Modify Generated Files

Read and modify files in the generated project directory. Plugins have full filesystem access.

Basic File Operations

Read a File

plugin.ts

import { StartPluginWithLambda, type CyanPluginInput, type PluginOutput } from '@atomicloud/cyan-sdk';
import * as fs from 'fs/promises';
import * as path from 'path';

StartPluginWithLambda(async (input: CyanPluginInput): Promise<PluginOutput> => {
  const { directory } = input;

  // Read file
  const readmePath = path.join(directory, 'README.md');
  const content = await fs.readFile(readmePath, 'utf-8');

  console.log('README content:', content);

  return { directory };
});

plugin.py

from cyan_sdk import start_plugin_with_fn, CyanPluginInput, PluginOutput
import os

@start_plugin_with_fn
async def main(input: CyanPluginInput) -> PluginOutput:
    directory = input.directory

    # Read file
    readme_path = os.path.join(directory, 'README.md')
    with open(readme_path, 'r', encoding='utf-8') as f:
        content = f.read()

    print(f'README content: {content}')

    return {'directory': directory}

Plugin.cs

using CyanSdk;
using System.IO;

[PluginMain]
public static class Plugin
{
    public static async Task<PluginOutput> Main(CyanPluginInput input)
    {
        var directory = input.Directory;

        // Read file
        var readmePath = Path.Combine(directory, "README.md");
        var content = await File.ReadAllTextAsync(readmePath);

        Console.WriteLine($"README content: {content}");

        return new PluginOutput { Directory = directory };
    }
}

Write a File

plugin.ts

StartPluginWithLambda(async (input) => {
  const { directory } = input;

  const readmePath = path.join(directory, 'README.md');
  await fs.writeFile(readmePath, '# My Project\n\nGenerated by CyanPrint');

  return { directory };
});

plugin.py

@start_plugin_with_fn
async def main(input: CyanPluginInput) -> PluginOutput:
    directory = input.directory

    readme_path = os.path.join(directory, 'README.md')
    with open(readme_path, 'w', encoding='utf-8') as f:
        f.write('# My Project\n\nGenerated by CyanPrint')

    return {'directory': directory}

Plugin.cs

[PluginMain]
public static async Task<PluginOutput> Main(CyanPluginInput input)
{
    var directory = input.Directory;

    var readmePath = Path.Combine(directory, "README.md");
    await File.WriteAllTextAsync(readmePath, "# My Project\n\nGenerated by CyanPrint");

    return new PluginOutput { Directory = directory };
}

Modify a File

plugin.ts

StartPluginWithLambda(async (input) => {
  const { directory } = input;

  const readmePath = path.join(directory, 'README.md');

  // Read
  let content = await fs.readFile(readmePath, 'utf-8');

  // Modify
  content = content + '\n\n## Generated\n\nThis project was generated by CyanPrint.';

  // Write back
  await fs.writeFile(readmePath, content);

  return { directory };
});

plugin.py

@start_plugin_with_fn
async def main(input: CyanPluginInput) -> PluginOutput:
    directory = input.directory

    readme_path = os.path.join(directory, 'README.md')

    # Read
    with open(readme_path, 'r', encoding='utf-8') as f:
        content = f.read()

    # Modify
    content = content + '\n\n## Generated\n\nThis project was generated by CyanPrint.'

    # Write back
    with open(readme_path, 'w', encoding='utf-8') as f:
        f.write(content)

    return {'directory': directory}

Plugin.cs

[PluginMain]
public static async Task<PluginOutput> Main(CyanPluginInput input)
{
    var directory = input.Directory;

    var readmePath = Path.Combine(directory, "README.md");

    // Read
    var content = await File.ReadAllTextAsync(readmePath);

    // Modify
    content += "\n\n## Generated\n\nThis project was generated by CyanPrint.";

