Nil pointer dereference in waitForPluginLoad closes #4752 (#4896)

* Add test for #4752: Nil pointer dereference in waitForPluginLoad

This test demonstrates the bug where waitForPluginLoad() panics with a nil
pointer dereference when a plugin fails during startup before the reattach
config is set.

The test creates a runningPlugin with reattach=nil and closes the failed
channel, simulating a plugin that fails in startPluginProcess before
initializePlugin is called.

* Fix #4752: Add nil check for reattach in waitForPluginLoad

Adds a nil pointer check before accessing p.reattach.Pid when a plugin
fails during startup. If the plugin fails before the reattach config is
set (e.g., in startPluginProcess), reattach will be nil and the code
would previously panic when trying to log the PID.

The fix checks if reattach is nil and logs an appropriate message in
each case, preventing the panic while still providing useful debugging
information.

pkg/pluginmanager_service/plugin_manager.go

@@ -701,7 +701,12 @@ func (m *PluginManager) waitForPluginLoad(p *runningPlugin, req *pb.GetRequest)
 	case <-p.initialized:
 		log.Printf("[TRACE] plugin initialized: pid %d (%p)", p.reattach.Pid, req)
 	case <-p.failed:
-		log.Printf("[TRACE] plugin pid %d failed %s (%p)", p.reattach.Pid, p.error.Error(), req)
+		// reattach may be nil if plugin failed before it was set
+		if p.reattach != nil {
+			log.Printf("[TRACE] plugin pid %d failed %s (%p)", p.reattach.Pid, p.error.Error(), req)
+		} else {
+			log.Printf("[TRACE] plugin %s failed before reattach was set: %s (%p)", p.pluginInstance, p.error.Error(), req)
+		}
 		// get error from running plugin
 		return p.error
 	}

pkg/pluginmanager_service/plugin_manager_test.go

@@ -773,3 +773,46 @@ func TestPluginManager_Shutdown_NoPlugins(t *testing.T) {
 		t.Error("Shutdown returned nil response")
 	}
 }
+
+// TestWaitForPluginLoadWithNilReattach tests that waitForPluginLoad handles
+// the case where a plugin fails before reattach is set.
+// This reproduces bug #4752 - a nil pointer panic when trying to log p.reattach.Pid
+// after the plugin fails during startup before the reattach config is set.
+func TestWaitForPluginLoadWithNilReattach(t *testing.T) {
+	pm := newTestPluginManager(t)
+
+	// Add plugin config required by waitForPluginLoad with a reasonable timeout
+	timeout := 30 // Set timeout to 30 seconds so test doesn't time out immediately
+	pm.plugins["test-instance"] = &plugin.Plugin{
+		Plugin:        "test-plugin",
+		Instance:      "test-instance",
+		StartTimeout:  &timeout,
+	}
+
+	// Create a runningPlugin that simulates a plugin that failed before reattach was set
+	rp := &runningPlugin{
+		pluginInstance: "test-instance",
+		initialized:    make(chan struct{}),
+		failed:         make(chan struct{}),
+		error:          fmt.Errorf("plugin startup failed"),
+		reattach:       nil, // Explicitly nil - this is the bug condition
+	}
+
+	// Simulate plugin failure by closing the failed channel in a goroutine
+	go func() {
+		time.Sleep(10 * time.Millisecond)
+		close(rp.failed)
+	}()
+
+	// Create a dummy request
+	req := &pb.GetRequest{
+		Connections: []string{"test-conn"},
+	}
+
+	// This should panic with nil pointer dereference when trying to log p.reattach.Pid
+	err := pm.waitForPluginLoad(rp, req)
+
+	// We expect an error (the plugin failed), but we should NOT panic
+	assert.Error(t, err)
+	assert.Contains(t, err.Error(), "plugin startup failed")
+}