Bazel vs Nix: What are the differences?

Introduction:

This Markdown code provides the key differences between Bazel and Nix, two popular build and package management tools. The differences are described in specific paragraphs, focusing on important aspects.

1. Build and Dependency Management Approach: Bazel follows a "build first" approach, focusing on reproducible builds and extensive caching to increase performance. It uses a workspace model, where the entire dependency graph is known upfront. On the other hand, Nix takes a "package first" approach, emphasizing determinism and purity. It builds packages by evaluating build expressions, allowing for highly reproducible environments.

2. Language Support: Bazel primarily supports languages like Java, C++, and Python. Its rule language, Starlark, allows for custom build and extension rules. Nix, in contrast, supports a broader range of languages and platforms, including but not limited to Haskell, Rust, and JavaScript. Nix also provides reproducible environments for any programming language.

3. Philosophy: Bazel aims to optimize build performance by aggressively caching and reusing build artifacts, resulting in fast and highly scalable builds. It encourages a strong separation between build and runtime, avoiding often unnecessary rebuilds. Nix, on the other hand, focuses on reproducibility and declarative package management. It promotes the idea of hermetic builds and fully deterministic outputs, enabling reliable and controlled deployments.

4. Scalability: Bazel is designed to handle large-scale projects with extensive dependencies and complex build requirements. It is optimized for incremental builds and parallel execution, allowing for faster development cycles. Nix, while also scalable, puts a stronger emphasis on deterministic and reproducible package management, making it suitable for both small and large-scale projects.

5. Ecosystem and Community: Bazel has a growing ecosystem, with a significant number of projects using it for their build and test infrastructure. It benefits from being an open-source project supported by a large community and backed by Google. Nix, although less known in comparison, has its own ecosystem and community, with a dedicated group of developers and users contributing to its development and maintenance.

6. Tool Features: Bazel provides various advanced features like remote cache, distributed build, and build farm integration, allowing for high-performance builds across clusters of machines. It also offers built-in support for testing frameworks like JUnit and PyTest, making it easier to write and execute tests. Nix, while not as feature-rich in terms of build optimizations, excels in its ability to create isolated and reproducible build environments, enabling precise control over dependencies and their versions.

In summary, Bazel focuses on reproducibility and highly optimized builds, primarily targeting Java, C++, and Python, with a growing community and advanced features. Nix, on the other hand, prioritizes determinism, broader language support, and declarative package management, providing reproducible environments for a wider range of programming languages.