From a176c791740405089a1818574bd514e94c70c54b Mon Sep 17 00:00:00 2001
From: Callan Barrett <callan@zoocar.org>
Date: Sat, 17 Jan 2026 22:42:33 +0800
Subject: [PATCH] fix: don't fire OnCardRemoved on fatal communication errors

When the PN532 device is unplugged or experiences a fatal error,
the library was incorrectly firing OnCardRemoved before
OnDeviceDisconnected. This gives callers false information - the
card wasn't removed, the reader disconnected.

Now handlePollingError() checks for fatal errors first and returns
early after calling OnDeviceDisconnected, skipping handleCardRemoval().
---
 polling/session.go      |  9 +++++----
 polling/session_test.go | 36 ++++++++++++++++++++++++++++++++++++
 2 files changed, 41 insertions(+), 4 deletions(-)

diff --git a/polling/session.go b/polling/session.go
index b3f0b10..669de42 100644
--- a/polling/session.go
+++ b/polling/session.go
@@ -636,11 +636,8 @@ func (s *Session) handlePollingError(err error) {
 		return
 	}
 
-	// For serious device errors, trigger immediate card removal
-	// This handles cases like device disconnection
-	s.handleCardRemoval()
-
 	// If this is a fatal error (device disconnected), notify via callback
+	// but do NOT trigger card removal - the card wasn't removed, the reader was
 	if pn532.IsFatal(err) {
 		s.stateMutex.RLock()
 		onDisconnected := s.OnDeviceDisconnected
@@ -649,7 +646,11 @@ func (s *Session) handlePollingError(err error) {
 		if onDisconnected != nil {
 			onDisconnected(err)
 		}
+		return
 	}
+
+	// For non-fatal errors, trigger card removal (transient comm issues)
+	s.handleCardRemoval()
 }
 
 // handleCardRemoval handles card removal state changes
diff --git a/polling/session_test.go b/polling/session_test.go
index e5f9d22..001dc2a 100644
--- a/polling/session_test.go
+++ b/polling/session_test.go
@@ -1281,6 +1281,42 @@ func TestSession_OnDeviceDisconnected(t *testing.T) {
 	})
 }
 
+// TestSession_FatalErrorDoesNotTriggerCardRemoved verifies that fatal errors
+// (device disconnection) don't incorrectly fire OnCardRemoved before OnDeviceDisconnected.
+func TestSession_FatalErrorDoesNotTriggerCardRemoved(t *testing.T) {
+	t.Parallel()
+	device, _ := createMockDeviceWithTransport(t)
+	session := NewSession(device, nil)
+
+	// Simulate card was present
+	session.stateMutex.Lock()
+	session.state.Present = true
+	session.state.LastUID = "04123456789ABC"
+	session.stateMutex.Unlock()
+
+	var cardRemovedCalled bool
+	var disconnectedCalled bool
+	session.SetOnCardRemoved(func() {
+		cardRemovedCalled = true
+	})
+	session.SetOnDeviceDisconnected(func(_ error) {
+		disconnectedCalled = true
+	})
+
+	// Create a fatal error (device disconnected)
+	fatalErr := &pn532.TransportError{
+		Op:   "test",
+		Port: "test",
+		Err:  pn532.ErrDeviceNotFound,
+		Type: pn532.ErrorTypePermanent,
+	}
+
+	session.handlePollingError(fatalErr)
+
+	assert.True(t, disconnectedCalled, "OnDeviceDisconnected should be called")
+	assert.False(t, cardRemovedCalled, "OnCardRemoved should NOT be called for fatal errors")
+}
+
 func TestSession_HandleCardRemoval(t *testing.T) {
 	t.Parallel()