    // Write back
    await File.WriteAllTextAsync(readmePath, content);

    return new PluginOutput { Directory = directory };
}

Common Patterns

Update JSON File

plugin.ts

StartPluginWithLambda(async (input) => {
  const { directory } = input;

  // Read package.json
  const pkgPath = path.join(directory, 'package.json');
  const pkg = JSON.parse(await fs.readFile(pkgPath, 'utf-8'));

  // Modify
  pkg.scripts = pkg.scripts || {};
  pkg.scripts.dev = 'next dev --turbo';
  pkg.scripts.build = 'next build';

  // Add dependencies
  pkg.dependencies = pkg.dependencies || {};
  pkg.dependencies['lodash'] = '^4.17.21';

  // Write back
  await fs.writeFile(pkgPath, JSON.stringify(pkg, null, 2));

  return { directory };
});

plugin.py

import json

@start_plugin_with_fn
async def main(input: CyanPluginInput) -> PluginOutput:
    directory = input.directory

    # Read package.json
    pkg_path = os.path.join(directory, 'package.json')
    with open(pkg_path, 'r', encoding='utf-8') as f:
        pkg = json.load(f)

    # Modify
    pkg.setdefault('scripts', {})
    pkg['scripts']['dev'] = 'next dev --turbo'
    pkg['scripts']['build'] = 'next build'

    # Add dependencies
    pkg.setdefault('dependencies', {})
    pkg['dependencies']['lodash'] = '^4.17.21'

    # Write back
    with open(pkg_path, 'w', encoding='utf-8') as f:
        json.dump(pkg, f, indent=2)

    return {'directory': directory}

Plugin.cs

using System.Text.Json;

[PluginMain]
public static async Task<PluginOutput> Main(CyanPluginInput input)
{
    var directory = input.Directory;

    // Read package.json
    var pkgPath = Path.Combine(directory, "package.json");
    var jsonContent = await File.ReadAllTextAsync(pkgPath);
    var pkg = JsonSerializer.Deserialize<Dictionary<string, object>>(jsonContent);

    // Modify
    var scripts = new Dictionary<string, string>
    {
        ["dev"] = "next dev --turbo",
        ["build"] = "next build"
    };
    pkg["scripts"] = scripts;

    // Add dependencies
    var dependencies = new Dictionary<string, string>
    {
        ["lodash"] = "^4.17.21"
    };
    pkg["dependencies"] = dependencies;

    // Write back
    var options = new JsonSerializerOptions { WriteIndented = true };
    await File.WriteAllTextAsync(pkgPath, JsonSerializer.Serialize(pkg, options));

    return new PluginOutput { Directory = directory };
}

Add to Existing File

plugin.ts

StartPluginWithLambda(async (input) => {
  const { directory, config } = input;
  const cfg = config as { author?: string };

  const readmePath = path.join(directory, 'README.md');

  // Check if file exists
  try {
    let content = await fs.readFile(readmePath, 'utf-8');

    // Add author line if provided
    if (cfg.author) {
      content = content.replace(
        '# ',
        `# Project\n\nAuthor: ${cfg.author}\n\n`
      );
      await fs.writeFile(readmePath, content);
    }
  } catch {
    // File doesn't exist, create it
    await fs.writeFile(readmePath, `# Project\n\nAuthor: ${cfg.author || 'Unknown'}\n`);
  }

  return { directory };
});

plugin.py

@start_plugin_with_fn
async def main(input: CyanPluginInput) -> PluginOutput:
    directory = input.directory
    cfg = input.config or {}
    author = cfg.get('author')

    readme_path = os.path.join(directory, 'README.md')

    # Check if file exists
    try:
        with open(readme_path, 'r', encoding='utf-8') as f:
            content = f.read()

