fix(cli-create): fix scoped creation (yarnpkg#6239)

* fix(cli-create): fix scoped creation

This one works as it should:
yarn create @scope/name => @scope/create-name

There were problems when name was omitted:

Before:
yarn create @scope => create-
yarn create @scope/ => @scope/create-

After:
yarn create @scope => @scope/create
yarn create @scope/ => @scope/create

Fixes yarnpkg#6233

* refactor(cli-create): make parsePackageName more robust and add tests

* refactor(cli-create): add missing typyings

__tests__/commands/create.js

@@ -0,0 +1,101 @@
+// @flow
+
+import {parsePackageName, coerceCreatePackageName} from '../../src/cli/commands/create';
+
+describe(`parsePackageName`, () => {
+  test('invalid', () => {
+    expect(() => {
+      parsePackageName('@/name');
+    }).toThrowError(`Scope should not be empty, got "@/name"`);
+    expect(() => {
+      parsePackageName('/name');
+    }).toThrowError(`Name should not start with "/", got "/name"`);
+    expect(() => {
+      parsePackageName('./name');
+    }).toThrowError(`Name should not start with ".", got "./name"`);
+  });
+
+  test('basic', () => {
+    expect(parsePackageName('name')).toEqual({
+      fullName: 'name',
+      name: 'name',
+      scope: '',
+      path: '',
+      full: 'name',
+    });
+    expect(parsePackageName('@scope/name')).toEqual({
+      fullName: '@scope/name',
+      name: 'name',
+      scope: '@scope',
+      path: '',
+      full: '@scope/name',
+    });
+    expect(parsePackageName('@scope/name/path/to/file.js')).toEqual({
+      fullName: '@scope/name',
+      name: 'name',
+      scope: '@scope',
+      path: 'path/to/file.js',
+      full: '@scope/name/path/to/file.js',
+    });
+  });
+
+  test('without name', () => {
+    expect(parsePackageName('@scope/')).toEqual({
+      fullName: '@scope',
+      name: '',
+      scope: '@scope',
+      path: '',
+      full: '@scope',
+    });
+    expect(parsePackageName('@scope')).toEqual({
+      fullName: '@scope',
+      name: '',
+      scope: '@scope',
+      path: '',
+      full: '@scope',
+    });
+  });
+});
+
+describe(`coerceCreatePackageName`, () => {
+  test('invalid', () => {
+    expect(() => {
+      coerceCreatePackageName('@/name');
+    }).toThrow();
+    expect(() => {
+      coerceCreatePackageName('/name');
+    }).toThrow();
+    expect(() => {
+      coerceCreatePackageName('./name');
+    }).toThrow();
+  });
+
+  test('basic', () => {
+    expect(coerceCreatePackageName('name')).toEqual({
+      fullName: 'create-name',
+      name: 'create-name',
+      scope: '',
+      path: '',
+      full: 'create-name',
+    });
+    expect(coerceCreatePackageName('@scope/name')).toEqual({
+      fullName: '@scope/create-name',
+      name: 'create-name',
+      scope: '@scope',
+      path: '',
+      full: '@scope/create-name',
+    });
+    expect(coerceCreatePackageName('@scope/name/path/to/file.js')).toEqual({
+      fullName: '@scope/create-name',
+      name: 'create-name',
+      scope: '@scope',
+      path: 'path/to/file.js',
+      full: '@scope/create-name/path/to/file.js',
+    });
+  });
+
+  test('not postfixing with "-" if name is emptu', () => {
+    expect(coerceCreatePackageName('@scope/').fullName).toEqual('@scope/create');
+    expect(coerceCreatePackageName('@scope').fullName).toEqual('@scope/create');
+  });
+});

src/cli/commands/create.js

@@ -16,17 +16,47 @@ export function hasWrapper(commander: Object, args: Array<string>): boolean {
   return true;
 }
 
+export function parsePackageName(str: string): Object {
+  if (str.charAt(0) === '/') {
+    throw new Error(`Name should not start with "/", got "${str}"`);
+  }
+  if (str.charAt(0) === '.') {
+    throw new Error(`Name should not start with ".", got "${str}"`);
+  }
+  const parts = str.split('/');
+  const isScoped = str.charAt(0) === '@';
+  if (isScoped && parts[0] === '@') {
+    throw new Error(`Scope should not be empty, got "${str}"`);
+  }
+  const scope = isScoped ? parts[0] : '';
+  const name = parts[isScoped ? 1 : 0] || '';
+  const path = parts.slice(isScoped ? 2 : 1).join('/');
+  const fullName = [scope, name].filter(Boolean).join('/');
+  const full = [scope, name, path].filter(Boolean).join('/');
+
+  return {fullName, name, scope, path, full};
+}
+
+export function coerceCreatePackageName(str: string): Object {
+  const pkgNameObj = parsePackageName(str);
+  const coercedName = pkgNameObj.name !== '' ? `create-${pkgNameObj.name}` : `create`;
+  const coercedPkgNameObj = {
+    ...pkgNameObj,
+    name: coercedName,
+    fullName: [pkgNameObj.scope, coercedName].filter(Boolean).join('/'),
+    full: [pkgNameObj.scope, coercedName, pkgNameObj.path].filter(Boolean).join('/'),
+  };
+  return coercedPkgNameObj;
+}
+
 export async function run(config: Config, reporter: Reporter, flags: Object, args: Array<string>): Promise<void> {
   const [builderName, ...rest] = args;
 
   if (!builderName) {
     throw new MessageError(reporter.lang('invalidPackageName'));
   }
 
-  const packageName = builderName.replace(/^(@[^\/]+\/)?/, '$1create-');
-  const packageDir = packageName.replace(/^(?:(@[^\/]+)\/)?.*/, '$1');
-  const commandName = packageName.replace(/^@[^\/]+\//, '');
-
+  const {fullName: packageName, scope: packageDir, name: commandName} = coerceCreatePackageName(builderName);
   await runGlobal(config, reporter, {}, ['add', packageName]);
 
   const binFolder = await getBinFolder(config, {});