Mongoose Schema validation issues when using Array of Mixed [{ }] - node.js

Question

I am building a schema in mongoose (v4.13.8) with an Array of Mixed values. I have come up with the following Schema:
var deviceConfigSchema = new mongoose.Schema({
capabilities: {
type: [capabilitySchema],
required: true,
validator: [isValidCapabilities, "Not a valid capability array"]
},
services: {
type: [{}],
required: true,
validator: [isValidServices, "Not a valid service array"]
}
});
The problem is that I get a validation error saying that services: Path 'services' is required. when I try to submit data. What is strange is that the data I send for the 'capabilities' works fine and the only difference is that I specify a schema explicitly.
Removing the required: true from services causes there to be an empty array object in the returned values.
I am submitting the data using an API POST request with the data in the body of the request. I am using Postman to submit the request, with x-www-form-urlencoded checked. This is copied from the body key-value input
capabilities[0][field_map][field]:pressure
capabilities[0][field_map][type]:float
capabilities[0][field_map][format]:hPa
services[0][name]:rest
services[0][receive][0][capability_id]:0
services[0][receive][0][path]:/api/relay/0
Update:
I'd like to apologise as this was a mistake on my part. I dynamically create a configuration based on the request and at one point the copied services were being made null, doh!
However, having got the required: true validation to pass, the custom validator is still not being executed. I also can't find any documentation about the order in which validators and are executed which would be very useful. Below is the validator snippet for reference:
function isValidServices(services) {
for (const service of services) {
if (typeof service.name !== 'string') return false;
}
return true;
}

Answer 1

Having experimented with various approaches and looking in more detail on the mongoose API docs, I found that there is a validate option for schemas too. http://mongoosejs.com/docs/api.html#schematype_SchemaType-validate
I changed my Schema from this:
var deviceConfigSchema = new mongoose.Schema({
capabilities: {
type: [capabilitySchema],
required: true,
validator: [isValidCapabilities, "Not a valid capability array"]
},
services: {
type: [{}],
required: true,
validator: [isValidServices, "Not a valid service array"]
}
});
To this [notice the validate instead of validator]...
var deviceConfigSchema = new mongoose.Schema({
capabilities: {
type: [capabilitySchema],
required: true,
validate: [isValidCapabilities, "Not a valid capability array"]
},
services: {
type: [{}],
required: true,
validate: [isValidServices, "Not a valid service array"]
}
});
After this my validator functions were being executed without any issues. Hopefully this helps someone.