ReScript 12: Faster Builds & Modernized Dev Experience

ReScript 12: Under the Hood

ReScript 12.0's release is a significant step forward, particularly with its new build system. The intelligent dependency tracking and faster incremental builds directly address a pain point for developers working on larger projects and monorepos. The improvements to operators and dictionary literals also streamline common coding patterns, reducing boilerplate and improving code readability. The JSX preserve mode offers greater flexibility for integration with bundlers like ESBuild, enhancing the language's versatility. However, the adoption of ReScript remains a challenge. While the release addresses key performance and usability issues, the ecosystem and community around TypeScript are significantly larger. The breaking changes, while necessary, will require developers to invest time in migration, which could deter some. The article also doesn't provide detailed benchmarks comparing the performance of the new build system against the old one or against TypeScript's build times, which would have strengthened the analysis.

From a technical standpoint, the modular runtime architecture and platform-specific binaries are welcome improvements, contributing to a smaller installation footprint. The unified operator work is a pragmatic change that simplifies arithmetic operations. The introduction of dictionary literals with pattern matching is a valuable addition, especially for handling JSON payloads and configuration objects. The migration codemod is a helpful tool for easing the transition. However, the article doesn't delve into the specifics of the new build system's implementation (e.g., the underlying technologies used for dependency tracking or the build cache strategy) which could be of interest to developers looking to understand the technical details. Additionally, while the release notes mention the removal of JSX v3 support, a deeper explanation for this change and how it impacts existing code would be beneficial for developers.

Ultimately, ReScript 12 positions the language as a compelling alternative to TypeScript, particularly for those prioritizing type safety and build speed. The emphasis on developer experience and performance is commendable. The success of this release will depend on how effectively the ReScript team can communicate the benefits of the new features and make migration as smooth as possible. Further, continued community engagement and growth are crucial for long-term viability, and the project should focus on bridging the ecosystem gap with TypeScript to drive adoption.

Key Points

• New build system with intelligent dependency tracking and faster incremental builds addresses limitations in previous versions, especially for monorepos.
• Improved operator handling for arithmetic operations, including string concatenation, reduces boilerplate.
• Dictionary literals with pattern matching simplify JSON handling and configuration object destructuring.
• JSX preserve mode offers greater flexibility for integration with bundlers like ESBuild.
• Breaking changes include removal of JSX v3 support, new runtime package structure, and API naming changes.

---

📖 Source: ReScript 12.0 Released with New Build System