feat:

config/modules.js

@@ -0,0 +1,134 @@
+'use strict';
+
+const fs = require('fs');
+const path = require('path');
+const paths = require('./paths');
+const chalk = require('react-dev-utils/chalk');
+const resolve = require('resolve');
+
+/**
+ * Get additional module paths based on the baseUrl of a compilerOptions object.
+ *
+ * @param {Object} options
+ */
+function getAdditionalModulePaths(options = {}) {
+  const baseUrl = options.baseUrl;
+
+  if (!baseUrl) {
+    return '';
+  }
+
+  const baseUrlResolved = path.resolve(paths.appPath, baseUrl);
+
+  // We don't need to do anything if `baseUrl` is set to `node_modules`. This is
+  // the default behavior.
+  if (path.relative(paths.appNodeModules, baseUrlResolved) === '') {
+    return null;
+  }
+
+  // Allow the user set the `baseUrl` to `appSrc`.
+  if (path.relative(paths.appSrc, baseUrlResolved) === '') {
+    return [paths.appSrc];
+  }
+
+  // If the path is equal to the root directory we ignore it here.
+  // We don't want to allow importing from the root directly as source files are
+  // not transpiled outside of `src`. We do allow importing them with the
+  // absolute path (e.g. `src/Components/Button.js`) but we set that up with
+  // an alias.
+  if (path.relative(paths.appPath, baseUrlResolved) === '') {
+    return null;
+  }
+
+  // Otherwise, throw an error.
+  throw new Error(
+    chalk.red.bold(
+      "Your project's `baseUrl` can only be set to `src` or `node_modules`." +
+        ' Create React App does not support other values at this time.'
+    )
+  );
+}
+
+/**
+ * Get webpack aliases based on the baseUrl of a compilerOptions object.
+ *
+ * @param {*} options
+ */
+function getWebpackAliases(options = {}) {
+  const baseUrl = options.baseUrl;
+
+  if (!baseUrl) {
+    return {};
+  }
+
+  const baseUrlResolved = path.resolve(paths.appPath, baseUrl);
+
+  if (path.relative(paths.appPath, baseUrlResolved) === '') {
+    return {
+      src: paths.appSrc,
+    };
+  }
+}
+
+/**
+ * Get jest aliases based on the baseUrl of a compilerOptions object.
+ *
+ * @param {*} options
+ */
+function getJestAliases(options = {}) {
+  const baseUrl = options.baseUrl;
+
+  if (!baseUrl) {
+    return {};
+  }
+
+  const baseUrlResolved = path.resolve(paths.appPath, baseUrl);
+
+  if (path.relative(paths.appPath, baseUrlResolved) === '') {
+    return {
+      '^src/(.*)$': '<rootDir>/src/$1',
+    };
+  }
+}
+
+function getModules() {
+  // Check if TypeScript is setup
+  const hasTsConfig = fs.existsSync(paths.appTsConfig);
+  const hasJsConfig = fs.existsSync(paths.appJsConfig);
+
+  if (hasTsConfig && hasJsConfig) {
+    throw new Error(
+      'You have both a tsconfig.json and a jsconfig.json. If you are using TypeScript please remove your jsconfig.json file.'
+    );
+  }
+
+  let config;
+
+  // If there's a tsconfig.json we assume it's a
+  // TypeScript project and set up the config
+  // based on tsconfig.json
+  if (hasTsConfig) {
+    const ts = require(resolve.sync('typescript', {
+      basedir: paths.appNodeModules,
+    }));
+    config = ts.readConfigFile(paths.appTsConfig, ts.sys.readFile).config;
+    // Otherwise we'll check if there is jsconfig.json
+    // for non TS projects.
+  } else if (hasJsConfig) {
+    config = require(paths.appJsConfig);
+  }
+
+  config = config || {};
+  const options = config.compilerOptions || {};
+
+  const additionalModulePaths = getAdditionalModulePaths(options);
+
+  return {
+    additionalModulePaths: additionalModulePaths,
+    webpackAliases: getWebpackAliases(options),
+    jestAliases: getJestAliases(options),
+    hasTsConfig,
+  };
+}
+
+module.exports = getModules();