"vue-cli-service build --watch" on production mode does not remove some old build files

[JudgedPluto]

Version

4.5.9

Environment info

System:
    OS: Windows 10 10.0.19041
    CPU: (4) x64 Intel(R) Core(TM) i7-7500U CPU @ 2.70GHz
Binaries:
    Node: 12.18.3 - E:\NodeJS\node.EXE
    Yarn: Not Found
    npm: 6.14.6 - E:\NodeJS\npm.CMD
Browsers:
    Chrome: Not Found
    Edge: Spartan (44.19041.1.0), Chromium (87.0.664.66)
npmPackages:
    @vue/babel-helper-vue-jsx-merge-props:  1.2.1
    @vue/babel-helper-vue-transform-on:  1.0.0-rc.2
    @vue/babel-plugin-jsx:  1.0.0-rc.5
    @vue/babel-plugin-transform-vue-jsx:  1.2.1
    @vue/babel-preset-app:  4.5.9
    @vue/babel-preset-jsx:  1.2.4
    @vue/babel-sugar-composition-api-inject-h:  1.2.1
    @vue/babel-sugar-composition-api-render-instance:  1.2.4
    @vue/babel-sugar-functional-vue:  1.2.2
    @vue/babel-sugar-inject-h:  1.2.2
    @vue/babel-sugar-v-model:  1.2.3
    @vue/babel-sugar-v-on:  1.2.3
    @vue/cli-overlay:  4.5.9
    @vue/cli-plugin-babel: ~4.5.0 => 4.5.9
    @vue/cli-plugin-eslint: ~4.5.0 => 4.5.9
    @vue/cli-plugin-router:  4.5.9
    @vue/cli-plugin-vuex:  4.5.9
    @vue/cli-service: ~4.5.0 => 4.5.9
    @vue/cli-shared-utils:  4.5.9
    @vue/compiler-core:  3.0.4
    @vue/compiler-dom:  3.0.4
    @vue/compiler-sfc: ^3.0.0 => 3.0.4
    @vue/compiler-ssr:  3.0.4
    @vue/component-compiler-utils:  3.2.0
    @vue/preload-webpack-plugin:  1.1.2
    @vue/reactivity:  3.0.4
    @vue/runtime-core:  3.0.4
    @vue/runtime-dom:  3.0.4
    @vue/shared:  3.0.4
    @vue/web-component-wrapper:  1.2.0
    eslint-plugin-vue: ^7.0.0-0 => 7.3.0
    vue: ^3.0.0 => 3.0.4
    vue-eslint-parser:  7.3.0
    vue-hot-reload-api:  2.3.4
    vue-loader:  15.9.6 (16.1.2)
    vue-style-loader:  4.1.2
    vue-template-es2015-compiler:  1.9.1
npmGlobalPackages:
    @vue/cli: Not Found

Steps to reproduce

1. Create a Vue 3 Project: vue create app-name
2. Build the project: vue-cli-service build --mode production --watch
3. Modify the project code and save.

What is expected?

Old build files must be removed and new build files will be added.

What is actually happening?

Although the files are rebuilt and added to the build folder, some old build files are not removed from the build folder.

---

Some notes to add:

1. Adding --watch option will always switch to development mode, so --mode option will be needed for production build.
2. Here are the list of files generated from a sample project, before and after modifying the project code: dir /s /b

Before:

E:\Vue3\app-bug\dist\css
E:\Vue3\app-bug\dist\favicon.ico
E:\Vue3\app-bug\dist\img
E:\Vue3\app-bug\dist\index.html
E:\Vue3\app-bug\dist\js
E:\Vue3\app-bug\dist\css\app.fb0c6e1c.css
E:\Vue3\app-bug\dist\img\logo.82b9c7a5.png
E:\Vue3\app-bug\dist\js\app.26359725.js
E:\Vue3\app-bug\dist\js\app.26359725.js.map
E:\Vue3\app-bug\dist\js\chunk-vendors.530cb5a2.js
E:\Vue3\app-bug\dist\js\chunk-vendors.530cb5a2.js.map

After:

E:\Vue3\app-bug\dist\css
E:\Vue3\app-bug\dist\favicon.ico
E:\Vue3\app-bug\dist\img
E:\Vue3\app-bug\dist\index.html
E:\Vue3\app-bug\dist\js
E:\Vue3\app-bug\dist\css\app.fb0c6e1c.css
E:\Vue3\app-bug\dist\img\logo.82b9c7a5.png
E:\Vue3\app-bug\dist\js\app.26359725.js
E:\Vue3\app-bug\dist\js\app.26359725.js.map
E:\Vue3\app-bug\dist\js\app.d740d19f.js
E:\Vue3\app-bug\dist\js\app.d740d19f.js.map
E:\Vue3\app-bug\dist\js\chunk-vendors.530cb5a2.js
E:\Vue3\app-bug\dist\js\chunk-vendors.530cb5a2.js.map