Is there a correct way to remove node/relationship properties?

[Ansis100]

Neo4j does not support null as a property value. This also means that the union type Neo4jSupportedProperties does not contain null. However, the model validator accepts null and model TypeScript definitions can be set to property?: null | type.

This mostly works and successfully removes the property, excluding some weird edge cases. For example, if the revalidator schema is set to 'type' instead of ['null', 'type'], then updating the object using the model static will work fine, however, updating using instance.property = value and instance.save() will cause a validation error.

If this is the intended usage, it would be nice to specify this in the docs and maybe add null to Neo4jSupportedProperties to avoid some TypeScript weirdness when using Neogma TS generics. If not, then it might be useful to add some kind of specific property removing mechanism to modifying methods.

[Ansis100]

#80 seems to be relevant here. Adding support for null values would "fix" this workaround, and leave us with no way of removing properties. I guess it depends on whether or not you consider null and undefined the same thing in the Neo4j context.

[Ansis100]

@themetalfleece do you have some sort of plan for implementing this? If you could provide some sort of spec on how you imagine this might be implemented, I would gladly create a PR.

I imagine something like another property on the second update model static parameter params:

    update: (data: Partial<Properties>, params?: GenericConfiguration & {
        where?: WhereParamsI;
        /** defaults to false. Whether to return the properties of the nodes after the update. If it's false, the first entry of the return value of this function will be an empty array */
        return?: boolean;
        removeProperties?: string[]; // This is new!
    }) => Promise<[Instance[], QueryResult]>;

Even better if there's some type checking where the removeProperties array only accepts model property keys as values.

This, however, does not provide a way to remove properties from an instance. That could be fixed by creating a new instance method removeProperties(propertyKeys: string[]) which somehow lets save() know that these properties should be removed.

We could just lean on the fact that null values already remove the properties and fix any Typescript or validation issues that arise from that, but I have a feeling that an explicit removeProperties is less ambiguous.

[themetalfleece]

Hey, thanks for offering to create a PR for this!

I was thinking that we could add an operator, which would be used like this:

user.update({
  name: 'Bob',
  age: { [Op.remove]: true }
});

What do you think of this? :)

I'm also ok with adding proper support for null and have it remove the properties.

[Ansis100]

I wouldn't have guessed that we can use the operators like that, but that looks even better than my proposal!
I'll get on that and try to figure it out.

[themetalfleece]

Cheers! Right now the operators are used for "Where" only (for finding), but we can definitely use them (or a new set of operators) for setting/updating values.
So, it makes sense to rename the existing Op object to WhereOp (or, create a new one for backwards compability), and add a new one called SetOp/UpdateOp or something similar, which will have the remove operator? 🤔 That way, the two types of operators won't be mixed together.