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));
});