ng-swagger-gen: A Swagger 2.0 code generator for Angular

This project is a NPM module that generates model interfaces and web service clients from a Swagger 2.0 specification. The generated classes follow the principles of Angular.

Angular / RxJS version compatibility:

• Starting with version 1.0.0, Angular 6+ is required.
• Version 0.11.x supports Angular 4.3+ (with rxjs 5.5) and Angular 5.

Major version upgrade notices

• Angular 6 bundles RxJS 6, which changed the API, mostly imports. As such, starting with ng-swagger-gen version 1.0.0, both peer dependencies for @angular/core and rxjs have been upgraded. If you plan to stay in Angular 5, change the ng-swagger-gen version in package.json to ~0.11.0;
• Up to the version 0.8.x of this generator the deprecated Http Angular module was used to generating requests. Starting with version 0.9, HttpClient is used instead - hence the requirement for Angular 4.3+. Also, taking the opportunity to break backwards compatibility, some additional changes were also performed, such as returning Observables instead of Promises. For more details, please see the wiki page Upgrading from previous versions to 0.9.

Design principles

• It must be easy to use;
• It should provide access to the original response, so, for example, headers can be read. But also it should provide easy access to the result;
• It should generate code which follows the concepts of an Angular 4+ application, such as Modules, Injectables, etc;
• All the server communication is implemented using HttpClient;
• The generated model should handle correctly inheritance and enumerations. Starting from version 0.10 all modules are generated as TypeScript interfaces rather than classes, avoiding additional overhead on generated JavaScript;
• An Angular Module (@NgModule) is generated, which exports all services;
• One service is generated per Swagger tag;
• It should be possible to choose a subset of tags from which to generate services;
• It should generate only the models actually used by the generated services;
• The configuration of the root URL for the API is set globally in an @Injectable class called ApiConfiguration, but can also be set on each service, for increased flexibility.

Here are a few notes:

• Starting with version 0.11.0, the Swagger definition can be either a JSON or YAML file (thanks to @jfyne);
• Starting with version 0.11.0, file downloads / uploads are supported using the native Blob type;
• Each operation is assumed to have a single tag. If none is declared, a default of Api (configurable) is assumed. If multiple tags are declared, the first one is used;
• Each tag generates a service class;
• Operations that don't declare an id have an id generated. However, it is recommended that all operations define an id;
• Two methods are generated for each service operation: one returning Observable<HttpResponse<T>> (the method is suffixed with Response) and another one returning Observable<T>;
• This generator may not cover all corner cases of the Swagger 2.0 specification;
• OpenAPI 3.0 is not supported, but may be added in the future;
• Probably many more.

Requirements

The generator itself has very few requirements, basically json-schema-ref-parser, argparse and mustache.

However, starting with the version 1.0.0, the generated code requires both Angular 6.0+ and RxJS 6.0+. These versions are expressed as peerDependencies, so make sure you don't have unmet peer dependencies. If you are stuck on previous versions of Angular / RxJS, you can use ng-swagger-gen version as ~0.11.0, which supports Angular 4.3, and RxJS 5.5.

How to use it

In your project, run:

cd <your_angular_app_dir>
npm install ng-swagger-gen --save-dev
node_modules/.bin/ng-swagger-gen -i <path_to_swagger_json> [-o output_dir]

Where:

• path_to_swagger_json is either a relative path to the Swagger JSON file or an URL.
• output_dir is the directory where the generated code will be outputted. It is recommended that this directory is ignored on GIT (or whatever source control software you are using), for example, by adding its name to .gitignore. The default output directory if nothing is specified is src/app/api.

Please, run the ng-swagger-gen with the --help argument to view all available command line arguments.

Generated folder structure

The folder src/app/api (or your custom folder) will contain the following structure:

project_root
+- src
   +- app
      +- api
         +- models
         |  +- model1.ts
         |  +- model1.example.json
         |  +- ...
         |  +- modeln.ts
         |  +- modeln.example.json
         +- services
         |  +- tag1.service.ts
         |  +- ...
         |  +- tagn.service.ts
         +- api.module.ts
         +- api-configuration.ts
         +- base-service.ts
         +- models.ts
         +- services.ts

The files are:

• api/models/modeln.ts: One file per model file is generated here. Enumerations are also correctly generated;
• api/models/modeln.ts: One file per example is generated for each model that has example section.
• api/models.ts: An index script which exports all model interfaces. It is used to make it easier for application classes to import models, so they can use import { Model1, Model2 } from 'api/models' instead of import { Model1 } from 'api/models/model1' and import { Model2 } from 'api/models/model2';
• api/services/tagn.service.ts: One file per Swagger tag is generated here;
• api/services.ts: An index script which exports all service classes, similar to the analog file for models;
• api/api-configuration.ts: An @Injectable class that holds global configuration. Currently the only global configuration option is rootUrl, which defaults to the URL in the source Swagger definition, and can be overridden in your application before doing the first API call;
• api/base-service.ts: Base class which all generated services extend. It provides the ability to override the root URL used by a particular service. If the service root URL is null, which is the default, the service will use the global root URL defined in ApiConfiguration;
• api/api.module.ts: A module that declares an NgModule that provides all services, plus the ApiConfiguration instance. Your root application module should import this module to ensure all services are available via dependency injection on your application.

