Recalculate E-Tag right before before storing items

E-tags used to be set after parsing an item only, before potential hooks
alter the item content. This change adds a final step to resource Update
and Create operations to recalculate E-tags right before passing items
to the Storer back-end.

Fixes #255

Author: Dragomir-Ivanov

resource/resource.go

@@ -354,12 +354,32 @@ func (r *Resource) Insert(ctx context.Context, items []*Item) (err error) {
 		}(time.Now())
 	}
 	if err = r.hooks.onInsert(ctx, items); err == nil {
-		err = r.storage.Insert(ctx, items)
+		if err = recalcEtag(items); err == nil {
+			err = r.storage.Insert(ctx, items)
+		}
 	}
 	r.hooks.onInserted(ctx, items, &err)
 	return
 }
 
+func recalcEtag(items []*Item) error {
+	if items == nil {
+		return nil
+	}
+
+	for _, v := range items {
+		if v == nil {
+			continue
+		}
+		etag, err := genEtag(v.Payload)
+		if err != nil {
+			return err
+		}
+		v.ETag = etag
+	}
+	return nil
+}
+
 // Update implements Storer interface.
 func (r *Resource) Update(ctx context.Context, item *Item, original *Item) (err error) {
 	if LoggerLevel <= LogLevelDebug && Logger != nil {
@@ -371,7 +391,9 @@ func (r *Resource) Update(ctx context.Context, item *Item, original *Item) (err
 		}(time.Now())
 	}
 	if err = r.hooks.onUpdate(ctx, item, original); err == nil {
-		err = r.storage.Update(ctx, item, original)
+		if err = recalcEtag([]*Item{item}); err == nil {
+			err = r.storage.Update(ctx, item, original)
+		}
 	}
 	r.hooks.onUpdated(ctx, item, original, &err)
 	return

resource/resource_crud_test.go

@@ -491,7 +491,7 @@ func TestResourceInsert(t *testing.T) {
 	}))
 	r.Use(InsertedEventHandlerFunc(func(ctx context.Context, items []*Item, err *error) {
 		postHook = true
-		assert.Equal(t, []*Item{{ID: 1}}, items)
+		assert.Equal(t, []*Item{{ID: 1, ETag: "37a6259cc0c1dae299a7866489dff0bd"}}, items)
 		assert.NoError(t, *err)
 	}))
 	ctx := context.Background()
@@ -518,7 +518,7 @@ func TestResourceInsertError(t *testing.T) {
 	}))
 	r.Use(InsertedEventHandlerFunc(func(ctx context.Context, items []*Item, err *error) {
 		postHook = true
-		assert.Equal(t, []*Item{{ID: 1}}, items)
+		assert.Equal(t, []*Item{{ID: 1, ETag: "37a6259cc0c1dae299a7866489dff0bd"}}, items)
 		assert.EqualError(t, *err, "storer error")
 	}))
 	ctx := context.Background()
@@ -571,7 +571,7 @@ func TestResourceInsertPostHookError(t *testing.T) {
 	}))
 	r.Use(InsertedEventHandlerFunc(func(ctx context.Context, items []*Item, err *error) {
 		postHook = true
-		assert.Equal(t, []*Item{{ID: 1}}, items)
+		assert.Equal(t, []*Item{{ID: 1, ETag: "37a6259cc0c1dae299a7866489dff0bd"}}, items)
 		assert.NoError(t, *err)
 		*err = errors.New("post hook error")
 	}))
@@ -604,7 +604,7 @@ func TestResourceUpdate(t *testing.T) {
 	}))
 	r.Use(UpdatedEventHandlerFunc(func(ctx context.Context, item *Item, origin *Item, err *error) {
 		postHook = true
-		assert.Equal(t, &Item{ID: 1}, item)
+		assert.Equal(t, &Item{ID: 1, ETag: "37a6259cc0c1dae299a7866489dff0bd"}, item)
 		assert.Equal(t, &Item{ID: 1}, origin)
 		assert.NoError(t, *err)
 	}))
@@ -633,7 +633,7 @@ func TestResourceUpdateError(t *testing.T) {
 	}))
 	r.Use(UpdatedEventHandlerFunc(func(ctx context.Context, item *Item, origin *Item, err *error) {
 		postHook = true
-		assert.Equal(t, &Item{ID: 1}, item)
+		assert.Equal(t, &Item{ID: 1, ETag: "37a6259cc0c1dae299a7866489dff0bd"}, item)
 		assert.Equal(t, &Item{ID: 1}, origin)
 		assert.EqualError(t, *err, "storer error")
 	}))
@@ -691,7 +691,7 @@ func TestResourceUpdatePostHookError(t *testing.T) {
 	}))
 	r.Use(UpdatedEventHandlerFunc(func(ctx context.Context, item *Item, origin *Item, err *error) {
 		postHook = true
-		assert.Equal(t, &Item{ID: 1}, item)
+		assert.Equal(t, &Item{ID: 1, ETag: "37a6259cc0c1dae299a7866489dff0bd"}, item)
 		assert.Equal(t, &Item{ID: 1}, origin)
 		assert.NoError(t, *err)
 		*err = errors.New("post hook error")