eslint-plugin-class-validator-type-match

ESLint plugin to ensure class-validator decorators match TypeScript type annotations and optional property syntax.

Installation

npm

``bash
npm install --save-dev eslint-plugin-class-validator-type-match
`

yarn

`bash
yarn add -D eslint-plugin-class-validator-type-match
`

Usage

$3

`typescript
import classValidatorTypeMatch from 'eslint-plugin-class-validator-type-match';

export default [classValidatorTypeMatch.flatConfigs.recommended];
`

Or with manual rule configuration:

`typescript
import classValidatorTypeMatch from 'eslint-plugin-class-validator-type-match';

export default [
{
plugins: {
'class-validator-type-match': classValidatorTypeMatch,
},
rules: {
'class-validator-type-match/decorator-type-match': 'error',
'class-validator-type-match/optional-decorator-match': 'error',
'class-validator-type-match/validate-nested-match': 'error',
'class-validator-type-match/type-decorator-match': 'error',
'class-validator-type-match/definite-assignment-match': 'error',
'class-validator-type-match/dto-filename-match': 'error',
},
},
];
`

$3

`javascript
// .eslintrc.js
module.exports = {
extends: ['plugin:class-validator-type-match/recommended'],
};
`

Or with manual rule configuration:

`javascript
// .eslintrc.js
module.exports = {
plugins: ['class-validator-type-match'],
rules: {
'class-validator-type-match/decorator-type-match': 'error',
'class-validator-type-match/optional-decorator-match': 'error',
'class-validator-type-match/validate-nested-match': 'error',
'class-validator-type-match/type-decorator-match': 'error',
'class-validator-type-match/definite-assignment-match': 'error',
'class-validator-type-match/dto-filename-match': 'error',
},
};
`

$3

- recommended - All rules enabled (best for most projects)
- strict - All rules enabled with strict settings
- basic - Only core type matching rules (decorator-type-match, optional-decorator-match, definite-assignment-match, dto-filename-match)

Rules

$3

Ensures class-validator decorators match TypeScript type annotations for primitive types.

Examples:

`typescript
import {IsString, IsNumber, IsBoolean} from 'class-validator';

class User {
@IsString()
name!: number; // ❌ Error: Decorator @IsString does not match type annotation number

@IsNumber()
age!: string; // ❌ Error: Decorator @IsNumber does not match type annotation string

@IsString()
email!: string; // ✅ Correct

@IsBoolean()
isActive!: boolean; // ✅ Correct

@IsString({each: true})
tags!: string[]; // ✅ Correct - validates array elements

@IsString({each: true})
username!: string; // ❌ Error: { each: true } on non-array type
}
`

$3

Ensures @ValidateNested() decorator is correctly applied for complex types.

Examples:

`typescript
import {ValidateNested, IsString} from 'class-validator';

class User {
@ValidateNested()
address!: Address; // ✅ Correct - complex type with @ValidateNested

@ValidateNested({each: true})
addresses!: Address[]; // ✅ Correct - array of complex types with { each: true }

@IsString()
profile!: Profile; // ❌ Error: Complex type requires @ValidateNested()

@ValidateNested()
tags!: string[]; // ❌ Error: Primitive array doesn't need @ValidateNested

@ValidateNested()
history!: Event[]; // ❌ Error: Missing { each: true } for array of complex types
}
`

$3

Ensures @Type(() => ClassName) decorator matches TypeScript type annotations.

Examples:

`typescript
import {Type, ValidateNested} from 'class-validator';

class User {
@Type(() => Address)
@ValidateNested()
address!: Address; // ✅ Correct - @Type matches type

@Type(() => Profile)
@ValidateNested()
address!: Address; // ❌ Error: @Type(() => Profile) doesn't match Address

@ValidateNested()
contact!: Contact; // ❌ Error: Missing @Type(() => Contact)

@Type(() => Item)
@ValidateNested({each: true})
items!: Item[]; // ✅ Correct - @Type matches array element type
}
`

$3

Ensures definite assignment assertion (!) is used correctly with decorators.

Examples:

`typescript
import {IsString, IsOptional} from 'class-validator';

class User {
@IsString()
name!: string; // ✅ Correct - ! can be used for non-optional

@IsString()
email: string; // ✅ Correct - ! is optional for non-optional properties

@IsOptional()
@IsString()
bio?: string; // ✅ Correct - optional property without !

@IsOptional()
@IsString()
username?!: string; // ❌ Error: ! should not be used with optional (?)

@IsString()
nickname!: string = 'default'; // ❌ Error: ! should not be used with initializer

@IsString()
description!: string | undefined; // ❌ Error: ! should not be used with undefined type
}
`

$3

Ensures @IsOptional() decorator usage matches TypeScript optional property syntax (?).

Examples:

`typescript
import {IsOptional, IsString} from 'class-validator';

class User {
@IsOptional()
@IsString()
name?: string; // ✅ Correct - decorator and syntax match

@IsOptional()
@IsString()
email: string; // ❌ Error: Has @IsOptional() but property is not optional

@IsOptional()
@IsString()
phone!: string; // ❌ Error: @IsOptional() conflicts with definite assignment

@IsString()
username?: string; // ❌ Error: Property is optional but missing @IsOptional()
}
`

$3

Ensures DTO class names match their file naming convention.

File Naming Rules:

- Files structured like ..dto.ts (e.g., .body.dto.ts, .query.dto.ts, .param.dto.ts) should have class names ending with Dto (e.g., BodyDto, QueryDto, ParamDto)
- Files structured like .dto.ts should have class names ending with Dto

Examples:

`typescript
// File: create-user.body.dto.ts
import {IsString, IsEmail} from 'class-validator';

export class CreateUserBodyDto {
// ✅ Correct - ends with BodyDto
@IsString()
name!: string;

@IsEmail()
email!: string;
}

// File: create-user.body.dto.ts
export class CreateUserDto {
// ❌ Error: Expected class name to end with "BodyDto"
@IsString()
name!: string;
}

// File: update-profile.query.dto.ts
export class UpdateProfileQueryDto {
// ✅ Correct - ends with QueryDto
@IsString()
filter?: string;
}

// File: user.dto.ts
export class UserDto {
// ✅ Correct - ends with Dto
@IsString()
id!: string;
}

// File: user.dto.ts
export class User {
// ❌ Error: Expected class name to end with "Dto"
@IsString()
id!: string;
}

// File: get-user.param.dto.ts
export class GetUserParamDto {
// ✅ Correct - ends with ParamDto
@IsString()
userId!: string;
}
`

Supported Decorators

$3

- @IsString → string
- @IsNumber / @IsInt / @IsPositive / @IsNegative → number
- @Min / @Max → number
- @IsBoolean → boolean
- @IsArray / @ArrayMinSize / @ArrayMaxSize → array or Array
- @IsDate / @MinDate / @MaxDate → Date
- @IsObject → object
- @IsEnum → enum

$3

The following decorators work with any type and are not checked by decorator-type-match:

- @IsOptional
- @ValidateNested
- @IsDefined
- @IsEmpty
- @IsNotEmpty
- @Equals
- @NotEquals
- @IsIn
- @IsNotIn
- @Type
- @Transform`

License

MIT

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.