post deleteMany/deleteOne middleware not being called mongoose

Question

So, I'm trying to delete many documents at once, and for some reason, the post middleware works for document.deleteOne(), but not for Model.deleteMany(). Specifically, I am looking for a fix for it not firing for Lecture.deleteMany(...) and Chapter.deleteMany(...). Note that the documents themselves do end up being deleted.

Here is the response handler for one of my routes:

export const DELETE = catchAsync(async function (req, { params }) {
  // Check if course exists
  const course = await Course.findById(params.id).populate({
    path: "chapters",
    select: { id: 1 },
  });
  if (!course)
    return new AppError("No courses found with the provided id", 404);

  const { chapters } = course;
  const chapterIds = chapters.map((chapter) => chapter.id);

  // Delete course's lectures
  await Lecture.deleteMany({ chapter: { $in: chapterIds } });

  // Delete course's chapters
  await Chapter.deleteMany({ _id: { $in: chapterIds } }); // Specifically this one

  // Delete course
  await course.deleteOne();
});

And here is the post middleware in my chapter model file (very similar to lecture):

chapterSchema.post(
  ["deleteOne", "deleteMany"],
  { document: true },
  async function (doc, next) {
    console.log("POST DELETE ONE CHAPTER");

    const course = await Course.findById(this.course);

    // Find and remove chapter from course
    const index = course.chapters.findIndex((ch) => ch._id === doc._id);
    course.chapters.splice(index, 1);
    await course.save();

    next();
  }
);

Answer 1

I figured it out. I believe post is a document middleware, and since Model.deleteMany() is a query, the middleware does not get called. I changed my code the one below.

chapterSchema.post("deleteOne", { document: true }, async function (doc, next) {
  console.log("Removing chapter from its course");

  // Find course
  const course = await Course.findById(doc.course);
  if (!course) return next();

  // Find and remove chapter from course
  const index = course.chapters.findIndex((ch) => ch._id === doc._id);
  course.chapters.splice(index, 1);
  await course.save();

  next();
});