fix: Handle \r\n windows line endings.

internal/tailer/logstream/reader.go

@@ -72,12 +72,25 @@ func (lr *LineReader) send(ctx context.Context) bool {
 	if i < 0 {
 		return false
 	}
-	// TODO: Skip a previous \r
 	end := lr.off + i // excluding delim
+	skip := 1         // len of delim char
+
+	// Most file-based log sources will end with \n on Unixlike systems.  On
+	// Windows they appear to be both \r\n.  syslog disallows \r (and \t and
+	// others) and writes them escaped, per syslog(7).  [RFC
+	// 3164](https://www.ietf.org/rfc/rfc3164.txt) disallows newlines in the
+	// message: "The MSG part of the syslog packet MUST contain visible
+	// (printing) characters."  Thus if the previous char was a \r then ignore
+	// it as well.
+	if end > 0 && lr.buf[end-1] == '\r' {
+		end -= 1
+		skip = 2
+	}
+
 	line := string(lr.buf[lr.off:end])
 	logLines.Add(lr.sourcename, 1)
 	lr.lines <- logline.New(ctx, lr.sourcename, line)
-	lr.off = end + 1 // set past delim
+	lr.off = end + skip // move past delim
 	return true
 }
 

internal/tailer/logstream/reader_test.go

@@ -49,6 +49,11 @@ func TestReadAndSend(t *testing.T) {
 			input:   []byte("line 1\nline 2\n"),
 			wantOut: []string{"line 1", "line 2"},
 		},
+		{
+			name:    "windows line ending",
+			input:   []byte("line 1\r\nline \r2\n"),
+			wantOut: []string{"line 1", "line \r2"},
+		},
 	} {
 		t.Run(tc.name, func(t *testing.T) {
 			lines := make(chan *logline.LogLine, 5)