Webpack Mock Server

ExpressJs Middleware for webpack-dev-server with built-in hot-replacement (HMR) and typescript compiler. Uses for mocking api responses

Features

• Typescript support (>=v2.7): supports .js, .ts, .json files
• ES6 export/import support
• Hot replacement support
• Does not require proxy-path-pattern (because this is middleware that pipes routes to splitted server without proxy-path-pattern)
• Can be used without webpack (because this is expressjs middleware)
• Shows every configured response in user-friendly index.html (just click on mock-server-url in console after as mockServer is started)

Installing

Using npm (installing Typescript is required even if you don't use ts files):

npm i --save-dev webpack-mock-server typescript @types/express

Examples

Usage with defaults

// webpack.config.js - ver 5+
const webpackMockServer = require("webpack-mock-server");

module.exports = {
  devServer: {
    setupMiddlewares: (middlewares, devServer) => {
      webpackMockServer.use(devServer.app, {
         port: (devServer.options.port || 8080) + 1,
      });
      return middlewares;
    },
  },
};

// webpack.mock.ts - feel free to mock responses yourself
import webpackMockServer from "webpack-mock-server";
import nodePath from "path";

// app is express application
export default webpackMockServer.add((app, helper) => {
  // you can find more about express here: https://expressjs.com/
  app.get("/testGet", (_req, res) => {
    res.json("JS get-object can be here. Random int:" + helper.getRandomInt());
  });
  app.post("/testPost", (_req, res) => {
    res.json("JS post-object can be here");
  });

  // you can return any file easy. Example for json response from file:
  app.get("/testResponseFromJsonFile", (_req, res) => {
    res.sendFile(nodePath.join(__dirname, "./response.json"));
  });
});

// multiple exports are supported
export const result = webpackMockServer.add((app, helper) => {
  app.delete("/testDelete", (_req, res) => {
    res.json(
      "JS delete-object can be here. Random int:" + helper.getRandomInt()
    );
  });
  app.put("/testPut", (_req, res) => {
    res.json("JS put-object can be here");
  });
});

Usage with multiple/custom entries (instead of default webpack.mock.ts)

// webpack.config.js
const webpackMockServer = require("webpack-mock-server");

module.exports = {
  devServer: {
   setupMiddlewares: (middlewares, devServer) => {
        webpackMockServer.use(devServer.app, { // MockServerOptions here
          entry: [ // exact fileNames are expected (no wildcard or folder - use custom tsConfig instead)
              "api/users.mock.ts",
              "api/goods.mock.js"
          ],
          before: (req, res, next) => { // you can use this for custom-logging instead of logResponses: true, logRequests: true
              console.log(`Got request: ${req.method} ${req.url}`);
              res.once("finish", () => {
                 console.log(`Sent response: ${req.method} ${req.url}`);
               })
              next();
          }
      });
      return middlewares;
    }
  }
}

// api/users.mock.ts
... // take the example for ts-file above

// api/goods.mock.js
export default webpackMockServer.add((app, helper) => {
  app.get("/testGetGoods", (_req, res) => {
    res.json([{
        id: helper.getRandomInt(1, 999),
        name: "pen"
    }]);
  });
})

Usage with multiple entries by pattern (wildcard)

// webpack.config.js
const webpackMockServer = require("webpack-mock-server");

// for webpack v5
module.exports = {
  devServer: {
    setupMiddlewares: (middlewares, devServer) => {
      webpackMockServer.use(devServer.app, {
          /* set an empty-array or null to [entry], so entry will be defined
              from 'files' and 'includes' sections in [tsConfigFileName] */
          entry: [],
          tsConfigFileName: "mock/tsconfig.json" // use a different tsconfig-file that is contained entries
      });
      return middlewares;
    }
  }
}

// for webpack v4
module.exports = {
  devServer: {
    before: app =>
      webpackMockServer.use(app, {
          /* set an empty-array or null to [entry], so entry will be defined
              from 'files' and 'includes' sections in [tsConfigFileName]
          */
          entry: [],
          tsConfigFileName: "mock/tsconfig.json" // use a different tsconfig-file that is contained entries
      })
  }
}


// ./mock/tsconfig.json
{
  /*
   *  this is ordinary tsconfig file that overrides every option from [extends] - main tsconfig-file
   */
  "extends": "../tsconfig.json", // you can point the main tsconfig file or remove that property if it's not required
  "include": [  // wildcard-pattern is supported
      "../mock/*",
      "*.mock.ts",
      "**/global.d.ts",
  ],
  "files": [], // beside 'include' option you can point exact files here
  "exclude": ["*test.mock.ts"] // note: exclude option can override 'include' and 'files' options
}

Usage without webpack

As Express middleware: http://expressjs.com/en/guide/using-middleware.html

// webpack.config.js
const webpackMockServer = require("webpack-mock-server");

const express = require('express');
const app = express();

webpackMockServer.use(app, {/*mockServerOptions*/})
...
app.listen(1782);

// webpack.mock.ts - example you can find above
...

