How to Enforce Strict Typing with Cursor

1---
2description: Enforce strict typing in NestJS code
3globs: "*.ts"
4alwaysApply: true
5---
6
7# NestJS Strict Typing Rules
8
9## TypeScript:
10- NEVER use 'any' type — use 'unknown' and narrow, or define proper types
11- NEVER use type assertions (as) unless narrowing from unknown
12- ALWAYS use explicit return types on all public methods
13- ALWAYS enable strict mode patterns: strictNullChecks, noImplicitAny
14
15## DTOs:
16- ALWAYS use class-validator decorators on every DTO property
17- ALWAYS use class-transformer @Type() for nested objects
18- ALWAYS use @ApiProperty() from @nestjs/swagger on DTO properties
19- ALWAYS create separate CreateDto, UpdateDto (with PartialType), ResponseDto
20- Use readonly properties in response DTOs
21
22## Entities:
23- ALWAYS use TypeORM decorators: @Entity, @Column, @PrimaryGeneratedColumn
24- ALWAYS specify column types explicitly: @Column({ type: 'varchar', length: 255 })
25- ALWAYS define relations with explicit types and decorators
26
27## Services:
28- ALWAYS define return types as Promise<EntityType> or Promise<EntityType[]>
29- ALWAYS handle null returns explicitly with proper error throwing
30- Use custom exception classes extending HttpException

1@nestjs-typing.mdc @src/users/entities/user.entity.ts
2
3Create a complete Product module following the exact same patterns
4as the User entity. Include:
51. product.entity.ts — TypeORM entity with proper column types
62. create-product.dto.ts — with class-validator decorators
73. update-product.dto.ts — using PartialType(CreateProductDto)
84. product-response.dto.ts — readonly response with @ApiProperty
95. products.service.ts — with explicit Promise return types
106. products.controller.ts — with full Swagger decorators
11
12The Product has: id (uuid), name (string 255), price (decimal),
13category (string 100), isActive (boolean), createdAt, updatedAt.

1Add strict typing, class-validator decorators, and @ApiProperty to this
2NestJS DTO. Every string needs @IsString() and @MaxLength().
3Every number needs @IsNumber() and @Min/@Max.
4Optional fields need @IsOptional(). Nested objects need @ValidateNested()
5and @Type(). Add @ApiProperty with description and example for each field.

1@nestjs-typing.mdc @codebase
2
3Audit this NestJS project for type safety issues. Find and list:
41. Any use of 'any' type in services, controllers, or DTOs
52. DTO properties missing class-validator decorators
63. Service methods without explicit Promise return types
74. Entity columns without explicit type definitions
85. Controllers missing @ApiResponse decorators
9
10For each issue, show the file, line, and the corrected version.

1---
2description: Generate a type-safe NestJS DTO set
3---
4
5Generate a complete set of NestJS DTOs for the entity described by the user.
6
7Follow these rules:
81. CreateDto — all required fields with class-validator decorators
92. UpdateDto — extends PartialType(CreateDto)
103. ResponseDto — readonly fields with @Exclude() for sensitive data
114. QueryDto — optional filter parameters with @IsOptional()
12
13Every property must have:
14- @ApiProperty() with description and example
15- Appropriate class-validator decorator
16- Explicit TypeScript type (never any)
17
18Reference @nestjs-typing.mdc for full conventions.