删除 Vue JS 中的元素时在 dev 中工作但在 prod 中不工作时的动画

Question

使用 CSS-transitions，我有一个组件，该组件在值发生变化时具有动画。

当我使用npm run dev 运行此程序时，整个过程运行良好，如下所示：

但是，当使用 npm run build 并将代码投入 Nginx 服务器上的生产时，动画不起作用并且元素很快被移除：

是什么导致了 dev 和 prod 之间的这种差异？有没有更好的方法来获得这个动画效果？

BugRepro.vue，我用它来重现这个错误：

<template>
  <div class="bugrepro">
    <div class="empty-space"></div>
    <Value :value="someNumber"></Value>
    <button @click="change()">Change it!</button>
  </div>
</template>
<script>
import Value from "./Value"

export default {
  name: "BugRepro",
  data() {
    return {
      someNumber: 20
    };
  },
  components :{
      Value
  },
  methods: {
    change() {
      this.someNumber += 1;
    }
  }
};
</script>
<style>
.empty-space {
  margin-top: 100px;
}
</style>

Value.vue，它保存数字并负责在值变化时处理动画：

<template>
  <div class="card-property">
    <button class="btn btn-sm active fa" :class="`btn-info fa-tint`" style="cursor:default" title="Mana Cost">
      {{ value }}
    </button>
    <transition-group name="diff-once" class="pos-absolute" tag="div" @after-enter="removeDiff()">
      <button v-for="diff in diffs" :key="diff.id"
        class="btn btn-sm active fa diff-once" :class="`btn-info fa-tint`" style="cursor:default">
        {{diff.value}}
      </button>
    </transition-group>
  </div>
</template>
<script>
export default {
  name: "Value",
  props: ["value"],
  data() {
    return {
      diffs: [],
      diffId: 0
    };
  },
  methods: {
    removeDiff() {
      this.diffs.splice(0, 1);
    }
  },
  watch: {
    value: function(newValue, oldValue) {
      console.log(typeof newValue);
      let diff = newValue - oldValue;
      this.diffs.push({value: diff, id: this.diffId});
      this.diffId++;
    }
  }
}
</script>
<style>
.card-property {
    position: relative;
}

.diff-once-leave-active {
  transition: all 1s;
  position: absolute;
}

.pos-absolute {
  position: absolute;
  top: 0;
  left: 0;
}

.diff-once-leave {
  opacity: 1;
}

.diff-once-leave-to {
  opacity: 0;
  transform: translateY(-30px);
}
</style>

我认为问题可能出在我的 webpack.prod.conf 中，我已经尝试禁用 OptimizeCSSPlugin，但没有帮助：

'use strict'
const path = require('path')
const utils = require('./utils')
const webpack = require('webpack')
const config = require('../config')
const merge = require('webpack-merge')
const baseWebpackConfig = require('./webpack.base.conf')
const CopyWebpackPlugin = require('copy-webpack-plugin')
const HtmlWebpackPlugin = require('html-webpack-plugin')
const ExtractTextPlugin = require('extract-text-webpack-plugin')
const OptimizeCSSPlugin = require('optimize-css-assets-webpack-plugin')
const UglifyJsPlugin = require('uglifyjs-webpack-plugin')

const env = process.env.NODE_ENV === 'testing'
  ? require('../config/test.env')
  : require('../config/prod.env')