Usage with the whole default config

for webpack v5+

// webpack.config.js
...
const webpackMockServer = require("webpack-mock-server");

module.exports = {
  devServer: {
    setupMiddlewares: (middlewares, devServer) => { // it's different for webpack v4
      webpackMockServer.use(devServer.app, {
          port: (devServer.options.port || 8080) + 1, // app searches for free port (starts searching from pointed)
          verbose: false, // send info via console.log
          logRequests: false,
          logResponses: false,
          before: undefined, //can be used for logging
          entry: ["webpack.mock.ts"],
          tsConfigFileName: "tsconfig.json",
          compilerOptions: { // typescript.CompilerOptions that override tsconfig.json:[compilerOptions]
              strictNullChecks: false,
              noImplicitAny: false,
              noUnusedLocals: false,
              noUnusedParameters: false,
              skipLibCheck: true,
              resolveJsonModule: true,
          },
          strictCompilerOptions: { // these options impossible to override
              outDir: "" // used the following: {os.tmpdir()}/webpack-mock-server/{new Date().getTime()}
              rootDir: process.cwd(),
              noEmit: false,
              noEmitHelpers: false,
              esModuleInterop: true,
              module: ts.ModuleKind.CommonJS,
              declaration: false,
              moduleResolution: ModuleResolutionKind.Node10,
              target: defineTarget() // it defines target-ES based on NODE version
          }
      });
      return middlewares;
    }
  }
}

// webpack.mock.ts - example you can find above
...

for webpack v4

// webpack.config.js
...
const webpackMockServer = require("webpack-mock-server");

module.exports = {
  devServer: {
    before: app => // it's different for webpack v5
      webpackMockServer.use(app, {
          port: 8081, // app searches for free port (starts searching from pointed)
          verbose: false, // send info via console.log
          logRequests: false,
          logResponses: false,
          before: undefined, //can be used for logging
          entry: ["webpack.mock.ts"],
          tsConfigFileName: "tsconfig.json",
          compilerOptions: { // typescript.CompilerOptions that override tsconfig.json:[compilerOptions]
              strictNullChecks: false,
              noImplicitAny: false,
              noUnusedLocals: false,
              noUnusedParameters: false,
              skipLibCheck: true,
              resolveJsonModule: true
          },
          strictCompilerOptions: { // these options impossible to override
              outDir: "" // used the following: {os.tmpdir()}/webpack-mock-server/{new Date().getTime()}
              rootDir: process.cwd(),
              noEmit: false,
              noEmitHelpers: false,
              esModuleInterop: true,
              module: ts.ModuleKind.CommonJS,
              declaration: false,
              moduleResolution: ModuleResolutionKind.Node10,
              target: defineTarget() // it defines target-ES based on NODE version
          }
      })
  }
}

// webpack.mock.ts - example you can find above
...

Options

Note: Every path-file-name in options has to be pointed relative to the currentWorkingDirectory (process.cwd() in NodeJs) or point an absolute path

Param	Type	Default	Description
entry	String, String[], null	["webpack.mock.ts"]	Entry points for typescript-compiler (exact fileNames are expected). Set an empty array or null for using files, include and exlcude sections from tsConfigFileName. Otherwise these sections are ignored!
port	Number	8079	App searches for free port (starts searching from pointed)
verbose	Boolean	false	Show debug info in NodeJs via console.log
logResponses	Boolean	false	Show responses-info in NodeJs via console.log
logRequests	Boolean	false	Show request-info in NodeJs via console.log
before	(req, res, next) => void	undefined	Execute custom middleware prior to all other middleware internally within the server Can be used for custom-logging. Example here
compilerOptions	typescript.CompilerOptions	...	See the latest example above
strictCompilerOptions	typescript.CompilerOptions	...	readOnly. See the latest example above. These options impossible to override
tsConfigFileName	String	"tsconfig.json"	Pointer to typescript config file. Example here:

MockServerHelper. Methods

• .getRandomInt(min = 0, max = 2147483648) ⇒ Number - returns random integer between min and max
• .getUniqueIdInt() ⇒ Number - returns unique integer

Troubleshooting

• It's important to install Typescript even if use only JS-files (webpack-mock-server uses ts-compiler for gathering ts,js,json files)
• Don't use NodeJs require operator as dynamic to relative path. Use dirname in this case or absolute path (dirname is changed during the compilation)
• NodeJs caches every required module (file), so you maybe interested in clearing cache for require(.json)*. Use delete require.cache[require.resolve({yourPathName})] before you call require({yourPathName});
• Mockserver can't compile the TS-code. Possible reason: you have some extra import OR missed some global files (like global.d.ts). Solution: all mock-files must be without dependencies (imports) of components defined in the main-project files
  • If you have custom tsconfig.mock.json file check if all required \*d.ts files are included .. include: ["**/global.d.ts", ..] ..
  • To check what's wrong check compilation trace npx tsc --project tsconfig.mock.json --generateTrace traceDir OR enable logging via option verbose:true

// Wrong
app.get("/testResponseFromJsonFile", (_req, res) => {
  res.sendFile(require.resolve("./response.json"));
});

app.get("/testResponseFromJsonFile2", (_req, res) => {
  res.json(require("./response.json"));
});

// Correct
import nodePath from "path";

app.get("/testResponseFromJsonFile", (_req, res) => {
  res.sendFile(nodePath.join(__dirname, "./response.json"));
});

app.get("/testResponseFromJsonFile2", (_req, res) => {
  /* From NodeJs v8.9.0 you can use options: path
   * const resolvedPath = require.resolve("./response.json", { paths: [__dirname] });
   */
  const resolvedPath = require.resolve(
    nodePath.join(__dirname, "./response.json")
  );
  // removing NodeJS cache for getting the latest file
  delete require.cache[resolvedPath];
  res.json(require(resolvedPath));
});