Description
openedon May 5, 2024
Prerequisites
- I have written a descriptive issue title
- I have searched existing issues to ensure the bug has not already been reported
Mongoose version
8.3.3
Node.js version
18.8.0
MongoDB server version
7.0
Typescript version (if applicable)
4.5.2
Description
Mongoose doesn't clone the source when using merge, so filter query inputs that have objects for values at the top level are modified in place by query modifiers like .and, .or, .where, etc., and those changes persist because of JS's call-by-sharing.
This is such core behavior that maybe we're doing it on purpose, but I find it unintuitive that Mongoose is taking my filter input and mutating it so it might end up as something else when I go to use the same input.
Is there a reason we don't just do source = clone(source) or something at the top of Query.prototype.merge to protect against errant mutations? Is it a performance thing?
Fundamentally, this is the specific problem line. When a key in from doesn't exist in to, we just copy over the entire value from from into to. When that value is an object itself, it's just an address in memory, so it's literally the same object that gets copied. Later on, when the query is mutating its own conditions (rightfully so), this means that the initial externally-provided query also gets changed.
Steps to Reproduce
export const queryMergeDemo = async (): Promise<$TSFixMe> => {
/********************************* SETUP *********************************/
type Person = {
_id: mongoose.Types.ObjectId;
name: string;
age: number;
active: boolean;
createdAt: number;
updatedAt: number;
};
const schema = new mongoose.Schema<Person>({
name: { type: String, required: true },
age: { type: Number, required: true },
active: { type: Boolean, required: true, default: true },
createdAt: { type: Number },
updatedAt: { type: Number },
});
const M = mongoose.model<Person>("Person", schema);
await M.create([
{ name: "Alice", age: 30 },
{ name: "Bob", age: 27 },
{ name: "Charlie", age: 25 },
{ name: "David", age: 8 },
{ name: "Eve", age: 20, active: false },
]);
/********************************* EXAMPLE #1 *********************************/
const activeQuery: FilterQuery<Person> = { $and: [{ active: true }] };
const activeAdults = await M.countDocuments(activeQuery)
.and([{ age: { $gte: 18 } }])
.exec();
// EXPECTED: activeAdults === 3
// ACTUAL: activeAdults === 3
const allActive = await M.countDocuments(activeQuery).exec();
// EXPECTED: allActive === 4
// ACTUAL: allActive === 3
/********************************* EXAMPLE #2 *********************************/
const adultQuery: FilterQuery<Person> = { age: { $gte: 18 } };
const youngAdults = await M.countDocuments(adultQuery).where("age").lte(25).exec();
// EXPECTED: youngAdults === 2
// ACTUAL: youngAdults === 2
const allAdults = await M.countDocuments(adultQuery).exec();
// EXPECTED: allAdults === 4
// ACTUAL: allAdults === 2
/********************************* CLEANUP *********************************/
await M.db.dropCollection("people");
return { activeAdults, allActive, youngAdults, allAdults };
};Expected Behavior
See comments in the code block above for two different examples with expectation vs actual.