Revert "Update postcss packages" (#10216)

This reverts commit 580ed5d.

Author: ianschmitz

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

@@ -125,25 +125,23 @@ module.exports = function (webpackEnv) {
         // package.json
         loader: require.resolve('postcss-loader'),
         options: {
-          postcssOptions: {
-            plugins: [
-              require('postcss-flexbugs-fixes'),
-              [
-                require('postcss-preset-env'),
-                {
-                  autoprefixer: {
-                    flexbox: 'no-2009',
-                  },
-                  stage: 3,
-                },
-              ],
-              // Adds PostCSS Normalize as the reset css with default options,
-              // so that it honors browserslist config in package.json
-              // which in turn let's users customize the target behavior as per their needs.
-              postcssNormalize(),
-            ],
-          },
-          sourceMap: isEnvProduction && shouldUseSourceMap,
+          // Necessary for external CSS imports to work
+          // https://github.com/facebook/create-react-app/issues/2677
+          ident: 'postcss',
+          plugins: () => [
+            require('postcss-flexbugs-fixes'),
+            require('postcss-preset-env')({
+              autoprefixer: {
+                flexbox: 'no-2009',
+              },
+              stage: 3,
+            }),
+            // Adds PostCSS Normalize as the reset css with default options,
+            // so that it honors browserslist config in package.json
+            // which in turn let's users customize the target behavior as per their needs.
+            postcssNormalize(),
+          ],
+          sourceMap: isEnvProduction ? shouldUseSourceMap : isEnvDevelopment,
         },
       },
     ].filter(Boolean);

packages/react-scripts/package.json

@@ -65,10 +65,9 @@
     "mini-css-extract-plugin": "0.11.3",
     "optimize-css-assets-webpack-plugin": "5.0.4",
     "pnp-webpack-plugin": "1.6.4",
-    "postcss": "8.1.14",
-    "postcss-flexbugs-fixes": "5.0.2",
-    "postcss-loader": "4.1.0",
-    "postcss-normalize": "9.0.0",
+    "postcss-flexbugs-fixes": "4.2.1",
+    "postcss-loader": "3.0.0",
+    "postcss-normalize": "8.0.1",
     "postcss-preset-env": "6.7.0",
     "postcss-safe-parser": "5.0.2",
     "prompts": "2.4.0",