Conditionally drop console messages from production build

Add a environment variable, `DROP_CONSOLE`, to specify if console
function calls should be dropped in the production build.

Author: candrews

docusaurus/docs/advanced-configuration.md

@@ -24,6 +24,7 @@ You can adjust various development and production settings by setting environmen
 | GENERATE_SOURCEMAP      | 🚫 Ignored  |  ✅ Used   | When set to `false`, source maps are not generated for a production build. This solves out of memory (OOM) issues on some smaller machines.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              |
 | INLINE_RUNTIME_CHUNK    | 🚫 Ignored  |  ✅ Used   | By default, Create React App will embed the runtime script into `index.html` during the production build. When set to `false`, the script will not be embedded and will be imported as usual. This is normally required when dealing with CSP.                                                                                                                                                                                                                                                                                                                                                                                                                           |
 | IMAGE_INLINE_SIZE_LIMIT | 🚫 Ignored  |  ✅ Used   | By default, images smaller than 10,000 bytes are encoded as a data URI in base64 and inlined in the CSS or JS build artifact. Set this to control the size limit in bytes. Setting it to 0 will disable the inlining of images.                                                                                                                                                                                                                                                                                                                                                                                                                                          |
+| DROP_CONSOLE    | 🚫 Ignored  |  ✅ Used   | When set to `true`, `console.*` functions during the production build will be dropped. When set to `false`, the default, these function calls will be included as usual.                                                                                                                                                                                                                                                                                                                                                                                                                           |
 | EXTEND_ESLINT           |   ✅ Used   |  ✅ Used   | When set to `true`, user provided ESLint configs will be used by `eslint-loader`. Note that any rules set to `"error"` will stop the application from building.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          |
 | FAST_REFRESH            |   ✅ Used   | 🚫 Ignored | When set to `true`, enables experimental support for fast refresh to allow you to tweak your components in real time without reloading the page.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         |
 | TSC_COMPILE_ON_ERROR    |   ✅ Used   |  ✅ Used   | When set to `true`, you can run and properly build TypeScript projects even if there are TypeScript type check errors. These errors are printed as warnings in the terminal and/or browser console.                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |

packages/react-scripts/config/webpack.config.js

@@ -57,6 +57,8 @@ const imageInlineSizeLimit = parseInt(
   process.env.IMAGE_INLINE_SIZE_LIMIT || '10000'
 );
 
+const shouldDropConsole = process.env.DROP_CONSOLE === 'true';
+
 // Check if TypeScript is setup
 const useTypeScript = fs.existsSync(paths.appTsConfig);
 
@@ -233,6 +235,7 @@ module.exports = function (webpackEnv) {
               ecma: 8,
             },
             compress: {
+              drop_console: shouldDropConsole,
               ecma: 5,
               warnings: false,
               // Disabled because of an issue with Uglify breaking seemingly valid code: