feat(progess): emit progress-update

[hiroppy]

closes: #1666

• This is a bugfix
• This is a feature
• This is a code refactor
• This is a test update
• This is a docs update
• This is a metadata update

For Bugs and Features; did you add new tests?

yes

Motivation / Use-Case

Emit progress-update event.

Breaking Changes

no

Additional Info

[hiroppy]

fixed by eslint

[codecov]

Codecov Report

Merging #2498 into master will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #2498      +/-   ##
==========================================
+ Coverage   93.57%   93.58%   +0.01%     
==========================================
  Files          34       34              
  Lines        1322     1325       +3     
  Branches      380      381       +1     
==========================================
+ Hits         1237     1240       +3     
  Misses         83       83              
  Partials        2        2              

Impacted Files	Coverage Δ
lib/Server.js	96.78% <100.00%> (+0.01%)	⬆️
lib/servers/WebsocketServer.js	94.11% <100.00%> (+0.17%)	⬆️

---

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[alexander-akait]

Why we need check this.listeningApp? Is can be undefined?

[hiroppy]

We need this condition because this.setupProgressPlugin is called before this.createServer.

｡◕ˇ_ˇ◕｡ ~/p/w/webpack-dev-server (feature/emit-progress-update| 🎃 1 📦 1)  ᐅ npm run test:only -- progress-option

> webpack-dev-server@3.10.3 test:only /Users/hiroppy/programming/webpack/webpack-dev-server
> jest --forceExit "progress-option"

Test Suites: 1 failed, 1 total
Tests:       1 failed, 1 total
Snapshots:   0 total
Time:        3.755s
Ran all test suites matching /progress-option/i.
Force exiting Jest: Have you considered using `--detectOpenHandles` to detect async operations that kept running after all tests finished?
npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! webpack-dev-server@3.10.3 test:only: `jest --forceExit "progress-option"`
npm ERR! Exit status 1
npm ERR! 
npm ERR! Failed at the webpack-dev-server@3.10.3 test:only script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.

npm ERR! A complete log of this run can be found in:
npm ERR!     /Users/hiroppy/.npm/_logs/2020-04-03T10_59_27_800Z-debug.log
> npm run test:only -- progress-option

> webpack-dev-server@3.10.3 test:only /Users/hiroppy/programming/webpack/webpack-dev-server
> jest --forceExit "progress-option"

  console.info node_modules/webpack-log/src/loglevel/PrefixFactory.
js:55
    ℹ ｢wds｣: Project is running at http://localhost:8134/

  console.info node_modules/webpack-log/src/loglevel/PrefixFactory.js:55
    ℹ ｢wds｣: webpack output is served from undefined

  console.info node_modules/webpack-log/src/loglevel/PrefixFactory.js:55
    ℹ ｢wds｣: Content not from webpack is served from /Users/hiroppy/programming/webpack/webpack-dev-server

 PASS  test/server/progress-option.test.js
  progress
    output
      ✓ should show percentage progress without profile data (570ms
)

Test Suites: 1 passed, 1 total
Tests:       1 passed, 1 total
Snapshots:   0 total
Time:        2.107s
Ran all test suites matching /progress-option/i.
Force exiting Jest: Have you considered using `--detectOpenHandles` to detect async operations that kept running after all tests finished?

This log shows 2 situations that are added if or not.