        # Add author line if provided
        if author:
            content = content.replace(
                '# ',
                f'# Project\n\nAuthor: {author}\n\n'
            )
            with open(readme_path, 'w', encoding='utf-8') as f:
                f.write(content)
    except FileNotFoundError:
        # File doesn't exist, create it
        with open(readme_path, 'w', encoding='utf-8') as f:
            f.write(f'# Project\n\nAuthor: {author or "Unknown"}\n')

    return {'directory': directory}

Plugin.cs

[PluginMain]
public static async Task<PluginOutput> Main(CyanPluginInput input)
{
    var directory = input.Directory;
    var cfg = input.Config as Dictionary<string, object>;
    var author = cfg?.GetValueOrDefault("author")?.ToString();

    var readmePath = Path.Combine(directory, "README.md");

    // Check if file exists
    try
    {
        var content = await File.ReadAllTextAsync(readmePath);

        // Add author line if provided
        if (author != null)
        {
            content = content.Replace(
                "# ",
                $"# Project\n\nAuthor: {author}\n\n"
            );
            await File.WriteAllTextAsync(readmePath, content);
        }
    }
    catch (FileNotFoundException)
    {
        // File doesn't exist, create it
        await File.WriteAllTextAsync(readmePath, $"# Project\n\nAuthor: {author ?? "Unknown"}\n");
    }

    return new PluginOutput { Directory = directory };
}

Create New Files

.gitignore

.env.example

plugin.ts

StartPluginWithLambda(async (input) => {
  const { directory } = input;

  // Create .gitignore
  await fs.writeFile(
    path.join(directory, '.gitignore'),
    `node_modules/
dist/
.env
*.log
`
  );

  // Create .env.example
  await fs.writeFile(
    path.join(directory, '.env.example'),
    `DATABASE_URL=postgres://localhost:5432/mydb
API_KEY=your-api-key
`
  );

  // Create directory and file
  const githubDir = path.join(directory, '.github', 'workflows');

  await fs.mkdir(githubDir, { recursive: true });

  await fs.writeFile(
    path.join(githubDir, 'ci.yml'),
    `name: CI
on: [push, pull_request]
jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - run: npm ci
      - run: npm test
`
  );

  return { directory };
});

plugin.py

@start_plugin_with_fn
async def main(input: CyanPluginInput) -> PluginOutput:
    directory = input.directory

    # Create .gitignore
    with open(os.path.join(directory, '.gitignore'), 'w', encoding='utf-8') as f:
        f.write('''node_modules/
dist/
.env
*.log
''')

    # Create .env.example
    with open(os.path.join(directory, '.env.example'), 'w', encoding='utf-8') as f:
        f.write('''DATABASE_URL=postgres://localhost:5432/mydb
API_KEY=your-api-key
''')

    # Create directory and file
    github_dir = os.path.join(directory, '.github', 'workflows')
    os.makedirs(github_dir, exist_ok=True)

    with open(os.path.join(github_dir, 'ci.yml'), 'w', encoding='utf-8') as f:
        f.write('''name: CI
on: [push, pull_request]
jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - run: npm ci
      - run: npm test
''')

    return {'directory': directory}

Plugin.cs

[PluginMain]
public static async Task<PluginOutput> Main(CyanPluginInput input)
{
    var directory = input.Directory;

    // Create .gitignore
    await File.WriteAllTextAsync(
        Path.Combine(directory, ".gitignore"),
        @"node_modules/
dist/
.env
*.log
"
    );

    // Create .env.example
    await File.WriteAllTextAsync(
        Path.Combine(directory, ".env.example"),
        @"DATABASE_URL=postgres://localhost:5432/mydb
API_KEY=your-api-key
"
    );

    // Create directory and file
    var githubDir = Path.Combine(directory, ".github", "workflows");
    Directory.CreateDirectory(githubDir);

    await File.WriteAllTextAsync(
        Path.Combine(githubDir, "ci.yml"),
        @"name: CI
on: [push, pull_request]
jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - run: npm ci
      - run: npm test
"
    );

    return new PluginOutput { Directory = directory };
}

Delete Files

plugin.ts

StartPluginWithLambda(async (input) => {
  const { directory } = input;

