generate-dto.js — DTO generator for TypeORM entities

This repository contains a small Node.js script that automates the creation of Swagger/class-validator DTOs from TypeORM entity files.

Script path

• bin/generate-dto.js

Quick summary

• Purpose: Read one or more .entity.ts files belonging to a module and generate Create and Update DTOs decorated with @ApiPropertyOptional() (Swagger) and class-validator decorators (with validation messages).
• Output: For each parsed entity the script writes two files:
  • create-<entityBaseName>.dto.ts (contains property declarations with @ApiPropertyOptional and validators)
  • update-<entityBaseName>.dto.ts (extends PartialType(CreateXDto))

Requirements

• Node.js (any modern version)
• A NestJS/TypeScript project layout with a src/ folder and entity files named *.entity.ts.
• The project is expected to use (or install) these packages if you want to compile the generated DTOs without changes:
  • @nestjs/swagger
  • class-validator
  • @nestjs/mapped-types (for PartialType)

How it works

• The script accepts a single argument: the module name. Example:

node ./bin/generate-dto.js reserva

• It searches for entity files in common locations and falls back to walking the src/ tree to locate files ending with .entity.ts.
• For each entity file it:
  1. Reads the file and scans lines for property declarations (simple pattern matching for propName: Type;).
  2. Detects some TypeORM relation decorators like @ManyToOne, @OneToMany, @OneToOne, and @ManyToMany and maps them to ID(s) fields (e.g. cliente: Client relation becomes clienteId: number or clienteIds: number[]).
  3. Maps property types to primitive DTO types and validation decorators:
     • string-like types -> string + @IsString({ message: "should be a valid string" })
     • numeric types -> number + @IsNumber({}, { message: "should be a valid number" })
     • boolean -> boolean + @IsBoolean({ message: "should be a valid boolean" })
     • Date-like -> string + @IsDateString({ message: "should be a valid ISO date string" })
     • arrays -> any[] + @IsArray({ message: "should be a valid array" })
     • fallback -> any (no strong validator)
  4. Adds @ApiPropertyOptional() and @IsOptional() for all fields (the generated Create DTOs have optional properties by design in this script) and writes the DTO files to a dto folder near the entity.

Generated file layout If an entity file is located at src/reserva/entities/booking.entity.ts, the script will create (by default):

src/reserva/dto/booking/create-booking.dto.ts
src/reserva/dto/booking/update-booking.dto.ts

Note: the script organizes DTOs into a dto/<entityBaseName>/ subfolder to avoid name collisions when multiple entities exist.

Limitations & parsing details

• The generator uses simple regex-based parsing of the entity source. It works well for straightforward property declarations like:

  id: number;
  name: string;
  created_at: Date;

• It is heuristic-based and may fail or produce suboptimal output for complex TypeScript features, including:

  • computed properties, getters/setters, or methods
  • properties declared using = initializers (the regex expects prop: Type; lines)
  • union/intersection/complex generic types
  • advanced relation patterns or decorator syntax not matched by the relation detector

• Relation handling: when a relation decorator is detected, the script creates an ...Id (or ...Ids) numeric field rather than nested objects. If you prefer nested DTOs or ValidateNested() + Type(() => ...), the script can be extended.

Recommendations & suggested improvements

• Use the TypeScript Compiler API (ts-morph or typescript) for robust AST-based parsing if you need reliable output for complex entities.
• Add flags to the script:
  • --force to overwrite existing DTOs
  • --out <path> to control output folder
  • --nested-relations to produce nested DTOs instead of id fields
• Add tests: generate DTOs into a temporary directory and compile them to detect missing imports or type errors.

Troubleshooting

• If no entities are found, make sure you ran the script from the project root and that src/ exists and contains .entity.ts files.
• If validators or swagger decorators are missing at compile time, install the required packages listed above.

Example

# Generate DTOs for the reservation module
node ./bin/generate-dto.js reserva

# Output (example):
# ✅ DTOs generated for entity 'booking':
#  - src/reserva/dto/booking/create-booking.dto.ts
#  - src/reserva/dto/booking/update-booking.dto.ts

If you'd like, I can now:

• Replace the regex parsing with a TypeScript AST parser for more accurate type extraction.
• Add a --force option and better naming conventions (e.g., put DTOs directly under src/<module>/dto/).