Allow using external templates in create-app

Signed-off-by: David Festal <dfestal@redhat.com>

.changeset/six-camels-perform.md

@@ -0,0 +1,5 @@
+---
+'@backstage/create-app': minor
+---
+
+Enable specifying an external application template when using the `create-app` CLI command.

packages/create-app/cli-report.md

@@ -11,5 +11,6 @@ Options:
   -V, --version
   --path [directory]
   --skip-install
+  --template-path [directory]
   -h, --help
 ```

packages/create-app/src/createApp.test.ts

@@ -20,6 +20,8 @@ import path from 'path';
 import { Command } from 'commander';
 import * as tasks from './lib/tasks';
 import createApp from './createApp';
+import { findPaths } from '@backstage/cli-common';
+import { tmpdir } from 'os';
 
 jest.mock('./lib/tasks');
 
@@ -74,6 +76,18 @@ describe('command entrypoint', () => {
     expect(createTemporaryAppFolderMock).toHaveBeenCalled();
     expect(tryInitGitRepositoryMock).toHaveBeenCalled();
     expect(templatingMock).toHaveBeenCalled();
+    expect(templatingMock.mock.lastCall?.[0]).toEqual(
+      findPaths(__dirname).resolveTarget(
+        'packages',
+        'create-app',
+        'src',
+        'templates',
+        'default-app',
+      ),
+    );
+    expect(templatingMock.mock.lastCall?.[1]).toEqual(
+      path.join(tmpdir(), 'MyApp'),
+    );
     expect(moveAppMock).toHaveBeenCalled();
     expect(buildAppMock).toHaveBeenCalled();
   });
@@ -84,6 +98,48 @@ describe('command entrypoint', () => {
     expect(checkPathExistsMock).toHaveBeenCalled();
     expect(tryInitGitRepositoryMock).toHaveBeenCalled();
     expect(templatingMock).toHaveBeenCalled();
+    expect(templatingMock.mock.lastCall?.[0]).toEqual(
+      findPaths(__dirname).resolveTarget(
+        'packages',
+        'create-app',
+        'src',
+        'templates',
+        'default-app',
+      ),
+    );
+    expect(templatingMock.mock.lastCall?.[1]).toEqual('myDirectory');
+    expect(buildAppMock).toHaveBeenCalled();
+  });
+
+  it('should call expected tasks with relative --template-path option', async () => {
+    const cmd = {
+      path: 'myDirectory',
+      templatePath: 'templateDirectory',
+    } as unknown as Command;
+    await createApp(cmd);
+    expect(checkPathExistsMock).toHaveBeenCalled();
+    expect(tryInitGitRepositoryMock).toHaveBeenCalled();
+    expect(templatingMock).toHaveBeenCalled();
+    expect(templatingMock.mock.lastCall?.[0]).toEqual(
+      findPaths(__dirname).resolveTarget('templateDirectory'),
+    );
+    expect(templatingMock.mock.lastCall?.[1]).toEqual('myDirectory');
+    expect(buildAppMock).toHaveBeenCalled();
+  });
+
+  it('should call expected tasks with absolute --template-path option', async () => {
+    const cmd = {
+      path: 'myDirectory',
+      templatePath: path.resolve('somewhere', 'templateDirectory'),
+    } as unknown as Command;
+    await createApp(cmd);
+    expect(checkPathExistsMock).toHaveBeenCalled();
+    expect(tryInitGitRepositoryMock).toHaveBeenCalled();
+    expect(templatingMock).toHaveBeenCalled();
+    expect(templatingMock.mock.lastCall?.[0]).toEqual(
+      path.resolve('somewhere', 'templateDirectory'),
+    );
+    expect(templatingMock.mock.lastCall?.[1]).toEqual('myDirectory');
     expect(buildAppMock).toHaveBeenCalled();
   });
 

packages/create-app/src/createApp.ts

@@ -65,7 +65,9 @@ export default async (opts: OptionValues): Promise<void> => {
     },
   ]);
 
-  const templateDir = paths.resolveOwn('templates/default-app');
+  const templateDir = opts.templatePath
+    ? resolvePath(paths.targetDir, opts.templatePath)
+    : paths.resolveOwn('templates/default-app');
   const tempDir = resolvePath(os.tmpdir(), answers.name);
 
   // Use `--path` argument as application directory when specified, otherwise
@@ -132,11 +134,15 @@ export default async (opts: OptionValues): Promise<void> => {
     if (!opts.skipInstall) {
       Task.log(
         `  Install the dependencies: ${chalk.cyan(
-          `cd ${answers.name} && yarn install`,
+          `cd ${opts.path ?? answers.name} && yarn install`,
         )}`,
       );
     }
-    Task.log(`  Run the app: ${chalk.cyan(`cd ${answers.name} && yarn dev`)}`);
+    Task.log(
+      `  Run the app: ${chalk.cyan(
+        `cd ${opts.path ?? answers.name} && yarn dev`,
+      )}`,
+    );
     Task.log(
       '  Set up the software catalog: https://backstage.io/docs/features/software-catalog/configuration',
     );

packages/create-app/src/index.ts

@@ -39,6 +39,10 @@ const main = (argv: string[]) => {
       '--skip-install',
       'Skip the install and builds steps after creating the app',
     )
+    .option(
+      '--template-path [directory]',
+      'Use an external application template instead of the default template',
+    )
     .action(cmd => createApp(cmd));
 
   program.parse(argv);