Impossible to delete values in array field

[louisremi]

Expected behavior

I have a collection with several array fields:

const schema = Mongoose.Schema({
  _id: { … },
  …
  phones: [{ type: String }],
  websites: [{ type: String }],
  emails: [{ type: String }],
})

The edit UI allows users to add and delete values in this array

When users try to delete values, it fails, the old values reappear after clicking on the save button. It only works if the user replaces the value deleted with a new one.

The issue appears to originate from the flattenRecordDataForUpdates function which turns the value { websites: [ 'https://second-website.com' ] } into { 'websites.0': 'https://second-website.com' } which fails to delete values I want to get rid of. This happens while I didn't add websites to the fieldsToFlatten config of my collection.

Actual behavior

The values deleted by the user should be deleted from the DB

Context

TODO: Please provide any relevant information about your setup.

• Package Version: 8.5.0
• Express Version: ???
• Mongoose Version: 6.0.10
• MongoDB Version: ???

Workaround

As a workaround, I've added the following findOneAndUpdate hook to my Mongoose model:

.pre("findOneAndUpdate", async function () {
    ["websites", "phones", "emails"].forEach((fieldName) => {
      if (this.get(`${fieldName}.0`)) {
        const values = [];
        let val;
        while (
          (val = this.get(`${fieldName}.${values.length}`)) !== undefined
        ) {
          this.set(`${fieldName}.${values.length}`, undefined);
          values.push(val);
        }
        this.set(fieldName, values);
      }
    });
  });