remove babel-plugin-preval and generate errormap as a build step

.gitignore

@@ -2,4 +2,5 @@ node_modules
 dist
 .DS_Store
 *.log
-package-lock.json
+package-lock.json
+**/styled-components/src/utils/errors.js

babel-preset.js

@@ -6,18 +6,15 @@ module.exports = () => ({
     [
       '@babel/preset-env',
       {
-        targets: NODE_ENV === 'test'
-          ? { node: 'current' }
-          : undefined,
+        targets: NODE_ENV === 'test' ? { node: 'current' } : undefined,
         loose: true,
         modules,
       },
     ],
     '@babel/preset-react',
-    '@babel/preset-flow'
+    '@babel/preset-flow',
   ],
   plugins: [
-    'babel-plugin-preval',
     ['babel-plugin-transform-react-remove-prop-types', { mode: 'unsafe-wrap' }],
     ['@babel/plugin-proposal-object-rest-spread', { loose: true }],
     ['@babel/plugin-proposal-class-properties', { loose: true }],

packages/styled-components/package.json

@@ -12,12 +12,14 @@
   },
   "sideEffects": false,
   "scripts": {
+    "generateErrors": "node scripts/generateErrorMap.js",
+    "prebuild": "rimraf dist && npm run generateErrors",
     "build": "rollup -c",
-    "prebuild": "rimraf dist",
     "postbuild": "npm run lint:size",
     "flow": "flow check",
     "flow:watch": "flow-watch",
-    "test": "run-s test:*",
+    "pretest": "npm run generateErrors",
+    "test": "npm run test:web && npm run test:native && npm run test:primitives",
     "test:web": "jest -c ../../scripts/jest/config.main.js",
     "test:native": "jest -c ../../scripts/jest/config.native.js",
     "test:primitives": "jest -c ../../scripts/jest/config.primitives.js",

packages/styled-components/scripts/generateErrorMap.js

@@ -0,0 +1,22 @@
+const fs = require('fs');
+const path = require('path');
+
+const md = fs.readFileSync(path.join(__dirname, '../src/utils/errors.md'), 'utf8');
+
+const errorMap = md
+  .split(/^#/gm)
+  .slice(1)
+  .reduce((errors, str) => {
+    const [, code, message] = str.split(/^.*?(\d+)\s*\n/);
+
+    // eslint-disable-next-line no-param-reassign
+    errors[code] = message;
+
+    return errors;
+  }, {});
+
+fs.writeFileSync(
+  path.join(__dirname, '../src/utils/errors.js'),
+  `export default ${JSON.stringify(errorMap)};`,
+  'utf8'
+);

packages/styled-components/src/utils/error.js

@@ -1,24 +1,7 @@
 // @flow
+import errorMap from './errors';
 
-declare var preval: Function;
-
-/**
- * Parse errors.md and turn it into a simple hash of code: message
- */
-const ERRORS =
-  process.env.NODE_ENV !== 'production'
-    ? preval`
-      const fs = require('fs');
-      const md = fs.readFileSync(__dirname + '/errors.md', 'utf8');
-
-      module.exports = md.split(/^#/gm).slice(1).reduce((errors, str) => {
-        const [, code, message] = str.split(/^.*?(\\d+)\\s*\\n/)
-        errors[code] = message
-
-        return errors;
-      }, {});
-    `
-    : {};
+const ERRORS = process.env.NODE_ENV !== 'production' ? errorMap : {};
 
 /**
  * super basic version of sprintf