Provide a hook for dealing with file uploads or a dedicated CollectionAfterCreateHook

[mortocks]

Background

We have a collection where users upload images which need to be moderated. As a first pass we're wanting AI to attempt moderation just to reduce the workload for the moderation team.

Ideally this kind of work would be done in the CollectionBeforeChangeHook hook but since the collection has a file upload, we need to wait until the file as actually been uploaded before we can do anything with it, so we have to move the work to the CollectionAfterChangeHook hook.

Unfortunately, we can't directly modify the record and return it like we can in the CollectionBeforeChangeHook so we have to manually update the record using the req.payload object.

Here's an pseudo example of the current implementation;

const afterChangeHook: CollectionAfterChangeHook<Submission> = async ({
    doc,
    operation,
    req
}) => {

    // Only for new documents that haven't been moderated by a human
    if (operation !== 'create' || doc.approved !== 'pending') {
        return doc
    }

    try {
        // Get the url of the image and send it to AI for moderation
        const url = `${process.env.VERCEL_URL}/${doc.url}`;
        const results = await moderateImageWithAi(url);

        // Attempt to update the document with the results
        // 💥 File is not found
        const newDoc = await req.payload.update({
            collection: 'submissions',
            id: doc.id, // 💥 The original id but I'm assuming that the doc hasn't been written yet (even though we have an id?)
            data: {
                approved: results.status;
            }
        });
        return newDoc

    } catch (error) {
        console.log(error)
        return doc;
    }
};

The issue is that while the hook is called CollectionAfterChangeHook, we're assuming that technically the record hasn't been written in the database yet so calling update returns NOT FOUND error, however if we try to use the create function to manually create the record, the file's won't get uploaded and we get the error MissingFile: No files were uploaded.

Potential solutions

1. Provide a dedicated hook called CollectionAfterCreate which behaves like the CollectionAfterChangeHook but is called after the record is written to the db but runs before the document is returned.

2. Alternately, let records be updated via the CollectionAfterChangeHook by just returning the shape (although I can see how this would cause confusion to the correct use case for this hook so it's probably not ideal and cause confusion as to when to write to the db

3. Provide a hook that runs after file uploads happens, something like CollectionAfterFileUpload . I think this would be the most complicated both from implementation and from an API for the user

4. Provide a some way of dealing with the image data in the CollectionBeforeChange hook. Currently we just get file information and not the actual image - again I think this solution is probably not idea.

Primary cause

I think the API of hooks is really powerful and works in most data use-cases, it's just because there are file uploads that the order of events becomes difficult to create this kind of functionality. As a short term solution we're moving to cron jobs but using payloads hooks would be a much more elegant solution.

Would also move to hear that we're doing something wrong and there is a solution in the current API 😉

[mortocks]

Note - I've also tried the above making the hook synchronous to work around this issue, but while I don't get an "Unfound" error, the document doesn't updating. Im assuming this is some kind of race condition where the original update is happening after my change or something.

[DanRibbens]

Hey @mortocks,

You can use the collection afterChangeHook exactly as you intended to do so. The reason the payload.update cannot find that record is because the transaction hasn't been committed. The simple fix for that is that you need to pass the req through from your hook to any local API calls. This is necessary to use the DB within the same transaction and have access to the record pre-commit.

There isn't anything else you should need to do, as long as the update works the entire change is committed all at once.

Let me know if you have any trouble!