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app_vue/node_modules/@vue/cli-service/lib/config/terserOptions.js

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+// @ts-check
+const TerserPlugin = require('terser-webpack-plugin')
+
+const genTerserOptions = (defaultOptions, options) => {
+  const userOptions = options.terser && options.terser.terserOptions
+  // user's config is first
+  return {
+    ...defaultOptions,
+    ...userOptions
+  }
+}
+
+const terserMinify = (options) => ({
+  terserOptions: genTerserOptions(
+    {
+      compress: {
+        // turn off flags with small gains to speed up minification
+        arrows: false,
+        collapse_vars: false, // 0.3kb
+        comparisons: false,
+        computed_props: false,
+        hoist_funs: false,
+        hoist_props: false,
+        hoist_vars: false,
+        inline: false,
+        loops: false,
+        negate_iife: false,
+        properties: false,
+        reduce_funcs: false,
+        reduce_vars: false,
+        switches: false,
+        toplevel: false,
+        typeofs: false,
+
+        // a few flags with noticeable gains/speed ratio
+        // numbers based on out of the box vendor bundle
+        booleans: true, // 0.7kb
+        if_return: true, // 0.4kb
+        sequences: true, // 0.7kb
+        unused: true, // 2.3kb
+
+        // required features to drop conditional branches
+        conditionals: true,
+        dead_code: true,
+        evaluate: true
+      },
+      mangle: {
+        safari10: true
+      }
+    },
+    options
+  ),
+  parallel: options.parallel,
+  extractComments: false
+})
+
+// `terserOptions` options will be passed to `esbuild`
+// Link to options - https://esbuild.github.io/api/#minify
+const esbuildMinify = (options) => ({
+  minify: TerserPlugin.esbuildMinify,
+  terserOptions: genTerserOptions(
+    {
+      minify: false,
+      minifyWhitespace: true,
+      minifyIdentifiers: false,
+      minifySyntax: true
+    },
+    options
+  ),
+  parallel: options.parallel
+})
+
+// `terserOptions` options will be passed to `swc` (`@swc/core`)
+// Link to options - https://swc.rs/docs/config-js-minify
+const swcMinify = (options) => ({
+  minify: TerserPlugin.swcMinify,
+  terserOptions: genTerserOptions(
+    {
+      compress: {
+        unused: true
+      },
+      mangle: true
+    },
+    options
+  ),
+  parallel: options.parallel
+})
+
+// `terserOptions` options will be passed to `uglify-js`
+// Link to options - https://github.com/mishoo/UglifyJS#minify-options
+const uglifyJsMinify = (options) => ({
+  minify: TerserPlugin.uglifyJsMinify,
+  terserOptions: genTerserOptions({}, options),
+  parallel: options.parallel
+})
+
+// Currently we do not allow custom minify function
+const getMinify = (options) => {
+  const { minify = 'terser' } = options.terser || {}
+
+  const minifyMap = {
+    terser: terserMinify,
+    esbuild: esbuildMinify,
+    swc: swcMinify,
+    uglifyJs: uglifyJsMinify
+  }
+  return minifyMap[minify](options)
+}
+
+module.exports = getMinify