types: allow [true, string] for unique

Author: vkarpov15

test/types/schema.test.ts

@@ -101,6 +101,7 @@ movieSchema.index({ title: 'text' }, {
 });
 movieSchema.index({ rating: -1 });
 movieSchema.index({ title: 1 }, { unique: true });
+movieSchema.index({ title: 1 }, { unique: [true, 'Title must be unique'] as const });
 movieSchema.index({ tile: 'ascending' });
 movieSchema.index({ tile: 'asc' });
 movieSchema.index({ tile: 'descending' });

types/index.d.ts

@@ -309,7 +309,7 @@ declare module 'mongoose' {
     eachPath(fn: (path: string, type: SchemaType) => void): this;
 
     /** Defines an index (most likely compound) for this schema. */
-    index(fields: IndexDefinition, options?: IndexOptions): this;
+    index(fields: IndexDefinition, options?: Omit<IndexOptions, 'unique'> & { unique?: boolean | undefined | [true, string] }): this;
 
     /**
      * Define a search index for this schema.

types/indexes.d.ts

@@ -63,7 +63,7 @@ declare module 'mongoose' {
   type ConnectionSyncIndexesResult = Record<string, OneCollectionSyncIndexesResult>;
   type OneCollectionSyncIndexesResult = Array<string> & mongodb.MongoServerError;
 
-  interface IndexOptions extends mongodb.CreateIndexesOptions {
+  type IndexOptions = Omit<mongodb.CreateIndexesOptions, 'expires' | 'weights' | 'unique'> & {
     /**
      * `expires` utilizes the `ms` module from [guille](https://github.com/guille/) allowing us to use a friendlier syntax:
      *
@@ -86,7 +86,9 @@ declare module 'mongoose' {
      */
     expires?: number | string;
     weights?: Record<string, number>;
-  }
+
+    unique?: boolean | [true, string]
+  };
 
   type SearchIndexDescription = mongodb.SearchIndexDescription;
 }

types/schematypes.d.ts

@@ -111,7 +111,7 @@ declare module 'mongoose' {
      * will build a unique index on this path when the
      * model is compiled. [The `unique` option is **not** a validator](/docs/validation.html#the-unique-option-is-not-a-validator).
      */
-    unique?: boolean | number;
+    unique?: boolean | number | [true, string];
 
     /**
      * If [truthy](https://masteringjs.io/tutorials/fundamentals/truthy), Mongoose will