  // Delete specific files
  const filesToDelete = [
    'CONTRIBUTING.md',
    'LICENSE',
    '.github/FUNDING.yml'
  ];

  for (const file of filesToDelete) {
    const filePath = path.join(directory, file);
    try {
      await fs.unlink(filePath);
    } catch {
      // File doesn't exist, ignore
    }
  }

  return { directory };
});

plugin.py

@start_plugin_with_fn
async def main(input: CyanPluginInput) -> PluginOutput:
    directory = input.directory

    # Delete specific files
    files_to_delete = [
        'CONTRIBUTING.md',
        'LICENSE',
        '.github/FUNDING.yml'
    ]

    for file in files_to_delete:
        file_path = os.path.join(directory, file)
        try:
            os.remove(file_path)
        except FileNotFoundError:
            # File doesn't exist, ignore
            pass

    return {'directory': directory}

Plugin.cs

[PluginMain]
public static async Task<PluginOutput> Main(CyanPluginInput input)
{
    var directory = input.Directory;

    // Delete specific files
    var filesToDelete = new[]
    {
        "CONTRIBUTING.md",
        "LICENSE",
        ".github/FUNDING.yml"
    };

    foreach (var file in filesToDelete)
    {
        var filePath = Path.Combine(directory, file);
        try
        {
            File.Delete(filePath);
        }
        catch (FileNotFoundException)
        {
            // File doesn't exist, ignore
        }
    }

    return new PluginOutput { Directory = directory };
}

Using Glob Patterns

Process multiple files matching a pattern using the glob npm package:

npm install glob

yarn add glob

pnpm add glob

plugin.ts

import { glob } from 'glob';

StartPluginWithLambda(async (input) => {
  const { directory } = input;

  // Find all markdown files
  const mdFiles = await glob('**/*.md', { cwd: directory });

  for (const file of mdFiles) {
    const filePath = path.join(directory, file);
    let content = await fs.readFile(filePath, 'utf-8');

    // Add frontmatter if missing
    if (!content.startsWith('---')) {
      content = `---
title: ${path.basename(file, '.md')}
---

${content}`;
      await fs.writeFile(filePath, content);
    }
  }

  return { directory };
});

plugin.py

import glob as glob_module

@start_plugin_with_fn
async def main(input: CyanPluginInput) -> PluginOutput:
    directory = input.directory

    # Find all markdown files
    md_files = glob_module.glob(os.path.join(directory, '**/*.md'), recursive=True)

    for file_path in md_files:
        with open(file_path, 'r', encoding='utf-8') as f:
            content = f.read()

        # Add frontmatter if missing
        if not content.startswith('---'):
            title = os.path.splitext(os.path.basename(file_path))[0]
            content = f'''---
title: {title}
---

{content}'''
            with open(file_path, 'w', encoding='utf-8') as f:
                f.write(content)

    return {'directory': directory}

Plugin.cs

using System.Text.RegularExpressions;

[PluginMain]
public static async Task<PluginOutput> Main(CyanPluginInput input)
{
    var directory = input.Directory;

    // Find all markdown files
    var mdFiles = Directory.GetFiles(directory, "*.md", SearchOption.AllDirectories);

    foreach (var filePath in mdFiles)
    {
        var content = await File.ReadAllTextAsync(filePath);

        // Add frontmatter if missing
        if (!content.StartsWith("---"))
        {
            var title = Path.GetFileNameWithoutExtension(filePath);
            content = $"---\ntitle: {title}\n---\n\n{content}";
            await File.WriteAllTextAsync(filePath, content);
        }
    }

    return new PluginOutput { Directory = directory };
}

All examples assume the imports shown in the first code block. When modifying files, be careful not to break the generated output. Test your plugin with various templates to ensure compatibility.

Run Shell Commands - Execute commands
Conditional Execution - Run based on config
Plugin Input/Output - API reference

Modify Generated Files

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