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Eslint rules for nestjs projects

Package Exports

  • @darraghor/eslint-plugin-nestjs-typed

This package does not declare an exports field, so the exports above have been automatically detected and optimized by JSPM instead. If any package subpath is missing, it is recommended to post an issue to the original package (@darraghor/eslint-plugin-nestjs-typed) to support the "exports" field. If that is not possible, create a JSPM override to customize the exports field for this package.

Readme

Some eslint rules for working with NestJs projects

Why

Nest Dependency Injection

There are some things you don't want to forget when working with Nest dependency injection.

The Nest DI is declarative and if you forget to provide an injectable you wont see an error until run time.

If you're using custom providers the errors can be really tricky to figure out because they won't explicitly error about mismatched injected items, you will just get unexpected operation.

Open Api / Swagger and automatically generating a client for front end

When working with NestJS I generate my front end models using the swagger generated from the nest controllers and models. I have a bunch of rules that are mostly for strict typing for those controllers and models.

They are somewhat opinionated but necessary for clean model generation if using an Open Api model generator.

Rule list (more details for each rule below)

Nest Modules

  • provided-injected-should-match-factory-parameters
  • injectable-should-be-provided

Nest Swagger

  • api-property-matches-property-optionality
  • controllers-should-supply-api-tags
  • api-method-should-specify-api-operation

To install

npm install --save-dev @darraghor/eslint-plugin-nestjs-typed

Then update your eslint with the plugin import and add the recommended rule set

module.exports = {
    env: {
        es6: true,
    },
    extends: ["plugin:@darraghor/nestjs-typed/recommended"],
    parser: "@typescript-eslint/parser",
    parserOptions: {
        project: ["./tsconfig.json"],
        sourceType: "module",
        ecmaVersion: "es2019",
    },
    plugins: ["@darraghor/nestjs-typed"],
};

Note: the injectables test scans your whole project. It's best to filter out ts things that don't matter - use filterFromPaths configuration setting for this. There are some defaults already applied. See details below.

Note: You can easily turn off all the swagger rules if you don't use swagger by adding the no-swagger rule set AFTER the recommended rule set.

// all the other config
    extends: ["plugin:@darraghor/nestjs-typed/recommended",
    "plugin:@darraghor/nestjs-typed/no-swagger"
    ],
    // more config

Rules

Rule: provided-injected-should-match-factory-parameters

Checks that there are the same number of injected items in a Provider that are passed to the factory method

Passes (Myservide injected and myservice used in factory params)

export const MyOtherInjectableProvider: NotAProvider = {
    provide: MyOtherInjectable,
    useFactory: async (config: MyService): Promise<MyOtherInjectable> => {
        return new MyOtherInjectable();
    },
    inject: [MyService],
};

Fails (SecondService is not used in the factory)

export const MyOtherInjectableProvider: Provider = {
    provide: MyOtherInjectable,
    useFactory: async (config: MyService): Promise<MyOtherInjectable> => {
        return new MyOtherInjectable();
    },
    inject: [MyService, SecondService],
};

Rule: injectable-should-be-provided

Checks that a class marked with @Injectable is injected somewhere or used in a provider.

Fails if a thing marked as @Injectable is not in the providers of a module or provides in a provider.

There is some additional configuration you can provide for this rule. This is the default setting. You should overrride this with your src directory and any strings to filter out from paths (note that the filterFromPaths are NOT globs - just matched strings).

    "@darraghor/nestjs-typed/injectable-should-be-provided": [
            "error",
            {
                src: ["src/**/*.ts"],
                filterFromPaths: ["node_modules", ".test.", ".spec."],
            },
        ],

Rule: api-property-matches-property-optionality

This checks that you have added the correct api property decorator for your swagger documents.

There are specific decorators for optional properties and using the correct one affects Open Api generation.

The following FAILS because this is an optional property and should have @ApiPropertyOptional

class TestClass {
    @Expose()
    @ApiProperty()
    thisIsAStringProp?: string;
}

The following FAILS because this is a required property and should have @ApiProperty

class TestClass {
    @Expose()
    @ApiPropertyOptional()
    thisIsAStringProp!: string;
}

Rule: controllers-should-supply-api-tags

If you have more than a handful of api methods the swagger UI is difficult to navigate. It's easier to group api methods by using tags.

This PASSES because it has api tags

@ApiTags("my-group-of-methods")
@Controller("my-controller")
class TestClass {}

The following FAILS because it's missing api tags

@Controller("my-controller")
class TestClass {}

Rule: api-method-should-specify-api-operation

If you have an api method like @Get() you should specify the return status code (and type!) by using @ApiOkResponse and the other expected responses. I often leave out 400s and 500s because it's kind of assumed but they should be used if the return type changes!

This PASSES

class TestClass {
    @Get()
    @ApiOkResponse({type: String, isArray: true})
    @ApiBadRequestResponse({description: "Bad Request"})
    public getAll(): Promise<string[]> {
        return [];
    }
}

The following FAILS because it's missing api operation decorators

class TestClass {
    @Get()
    public getAll(): Promise<string[]> {
        return [];
    }
}