[DEVTOOLS-283] Allow regeneration based on yo config file

Author: mrclay

README.md

@@ -181,6 +181,24 @@ OPTIONS
 
 _See code: [src/commands/new.ts](https://github.com/forumone/forumone-cli/blob/v1.5.0/src/commands/new.ts)_
 
+## `f1 regen CONFIG TARGET`
+
+Regenerate a new project from an existing .yo-rc.json file.
+
+```
+USAGE
+  $ f1 regen CONFIG TARGET
+
+ARGUMENTS
+  CONFIG  path of .yo-rc.json file or project directory
+  TARGET  directory name to create
+
+OPTIONS
+  -h, --help  show CLI help
+  --dry-run   print command instead of running
+  --next      use prerelease generator for testing
+```
+
 ## `f1 run SERVICE`
 
 run an arbitrary compose service

src/commands/regen.ts

@@ -0,0 +1,99 @@
+import Command, { flags } from '@oclif/command';
+import fs from 'fs';
+import path from 'path';
+import validFilename from 'valid-filename';
+
+import recreateProject from '../project/recreateProject';
+
+
+function mkdirDryRun(target: string) {
+  const relative = path.relative(process.cwd(), target);
+  process.stdout.write(`mkdir ${relative}\n`);
+}
+
+function findConfigFile(filePath: string): string {
+  if (!fs.existsSync(filePath)) {
+    throw new Error(`Path '${filePath}' does not exist.`);
+  }
+
+  if (fs.statSync(filePath).isDirectory()) {
+    return findConfigFile(path.join(filePath, '.yo-rc.json'));
+  }
+
+  if (!fs.statSync(filePath).isFile()) {
+    throw new Error(`Path '${filePath}' is not a file.`);
+  }
+
+  return filePath;
+}
+
+export default class Regen extends Command {
+  static description = 'Regenerate a new project from an existing .yo-rc.json file.';
+
+  static flags = {
+    help: flags.help({ char: 'h' }),
+    'dry-run': flags.boolean({
+      description: 'print command instead of running',
+    }),
+    next: flags.boolean({
+      description: 'use prerelease generator for testing',
+    }),
+  };
+
+  static args = [
+    {
+      name: 'config',
+      description: 'path of .yo-rc.json file or project directory',
+      required: true,
+    },
+    {
+      name: 'target',
+      description: 'directory name to create',
+      required: true,
+    },
+  ];
+
+  async run() {
+    const { args, flags } = this.parse(Regen);
+
+    if (!validFilename(args.target)) {
+      return this.error(`Argument '${args.target}' is not a valid filename.`, {
+        exit: 1,
+      });
+    }
+
+    const directory = path.join(process.cwd(), args.target);
+    const configPath = path.join(process.cwd(), args.config);
+
+    let configFile;
+    try {
+      configFile = findConfigFile(configPath);
+    } catch (e) {
+      return this.error(e.getMessage(), {
+        exit: 1,
+      });
+    }
+
+    try {
+      const createDirectory = flags['dry-run'] ? mkdirDryRun : fs.mkdirSync;
+      createDirectory(directory);
+    } catch (error) {
+      if (error.code === 'EEXIST') {
+        return this.error(
+          `Failed to create '${args.target}' because it already exists.`,
+          { exit: 1 },
+        );
+      }
+
+      return this.error(error, { exit: 1 });
+    }
+
+    const command = recreateProject({
+      configFile,
+      directory,
+      next: flags.next,
+    });
+
+    return flags['dry-run'] ? command.dryRun() : command.run();
+  }
+}

src/project/recreateProject.ts

@@ -0,0 +1,25 @@
+import runNpx from '../process/runNpx';
+
+export interface RecreateProjectOptions {
+  configFile: string;
+  directory: string;
+  next: boolean;
+}
+
+// Use `npx' to ensure that users always have the latest generator version.
+function recreateProject({ configFile, directory, next }: RecreateProjectOptions) {
+  const tagSuffix = next ? '@next' : '';
+
+  // yo-gen-run --name web-starter --config ./tmp-wp/.yo-rc.json --out ./tmp-wp2
+  return runNpx([
+    'yo-gen-run',
+    '--name', 'web-starter',
+    '--config', configFile,
+    '--out', directory,
+  ], {
+    cwd: directory,
+    packages: ['yo', 'yeoman-gen-run', 'generator-web-starter' + tagSuffix],
+  });
+}
+
+export default recreateProject;