Using a configuration file

On regular usage it is recommended to use a configuration file instead of passing command-line arguments to ng-swagger-gen. The default configuration file name is ng-swagger-gen.json, and should be placed on the root folder of your NodeJS project. Besides allowing to omit the command-line arguments, using a the configuration file allows a greater degree of control over the generation.

An accompanying JSON schema is also available, so the configuration file can be validated, and IDEs can autocomplete the file. If you have installed and saved the ng-swagger-gen module in your node project, you can use a local copy of the JSON schema on ./node_modules/ng-swagger-gen/ng-swagger-gen-schema.json. It is also possible to use the online version at https://github.com/cyclosproject/ng-swagger-gen/blob/master/ng-swagger-gen-schema.json.

It is also possible to specify the configuration file to use. This is useful when multiple APIs are generated. To specify a configuration file, use the argument --config or its short form, -c, like this:

ng-swagger-gen --config custom-config.json

Generating the configuration file

To generate a configuration file, run the following in the root folder of your project;

ng-swagger-gen --gen-config [-i path_to_swagger_json] [-o output_dir]

This will generate the ng-swagger-gen.json file in the current directory with the property defaults, plus the input Swagger JSON path (or URL) and the output directory that were specified together. Both are optional, and the file is generated anyway.

Configuration file reference

The supported properties in the JSON file are:

• swagger: The location of the swagger descriptor in JSON format. May be either a local file or URL.
• output: Where generated files will be written to. Defaults to src/app/api.
• includeTags: When specified, filters the generated services, including only those corresponding to this list of tags.
• excludeTags: When specified, filters the generated services, excluding any service corresponding to this list of tags.
• ignoreUnusedModels: Indicates whether or not to ignore model files that are not referenced by any operation. Defaults to true.
• minParamsForContainer: Indicates the minimum number of parameters to wrap operation parameters in a container class. Defaults to 2.
• defaultTag: The assumed tag for operations that don't define any. Defaults to Api.
• removeStaleFiles: Indicates whether or not to remove any files in the output folder that were not generated by ng-swagger-gen. Defaults to true.
• modelIndex: Indicates whether or not to generate the file which exports all models. Defaults to true.
• serviceIndex: Indicates whether or not to generate the file which exports all services. Defaults to true.
• apiModule: Indicates whether or not to generate the Angular module which provides all services and the ApiConfiguration. Defaults to true.
• enumModule: Indicates whether or not to export an additional TypeScript module (not to be confused with Angular's @NgModule) for each enum model, exporting values as constants and providing the values() method. Setting to false will reduce the size of the generated code. Defaults to true.
• templates: Path to override the Mustache templates used to generate files.
• generateExamples: When set to true, ng-swagger-gen will extract the example from the example section of each definition and add put it to the respective *.example.json files right besides the model files.

Configuration file example

The following is an example of a configuration file which will choose a few tags to generate, and chose not to generate the ApiModule class:

{
  "$schema": "./node_modules/ng-swagger-gen/ng-swagger-gen-schema.json",
  "swagger": "my-swagger.json",
  "includeTags": [
    "Blogs",
    "Comments",
    "Users"
  ],
  "apiModule": false
}

This will generate only the services for the chosen tags, and also skip the generation of any interfaces for models which are not used by any of the generated services.

Setting up a node script

Regardless If your Angular project was generated or is managed by Angular CLI, or you have started your project with some other seed (for example, using webpack directly), you can setup a script to make sure the generated API classes are consistent with the swagger descriptor.

To do so, create the ng-swagger-gen.json configuration file and add the following scripts to your package.json:

{
  "scripts": {
    "start": "ng-swagger-gen && ng serve",
    "build": "ng-swagger-gen && ng build -prod"
  }
}

This way whenever you run npm start or npm run build, the API classes will be generated before actually serving / building your application.

Also, if you use several configuration files, you can specify multiple times the call to ng-swagger-gen, like:

{
  "scripts": {
    "start": "ng-swagger-gen -c api1.json && ng-swagger-gen -c api2.json && ng serve",
    "build": "ng-swagger-gen -c api1.json && ng-swagger-gen -c api2.json && ng build -prod"
  }
}

Specifying the root URL / web service endpoint

The easiest way to specify a custom root URL (web service endpoint URL) is to inject the ApiConfiguration instance in some service and set the rootUrl property from there.

