Merge pull request #367 from maxekman/345-nil-checks

Fix / Add nil checks for commands/events

Author: maxekman

command_check.go

@@ -15,12 +15,20 @@
 package eventhorizon
 
 import (
+	"errors"
 	"reflect"
 	"time"
 
 	"github.com/looplab/eventhorizon/uuid"
 )
 
+var (
+	// ErrMissingCommand is when there is no command to be handled.
+	ErrMissingCommand = errors.New("missing command")
+	// ErrMissingAggregateID is when a command is missing an aggregate ID.
+	ErrMissingAggregateID = errors.New("missing aggregate ID")
+)
+
 // IsZeroer is used to check if a type is zero-valued, and in that case
 // is not allowed to be used in a command. See CheckCommand.
 type IsZeroer interface {
@@ -39,6 +47,14 @@ func (c *CommandFieldError) Error() string {
 
 // CheckCommand checks a command for errors.
 func CheckCommand(cmd Command) error {
+	if cmd == nil {
+		return ErrMissingCommand
+	}
+
+	if cmd.AggregateID() == uuid.Nil {
+		return ErrMissingAggregateID
+	}
+
 	rv := reflect.Indirect(reflect.ValueOf(cmd))
 	rt := rv.Type()
 

command_check_test.go

@@ -15,6 +15,7 @@
 package eventhorizon
 
 import (
+	"errors"
 	"testing"
 	"time"
 
@@ -28,6 +29,18 @@ func TestCheckCommand(t *testing.T) {
 		t.Error("there should be no error:", err)
 	}
 
+	// Missing command.
+	err = CheckCommand(nil)
+	if !errors.Is(err, ErrMissingCommand) {
+		t.Error("there should be a missing command error:", err)
+	}
+
+	// Missing Aggregate ID.
+	err = CheckCommand(&TestCommandUUIDValue{})
+	if !errors.Is(err, ErrMissingAggregateID) {
+		t.Error("there should be a missing aggregate ID error:", err)
+	}
+
 	// Missing required UUID value.
 	err = CheckCommand(&TestCommandUUIDValue{TestID: uuid.New()})
 	if err == nil || err.Error() != "missing field: Content" {

commandhandler/aggregate/commandhandler.go

@@ -55,8 +55,7 @@ func NewCommandHandler(t eh.AggregateType, store eh.AggregateStore) (*CommandHan
 // HandleCommand handles a command with the registered aggregate.
 // Returns ErrAggregateNotFound if no aggregate could be found.
 func (h *CommandHandler) HandleCommand(ctx context.Context, cmd eh.Command) error {
-	err := eh.CheckCommand(cmd)
-	if err != nil {
+	if err := eh.CheckCommand(cmd); err != nil {
 		return err
 	}
 

commandhandler/bus/commandhandler.go

@@ -45,6 +45,10 @@ func NewCommandHandler() *CommandHandler {
 
 // HandleCommand handles a command with a handler capable of handling it.
 func (h *CommandHandler) HandleCommand(ctx context.Context, cmd eh.Command) error {
+	if err := eh.CheckCommand(cmd); err != nil {
+		return err
+	}
+
 	h.handlersMu.RLock()
 	defer h.handlersMu.RUnlock()
 

eventhandler.go

@@ -16,11 +16,15 @@ package eventhorizon
 
 import (
 	"context"
+	"errors"
 	"reflect"
 	"runtime"
 	"strings"
 )
 
+// ErrMissingEvent is when there is no event to be handled.
+var ErrMissingEvent = errors.New("missing event")
+
 // EventHandlerType is the type of an event handler, used as its unique identifier.
 type EventHandlerType string
 

eventhandler/projector/eventhandler.go

@@ -175,6 +175,13 @@ func (h *EventHandler) HandlerType() eh.EventHandlerType {
 // It will try to find the correct version of the model, waiting for it the projector
 // has the WithWait option set.
 func (h *EventHandler) HandleEvent(ctx context.Context, event eh.Event) error {
+	if event == nil {
+		return &Error{
+			Err:       eh.ErrMissingEvent,
+			Projector: h.projector.ProjectorType().String(),
+		}
+	}
+
 	// Used to retry once in case of a version mismatch.
 	triedOnce := false
 retryOnce:

eventhandler/projector/eventhandler_test.go

@@ -386,6 +386,24 @@ func TestEventHandler_UpdateModelAfterDelete(t *testing.T) {
 	}
 }
 
+func TestEventHandler_MissingEventError(t *testing.T) {
+	repo := &mocks.Repo{}
+	projector := &TestProjector{}
+	handler := NewEventHandler(projector, repo)
+	handler.SetEntityFactory(func() eh.Entity {
+		return &mocks.SimpleModel{}
+	})
+
+	ctx := context.Background()
+
+	err := handler.HandleEvent(ctx, nil)
+
+	projectError := &Error{}
+	if !errors.As(err, &projectError) || !errors.Is(err, eh.ErrMissingEvent) {
+		t.Error("there should be an error:", err)
+	}
+}
+
 func TestEventHandler_LoadError(t *testing.T) {
 	repo := &mocks.Repo{}
 	projector := &TestProjector{}

eventhandler/saga/eventhandler.go

@@ -87,6 +87,13 @@ func (h *EventHandler) HandlerType() eh.EventHandlerType {
 
 // HandleEvent implements the HandleEvent method of the eventhorizon.EventHandler interface.
 func (h *EventHandler) HandleEvent(ctx context.Context, event eh.Event) error {
+	if event == nil {
+		return &Error{
+			Err:  eh.ErrMissingEvent,
+			Saga: h.saga.SagaType().String(),
+		}
+	}
+
 	// Run the saga which can issue commands on the provided command handler.
 	if err := h.saga.RunSaga(ctx, event, h.commandHandler); err != nil {
 		return &Error{

eventhandler/saga/eventhandler_test.go

@@ -16,6 +16,7 @@ package saga
 
 import (
 	"context"
+	"errors"
 	"reflect"
 	"testing"
 	"time"
@@ -52,6 +53,23 @@ func TestEventHandler(t *testing.T) {
 	}
 }
 
+func TestEventHandler_MissingEventError(t *testing.T) {
+	commandHandler := &mocks.CommandHandler{
+		Commands: []eh.Command{},
+	}
+	saga := &TestSaga{}
+	handler := NewEventHandler(saga, commandHandler)
+
+	ctx := context.Background()
+
+	err := handler.HandleEvent(ctx, nil)
+
+	projectError := &Error{}
+	if !errors.As(err, &projectError) || !errors.Is(err, eh.ErrMissingEvent) {
+		t.Error("there should be an error:", err)
+	}
+}
+
 const (
 	TestSagaType Type = "TestSaga"
 )

eventhandler/waiter/eventhandler.go

@@ -51,6 +51,10 @@ func (h *EventHandler) HandlerType() eh.EventHandlerType {
 // HandleEvent implements the HandleEvent method of the eventhorizon.EventHandler interface.
 // It forwards events to the waiters so that they can match the events.
 func (h *EventHandler) HandleEvent(ctx context.Context, event eh.Event) error {
+	if event == nil {
+		return eh.ErrMissingEvent
+	}
+
 	h.inbox <- event
 
 	return nil