const webpackConfig = merge(baseWebpackConfig, {
  module: {
    rules: utils.styleLoaders({
      sourceMap: config.build.productionSourceMap,
      extract: true,
      usePostCSS: true
    })
  },
  devtool: config.build.productionSourceMap ? config.build.devtool : false,
  output: {
    path: config.build.assetsRoot,
    filename: utils.assetsPath('js/[name].[chunkhash].js'),
    chunkFilename: utils.assetsPath('js/[id].[chunkhash].js')
  },
  plugins: [
    // http://vuejs.github.io/vue-loader/en/workflow/production.html
    new webpack.DefinePlugin({
      'process.env': env
    }),
    new UglifyJsPlugin({
      uglifyOptions: {
        compress: {
          warnings: false
        }
      },
      sourceMap: config.build.productionSourceMap,
      parallel: true
    }),
    // extract css into its own file
    new ExtractTextPlugin({
      filename: utils.assetsPath('css/[name].[contenthash].css'),
      // Setting the following option to `false` will not extract CSS from codesplit chunks.
      // Their CSS will instead be inserted dynamically with style-loader when the codesplit chunk has been loaded by webpack.
      // It's currently set to `true` because we are seeing that sourcemaps are included in the codesplit bundle as well when it's `false`, 
      // increasing file size: https://github.com/vuejs-templates/webpack/issues/1110
      allChunks: true,
    }),
    // Compress extracted CSS. We are using this plugin so that possible
    // duplicated CSS from different components can be deduped.
    new OptimizeCSSPlugin({
      cssProcessorOptions: config.build.productionSourceMap
        ? { safe: true, map: { inline: false } }
        : { safe: true }
    }),
    // generate dist index.html with correct asset hash for caching.
    // you can customize output by editing /index.html
    // see https://github.com/ampedandwired/html-webpack-plugin
    new HtmlWebpackPlugin({
      filename: process.env.NODE_ENV === 'testing'
        ? 'index.html'
        : config.build.index,
      template: 'index.html',
      inject: true,
      minify: {
        removeComments: true,
        collapseWhitespace: true,
        removeAttributeQuotes: true
        // more options:
        // https://github.com/kangax/html-minifier#options-quick-reference
      },
      // necessary to consistently work with multiple chunks via CommonsChunkPlugin
      chunksSortMode: 'dependency'
    }),
    // keep module.id stable when vendor modules does not change
    new webpack.HashedModuleIdsPlugin(),
    // enable scope hoisting
    new webpack.optimize.ModuleConcatenationPlugin(),
    // split vendor js into its own file
    new webpack.optimize.CommonsChunkPlugin({
      name: 'vendor',
      minChunks (module) {
        // any required modules inside node_modules are extracted to vendor
        return (
          module.resource &&
          /\.js$/.test(module.resource) &&
          module.resource.indexOf(
            path.join(__dirname, '../node_modules')
          ) === 0
        )
      }
    }),
    // extract webpack runtime and module manifest to its own file in order to
    // prevent vendor hash from being updated whenever app bundle is updated
    new webpack.optimize.CommonsChunkPlugin({
      name: 'manifest',
      minChunks: Infinity
    }),
    // This instance extracts shared chunks from code splitted chunks and bundles them
    // in a separate chunk, similar to the vendor chunk
    // see: https://webpack.js.org/plugins/commons-chunk-plugin/#extra-async-commons-chunk
    new webpack.optimize.CommonsChunkPlugin({
      name: 'app',
      async: 'vendor-async',
      children: true,
      minChunks: 3
    }),

    // copy custom static assets
    new CopyWebpackPlugin([
      {
        from: path.resolve(__dirname, '../static'),
        to: config.build.assetsSubDirectory,
        ignore: ['.*']
      }
    ])
  ]
})

if (config.build.productionGzip) {
  const CompressionWebpackPlugin = require('compression-webpack-plugin')

  webpackConfig.plugins.push(
    new CompressionWebpackPlugin({
      asset: '[path].gz[query]',
      algorithm: 'gzip',
      test: new RegExp(
        '\\.(' +
        config.build.productionGzipExtensions.join('|') +
        ')$'
      ),
      threshold: 10240,
      minRatio: 0.8
    })
  )
}

if (config.build.bundleAnalyzerReport) {
  const BundleAnalyzerPlugin = require('webpack-bundle-analyzer').BundleAnalyzerPlugin
  webpackConfig.plugins.push(new BundleAnalyzerPlugin())
}

module.exports = webpackConfig

由于我不知道哪些文件是相关的，you can also find all files on github

最简单的重现步骤：

• 检查源代码，运行npm install 和npm run dev
• 转到http://localhost:42637 并单击按钮 - 动画正常工作
• 停止开发服务器并运行npm run build
• 在某些 HTTP 服务器上托管文件，例如 Nginx
• 转到托管文件的 HTTP 服务器并单击按钮 - 动画不工作

一旦我知道哪些文件最相关，我当然会将它们添加到这篇文章中。

Answer 1

问题在于，一旦您编译到生产环境中，来自 Bootstrap 的所有 CSS 文件和您的组件都会合并为一个，并通过一些 CSS 优化运行。这会导致您的 CSS 样式在多个点定义过渡。有你的.diff-once-... 样式，还有你的.btn 样式。在 DEV 模式下，.diff-once-... 在级联中更高，在生产中，它是.btn。因此按钮中的转换规则会覆盖您稍后定义的所有规则。您可以通过提高动画类的特异性来解决这个问题，例如

.btn.diff-once-leave-to { ... }
.btn.diff-once-leave { ... }

或者（推荐）通过添加作用域样式。这样，所有动画样式默认情况下都会获得更高的特异性，并且不会干扰您应用中的任何其他样式：

<style scoped>
.card-property {
    position: relative;
}

.diff-once-leave-active {
  transition: all 1s;
  position: absolute;
}

.pos-absolute {
  position: absolute;
  top: 0;
  left: 0;
}

.diff-once-leave {
  opacity: 1;
}

.diff-once-leave-to {
  opacity: 0;
  transform: translateY(-30px);
}
</style>

希望这会有所帮助！