);
+
+        if (lineReader.UnreadSpan[0] == CR)
+          line = line.Slice(0, lineLength - 1);
+      }
+
 #if SYSTEM_BUFFERS_SEQUENCEREADER_UNREADSEQUENCE
       buffer = reader.UnreadSequence;
 #else

tests/Smdn.Net.MuninNode/Smdn.Net.MuninNode/NodeBase.Commands.cs

@@ -118,10 +118,14 @@ private static async Task RunSessionAsync(
     }
   }
 
-  [TestCase("\r\n")]
-  [TestCase("\n")]
+  [TestCase("\r\n", "# Unknown command.")]
+  [TestCase("\n", "# Unknown command.")]
+  [TestCase("foo\r\n", "# Unknown command.")]
+  [TestCase("foo\n", "# Unknown command.")]
+  [TestCase(".\r\n", null)]
+  [TestCase(".\n", null)]
   [CancelAfter(3000)]
-  public async Task ProcessCommandAsync_EndOfLine(string eol, CancellationToken cancellationToken)
+  public async Task ProcessCommandAsync_EndOfLine(string commandLine, string? expectedResponseLinePrefix, CancellationToken cancellationToken)
   {
     PseudoMuninNodeClient? acceptedClient = null;
 
@@ -131,9 +135,17 @@ await RunSessionAsync(
       async (node, client, writer, reader, ct) => {
         Assert.That(client.IsConnected, Is.True);
 
-        await writer.WriteAsync(("." + eol).AsMemory(), ct);
-
         acceptedClient = client;
+
+        await writer.WriteAsync(commandLine.AsMemory(), ct);
+        await writer.FlushAsync(ct);
+
+        Assert.That(
+          await reader.ReadLineAsync(ct),
+          expectedResponseLinePrefix is null
+            ? Is.Null
+            : Does.StartWith(expectedResponseLinePrefix)
+        );
       },
       cancellationToken: cancellationToken
     );