From 5c3f42aa4e086fbdb5976ece09adc0a1e9e6ba79 Mon Sep 17 00:00:00 2001
From: Vitaly Potyarkin <sio.wtf@gmail.com>
Date: Thu, 27 Apr 2023 14:00:42 +0000
Subject: [PATCH] Add tests to detect forever hanging Read()

---
 io_test.go | 102 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 102 insertions(+)
 create mode 100644 io_test.go

diff --git a/io_test.go b/io_test.go
new file mode 100644
index 0000000..f68956c
--- /dev/null
+++ b/io_test.go
@@ -0,0 +1,102 @@
+package pty
+
+import (
+	"testing"
+
+	"context"
+	"os"
+	"sync"
+	"time"
+)
+
+const (
+	errMarker byte = 0xEE
+	timeout        = time.Second
+)
+
+var mu sync.Mutex
+
+// Check that SetDeadline() works for ptmx.
+// Outstanding Read() calls must be interrupted by deadline.
+//
+// https://github.com/creack/pty/issues/162
+func TestReadDeadline(t *testing.T) {
+	ptmx, success := prepare(t)
+
+	err := ptmx.SetDeadline(time.Now().Add(timeout / 10))
+	if err != nil {
+		t.Fatalf("error: set deadline: %v\n", err)
+	}
+
+	var buf = make([]byte, 1)
+	n, err := ptmx.Read(buf)
+	success()
+
+	if n != 0 && buf[0] != errMarker {
+		t.Errorf("received unexpected data from pmtx (%d bytes): 0x%X; err=%v", n, buf, err)
+	}
+}
+
+// Check that ptmx.Close() interrupts outstanding ptmx.Read() calls
+//
+// https://github.com/creack/pty/issues/114
+// https://github.com/creack/pty/issues/88
+func TestReadClose(t *testing.T) {
+	ptmx, success := prepare(t)
+
+	go func() {
+		time.Sleep(timeout / 10)
+		err := ptmx.Close()
+		if err != nil {
+			t.Errorf("failed to close ptmx: %v", err)
+		}
+	}()
+
+	var buf = make([]byte, 1)
+	n, err := ptmx.Read(buf)
+	success()
+
+	if n != 0 && buf[0] != errMarker {
+		t.Errorf("received unexpected data from pmtx (%d bytes): 0x%X; err=%v", n, buf, err)
+	}
+}
+
+// Open pty and setup watchdogs for graceful and not so graceful failure modes
+func prepare(t *testing.T) (ptmx *os.File, done func()) {
+
+	// Due to data race potential in (*os.File).Fd()
+	// we should never run these two tests in parallel
+	mu.Lock()
+	t.Cleanup(mu.Unlock)
+
+	ptmx, pts, err := Open()
+	if err != nil {
+		t.Fatalf("error: open: %v\n", err)
+	}
+	t.Cleanup(func() { _ = ptmx.Close() })
+	t.Cleanup(func() { _ = pts.Close() })
+
+	ctx, done := context.WithCancel(context.Background())
+	go func() {
+		select {
+		case <-ctx.Done():
+			// ptmx.Read() did not block forever, yay!
+		case <-time.After(timeout):
+			_, err := pts.Write([]byte{errMarker}) // unblock ptmx.Read()
+			if err != nil {
+				t.Errorf("failed to write to pts: %v", err)
+			}
+			t.Error("ptmx.Read() was not unblocked")
+			done() // cancel panic()
+		}
+	}()
+	go func() {
+		select {
+		case <-ctx.Done():
+			// Test has either failed or succeeded; it definitely did not hang
+		case <-time.After(timeout * 10 / 9): // timeout +11%
+			panic("ptmx.Read() was not unblocked; avoid hanging forever") // just in case
+		}
+	}()
+	return ptmx, done
+}