Failure when adding many-to-many association

[pcnova]

Description

We're encountering the following error when trying to add a new many-to-many association between two entities:

TypeError: Cannot read property 'constructor' of undefined

To be clear, we are not tracking changes on these entities (no @TrackChanges decorator), so getting an error from nestjs-changelog is quite unexpected. After some investigation, I figured out that the problem is a missing check for whether an entity is included in the event that notifies of a new insertion, here:

nestjs-changelog/lib/change.subscriber.ts

Line 26 in b129bd2

if (Reflect.hasMetadata("__track_changes", event.entity.constructor)) {

So this problem will be seen anytime there's something being inserted into the database which has not been marked with the @Entity decorator, as is the case for the join table created by TypeORM for a many-to-many relationship.

Workaround

One possibility, at least for this case, is to explicitly define an entity class for the join table (i.e., don't let TypeORM create it), which means you'll add the @Entity decorator, getting rid of the problem. However, this is not a simple change.

The easiest way I found around this is to use ChangeSubscriber.disableTracking to wrap the save() call. But of course, this may not be desirable if you are saving things that you want tracking on.