feat: support dot-notation attributes in Filter

src/index.ts

@@ -430,6 +430,9 @@ export type {
   KeysOfAType,
   KeysOfOtherType,
   IsAny,
-  OneOrMore
+  OneOrMore,
+  Join,
+  PropertyType,
+  NestedPaths
 } from './mongo_types';
 export type { serialize, deserialize } from './bson';

src/mongo_types.ts

@@ -56,7 +56,7 @@ export type WithoutId<TSchema> = Omit<TSchema, '_id'>;
 
 /** A MongoDB filter can be some portion of the schema or a set of operators @public */
 export type Filter<TSchema> = {
-  [P in keyof TSchema]?: Condition<TSchema[P]>;
+  [P in Join<NestedPaths<TSchema>, '.'>]?: Condition<PropertyType<TSchema, P>>;
 } & RootFilterOperators<TSchema>;
 
 /** @public */
@@ -422,3 +422,48 @@ export class TypedEventEmitter<Events extends EventsDescription> extends EventEm
 
 /** @public */
 export class CancellationToken extends TypedEventEmitter<{ cancel(): void }> {}
+
+/**
+ * Helper types for dot-notation filter attributes
+ */
+
+/** @public */
+export type Join<T extends unknown[], D extends string> = T extends []
+  ? ''
+  : T extends [string | number]
+  ? `${T[0]}`
+  : T extends [string | number, ...infer R]
+  ? `${T[0]}${D}${Join<R, D>}`
+  : string | number;
+
+/** @public */
+export type PropertyType<Type, Property extends string> = string extends Property
+  ? unknown
+  : Property extends keyof Type
+  ? Type[Property]
+  : Property extends `${infer Key}.${infer Rest}`
+  ? Key extends `${number}`
+    ? Type extends Array<infer ArrayType>
+      ? PropertyType<ArrayType, Rest>
+      : Type extends ReadonlyArray<infer ArrayType>
+      ? PropertyType<ArrayType, Rest>
+      : unknown
+    : Key extends keyof Type
+    ? PropertyType<Type[Key], Rest>
+    : unknown
+  : unknown;
+
+// We dont't support nested circular references
+/** @public */
+export type NestedPaths<Type> = Type extends string | number | boolean | Date | ObjectId
+  ? []
+  : Type extends Array<infer ArrayType>
+  ? [number, ...NestedPaths<ArrayType>]
+  : Type extends ReadonlyArray<infer ArrayType>
+  ? [number, ...NestedPaths<ArrayType>]
+  : // eslint-disable-next-line @typescript-eslint/ban-types
+  Type extends object
+  ? {
+      [Key in Extract<keyof Type, string>]: [Key, ...NestedPaths<Type[Key]>];
+    }[Extract<keyof Type, string>]
+  : [];

test/types/community/collection/filterQuery.test-d.ts

@@ -15,6 +15,11 @@ const db = client.db('test');
  * Test the generic Filter using collection.find<T>() method
  */
 
+interface HumanModel {
+  _id: ObjectId;
+  name: string;
+}
+
 // a collection model for all possible MongoDB BSON types and TypeScript types
 interface PetModel {
   _id: ObjectId; // ObjectId field
@@ -23,14 +28,28 @@ interface PetModel {
   age: number; // number field
   type: 'dog' | 'cat' | 'fish'; // union field
   isCute: boolean; // boolean field
-  bestFriend?: PetModel; // object field (Embedded/Nested Documents)
+  bestFriend?: HumanModel; // object field (Embedded/Nested Documents)
   createdAt: Date; // date field
   treats: string[]; // array of string
   playTimePercent: Decimal128; // bson Decimal128 type
-  readonly friends?: ReadonlyArray<PetModel>; // readonly array of objects
-  playmates?: PetModel[]; // writable array of objects
+  readonly friends?: ReadonlyArray<HumanModel>; // readonly array of objects
+  playmates?: HumanModel[]; // writable array of objects
+  // Object with multiple nested levels
+  meta?: {
+    updatedAt?: Date;
+    deep?: {
+      nested?: {
+        level?: number;
+      };
+    };
+  };
 }
 
+const john = {
+  _id: new ObjectId('577fa2d90c4cc47e31cf4b6a'),
+  name: 'John'
+};
+
 const spot = {
   _id: new ObjectId('577fa2d90c4cc47e31cf4b6f'),
   name: 'Spot',
@@ -78,14 +97,29 @@ expectNotType<Filter<PetModel>>({ age: [23, 43] });
 
 /// it should query __nested document__ fields only by exact match
 // TODO: we currently cannot enforce field order but field order is important for mongo
-await collectionT.find({ bestFriend: spot }).toArray();
+await collectionT.find({ bestFriend: john }).toArray();
 /// nested documents query should contain all required fields
-expectNotType<Filter<PetModel>>({ bestFriend: { family: 'Andersons' } });
+expectNotType<Filter<PetModel>>({ bestFriend: { name: 'Andersons' } });
 /// it should not accept wrong types for nested document fields
 expectNotType<Filter<PetModel>>({ bestFriend: 21 });
 expectNotType<Filter<PetModel>>({ bestFriend: 'Andersons' });
 expectNotType<Filter<PetModel>>({ bestFriend: [spot] });
-expectNotType<Filter<PetModel>>({ bestFriend: [{ family: 'Andersons' }] });
+expectNotType<Filter<PetModel>>({ bestFriend: [{ name: 'Andersons' }] });
+
+/// it should query __nested document__ fields using dot-notation
+collectionT.find({ 'meta.updatedAt': new Date() });
+collectionT.find({ 'meta.deep.nested.level': 123 });
+collectionT.find({ 'friends.0.name': 'John' });
+collectionT.find({ 'playmates.0.name': 'John' });
+/// it should not accept wrong types for nested document fields
+expectNotType<Filter<PetModel>>({ 'meta.updatedAt': 123 });
+expectNotType<Filter<PetModel>>({ 'meta.updatedAt': true });
+expectNotType<Filter<PetModel>>({ 'meta.updatedAt': 'now' });
+expectNotType<Filter<PetModel>>({ 'meta.deep.nested.level': '123' });
+expectNotType<Filter<PetModel>>({ 'meta.deep.nested.level': true });
+expectNotType<Filter<PetModel>>({ 'meta.deep.nested.level': new Date() });
+expectNotType<Filter<PetModel>>({ 'friends.0.name': 123 });
+expectNotType<Filter<PetModel>>({ 'playmates.0.name': 123 });
 
 /// it should query __array__ fields by exact match
 await collectionT.find({ treats: ['kibble', 'bone'] }).toArray();
@@ -227,7 +261,3 @@ await collectionT.find({ playmates: { $elemMatch: { name: 'MrMeow' } } }).toArra
 expectNotType<Filter<PetModel>>({ name: { $all: ['world', 'world'] } });
 expectNotType<Filter<PetModel>>({ age: { $elemMatch: [1, 2] } });
 expectNotType<Filter<PetModel>>({ type: { $size: 2 } });
-
-// dot key case that shows it is assignable even when the referenced key is the wrong type
-expectAssignable<Filter<PetModel>>({ 'bestFriend.name': 23 }); // using dot notation permits any type for the key
-expectNotType<Filter<PetModel>>({ bestFriend: { name: 23 } });