Projen Project Management

Expert guidance for working with projen-managed projects, including task execution, configuration management, and development workflows.

Overview

This skill provides comprehensive instructions for developing in projen-managed projects. Projen is a project configuration management tool that synthesizes project files from a single source of truth.

Core Principles

Task Execution

**Always use projen for running tasks** instead of npm, yarn, or other package managers directly:

```bash

Run tasks via projen

node ./projen.js <task-name>

Common tasks

node ./projen.js # Synthesize project configuration

node ./projen.js build # Build project (compile + test)

node ./projen.js test # Run tests only

node ./projen.js compile # Compile source code only

```

**Check available tasks** by inspecting `.projen/tasks.json` for all available tasks, descriptions, and steps.

File Modification Rules

**NEVER manually edit generated files.** Files marked with comments like "~~ Generated by projen. To modify..." are auto-generated and will be overwritten.

**Always modify configuration in `.projenrc`** files (`.projenrc.ts`, `.projenrc.py`, or `.projenrc.json`) instead:

1. Edit the `.projenrc` configuration file

2. Run `node ./projen.js` to regenerate project files

3. Review the synthesized changes

4. Commit both `.projenrc` and generated files

**Check `.projenrc` first** before suggesting changes to `package.json`, `tsconfig.json`, or other configuration files.

Dependency Management

**Add dependencies through projen configuration**, not by editing `package.json` directly.

Example in `.projenrc.ts`:

```typescript

project.addDeps('lodash'); // Runtime dependency

project.addDevDeps('jest'); // Dev dependency

project.addPeerDeps('react'); // Peer dependency

```

Standard Workflow

1. Make changes to `.projenrc` configuration file

2. Run `node ./projen.js` to synthesize and update generated files

3. Review the changes in generated files

4. Commit both `.projenrc` and the generated files together

Development Best Practices

Task Completion Criteria

A task is **not complete** until:

After Making Changes

Always run `node ./projen.js build` after modifying source or test files to ensure changes compile and pass all tests.

Developing Projen Itself

When contributing to the projen repository:

**Avoid full builds** - They take a long time. Run individual tasks directly instead.

**Run specific tests** for faster iteration:

```bash

node ./projen.js test test/path-to-test.test.ts

```

**Always run the linter** before committing:

```bash

node ./projen.js eslint

```

Use the linter frequently to ensure code is formatted correctly and follows best practices.

Key Files

Resources

Constraints