packages: add initial codemods package

Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>

packages/codemods/src/index.ts

@@ -0,0 +1,75 @@
+/*
+ * Copyright 2020 Spotify AB
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import program, { Command } from 'commander';
+import chalk from 'chalk';
+import { version } from '../package.json';
+
+const codemods = [
+  {
+    name: 'core-imports',
+    description:
+      'Updates @backstage/core imports to use @backstage/core-* imports instead.',
+  },
+];
+
+function createCodemodAction(name: string) {
+  return (cmd: Command) => {
+    console.log(`Fake codemod ${cmd} ${name}`);
+  };
+}
+
+async function main(argv: string[]) {
+  program.name('backstage-codemods').version(version);
+
+  for (const codemod of codemods) {
+    program
+      .command(codemod.name)
+      .description(codemod.description)
+      .option('-d, --dry', 'Dry run, no changes written to files')
+      .action(createCodemodAction(codemod.name));
+  }
+
+  program.on('command:*', () => {
+    console.log();
+    console.log(chalk.red(`Invalid command: ${program.args.join(' ')}`));
+    console.log();
+    program.outputHelp();
+    process.exit(1);
+  });
+
+  program.parse(argv);
+}
+
+function exitWithError(err: Error & { code?: unknown }) {
+  process.stdout.write(`${err.name}: ${err.stack || err.message}\n`);
+
+  if (typeof err.code === 'number') {
+    process.exit(err.code);
+  } else {
+    process.exit(1);
+  }
+}
+
+process.on('unhandledRejection', (rejection: unknown) => {
+  if (rejection instanceof Error) {
+    exitWithError(rejection);
+  } else {
+    exitWithError(new Error(`Unknown rejection: '${rejection}'`));
+  }
+});
+
+main(process.argv).catch(exitWithError);