Alternatively, define a provider for APP_INITIALIZER in your root module, like this:

export function initApiConfiguration(config: ApiConfiguration): Function {
  return () => {
    config.rootUrl = 'https://some-root-url.com';
  };
}
export const INIT_API_CONFIGURATION: Provider = {
  provide: APP_INITIALIZER,
  useFactory: initApiConfiguration,
  deps: [ApiConfiguration],
  multi: true
};

/**
 * Then declare the provider. In this example, the AppModule is also
 * importing the ApiModule, which is important to get access to the
 * generated services
 */
@NgModule({
  declarations: [
    AppComponent
  ],
  imports: [
    ApiModule
  ],
  providers: [
    INIT_API_CONFIGURATION
  ],
  bootstrap: [
    AppComponent
  ]
})
export class AppModule { }

Passing request headers / customizing the request

To pass request headers, such as authorization or API keys, as well as having a centralized error handling, a standard HttpInterceptor should be used. It is basically an @Injectable that is called before each request, and can customize both requests and responses.

Here is an example:

@Injectable()
export class ApiInterceptor implements HttpInterceptor {
  intercept(req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
    // Apply the headers
    req = req.clone({
      setHeaders: {
        'ApiToken': '234567890'
      }
    });

    // Also handle errors globally
    return next.handle(req).pipe(
      tap(x => x, err => {
        // Handle this err
        console.error(`Error performing request, status code = ${err.status}`);
      })
    );
  }
}

Then, both the HttpInterceptor implementation and the injection token HTTP_INTERCEPTORS pointing to it must be provided in your application module, like this:

import { NgModule, Provider, forwardRef } from '@angular/core';
import { HTTP_INTERCEPTORS } from '@angular/common/http';

import { ApiInterceptor } from './api.interceptor';

export const API_INTERCEPTOR_PROVIDER: Provider = {
  provide: HTTP_INTERCEPTORS,
  useExisting: forwardRef(() => ApiInterceptor),
  multi: true
};

@NgModule({
  providers: [
    ApiInterceptor,
    API_INTERCEPTOR_PROVIDER
  ]
})
export class AppModule {}

Finer control over specific requests can also be achieved, such as:

• Set the immediate next request to use a BASIC authentication for login, and the subsequent ones to use a session key in another request header;
• Set the next request to not use the default error handling, and handle errors directly in the calling code.

To do so, just create another shared @Injectable(), for example, called ApiRequestConfiguration, which has state for such special cases. Then inject it on both the HttpInterceptor and in the client code that makes requests. Here is an example for such class for controlling the authentication:

import { Injectable } from '@angular/core';
import { HttpRequest } from '@angular/common/http';

/**
 * Configuration for the performed HTTP requests
 */
@Injectable()
export class ApiRequestConfiguration {
  private nextAuthHeader: string;
  private nextAuthValue: string;

  /** Set to basic authentication */
  basic(user: string, password: string): void {
    this.nextAuthHeader = 'Authorization';
    this.nextAuthValue = 'Basic ' + btoa(user + ':' + password);
  }

  /** Set to session key */
  nextAsSession(sessionKey: string): void {
    this.nextAuthHeader = 'Session';
    this.nextAuthValue = sessionKey;
  }

  /** Clear any authentication headers (to be called after logout) */
  clear(): void {
    this.nextAuthHeader = null;
    this.nextAuthValue = null;
  }

  /** Apply the current authorization headers to the given request */
  apply(req: HttpRequest<any>): HttpRequest<any> {
    const headers = {};
    if (this.nextAuthHeader) {
      headers[this.nextAuthHeader] = this.nextAuthValue;
    }
    // Apply the headers to the request
    return req.clone({
      setHeaders: headers
    });
  }
}

Then change the ApiInterceptor class to call the apply method. And, of course, add ApiRequestConfiguration to your module providers and inject it on your components or services.

Swagger extensions

The swagger specification doesn't allow referencing an enumeration to be used as an operation parameter. Hence, ng-swagger-gen supports the vendor extension x-type in operations, whose value could either be a model name representing an enumeration or Array<EnumName> or List<EnumName> (both are equivalents) to use an array of models.

Who uses this project

This project was developed by the Cyclos development team, and, in fact, the Cyclos REST API is the primary test case for generated classes.

That doesn't mean that the generator works only for the Cyclos API. For instance, the following commands will generate an API client for Swagger's PetStore example, assuming Angular CLI is installed:

ng new petstore
cd petstore
npm install --save-dev ng-swagger-gen
node_modules/.bin/ng-swagger-gen -i http://petstore.swagger.io/v2/swagger.json