fix(importer): handle the case where productName doesn't exist

`yarn init` and `npm init` don't add a `productName` to `package.json`, and when running import on a project without a `productName`, the config setup would throw an exception, so guard against that. This also implements a very basic import unit test -- maybe we want more, but this at least covers this bug fix and other sanity-check-level issues.

src/util/forge-config.js

@@ -42,9 +42,11 @@ const proxify = (object, envPrefix) => {
  * Sets sensible defaults for the `config.forge` object.
  */
 export function setInitialForgeConfig(packageJSON) {
+  const { name = '', productName = '' } = packageJSON;
+
   /* eslint-disable no-param-reassign */
-  packageJSON.config.forge.electronWinstallerConfig.name = packageJSON.name.replace(/-/g, '_');
-  packageJSON.config.forge.windowsStoreConfig.name = packageJSON.productName.replace(/-/g, '');
+  packageJSON.config.forge.electronWinstallerConfig.name = name.replace(/-/g, '_');
+  packageJSON.config.forge.windowsStoreConfig.name = productName.replace(/-/g, '');
   packageJSON.config.forge.electronPackagerConfig.packageManager = yarnOrNpm();
   /* eslint-enable no-param-reassign */
 }

test/slow/api_spec_slow.js

@@ -12,12 +12,13 @@ import installDeps from '../../src/util/install-dependencies';
 import readPackageJSON from '../../src/util/read-package-json';
 import yarnOrNpm from '../../src/util/yarn-or-npm';
 
-const installer = process.argv.find(arg => arg.startsWith('--installer=')) || `--installer=${yarnOrNpm()}`;
+const installerArg = process.argv.find(arg => arg.startsWith('--installer=')) || `--installer=${yarnOrNpm()}`;
+const installer = installerArg.substr(12);
 const forge = proxyquire.noCallThru().load('../../src/api', {
   './install': async () => {},
 });
 
-describe(`electron-forge API (with installer=${installer.substr(12)})`, () => {
+describe(`electron-forge API (with installer=${installer})`, () => {
   let dir;
   let dirID = Date.now();
 
@@ -156,6 +157,20 @@ describe(`electron-forge API (with installer=${installer.substr(12)})`, () => {
     });
   });
 
+  describe('import', () => {
+    before(async () => {
+      await ensureTestDirIsNonexistent();
+      await fs.mkdir(dir);
+      execSync(`${installer} init -y`, {
+        cwd: dir,
+      });
+    });
+
+    it('works', async () => {
+      await forge.import({ dir });
+    });
+  });
+
   describe('after init', () => {
     before(async () => {
       dir = path.resolve(os.tmpdir(), `electron-forge-test-${dirID}/electron-forge-test`);