"Generating Types without climbing a tree", Matteo Collina
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How do you generate types dynamically? How do you write a script that creates some typescript code? The approach most people would recommend is to use Abstract Syntax Tree manipulations. I was working on a deadline to implement types for our OpenAPI client, and I would have missed our release window. I needed something different and easier to build. Luckily, a friend recommended me a library I didn't know: code-block-writer. I fall in love with it at first sight.
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"Generating Types without climbing a tree", Matteo Collina
- 1. PLATFORMATIC.DEV Generating Types without climbing a tree @matteocollina | Co-Founder & CTO
- 2. PLATFORMATIC.DEV How many ropes do you need to climb a tree?
- 3. A little bit about me Matteo Collina, Ph.D. Co-Founder & CTO, Platformatic Node.js Technical Steering Committee member Board member OpenJS Foundation 8 years as a consultant focused on Node.js Created Fastify and Pino Subscribe to my newsletter at https://nodeland.dev.
- 5. 17 Billions Downloads / Year
- 6. After writing all this modules, I have a confession to make…
- 7. …before 2022, I almost never used TypeScript!
- 8. 2022
- 9. The process of building APIs
- 10. Platformatic.dev The fast backend development platform
- 11. A B C Enter Platformatic We are helping developers get rid of the undifferentiated heavy lifting of building Node.js applications
- 12. Let’s focus on the client!
- 13. A better flow
- 14. tRPC is amazing but… it introduces tight coupling
- 15. ts-rest is amazing but… it introduces tight coupling
- 16. Tight coupling lead to a monolith that’s very hard to break down
- 17. How can we produce an amazing developer experience without tight coupling between client and server?
- 18. According to all our surveys, ~80% of developers prefer REST to GraphQL
- 19. How can we automatically generate a client for our REST APIs? Ideally, the generated code should minimal and simple
- 20. OpenAPI is a standard way to define REST APIs Integrated in most frameworks Automatically generating OpenAPI documentation pages is simple.
- 21. Client generation: Requirements 1. Routes defined via OpenAPI 2. No data validation at runtime / let’s not waste any time on the client 3. Fully typed to catch developer mistakes via the editor (or at compile time) 4. Only use fetch() at runtime with no dependencies.
- 22. First try: Use the TypeScript compiler API Generating a simple function: Credits https://dev.to/rametta/typescript-code-generation-epn
- 23. First try: Use the TypeScript compiler API It took ~60 lines to generate 3. This is a 20x expansion.
- 24. A 20x expansion seem quite big tree to climb… and we did not want to climb any trees.
- 25. Second try: use call code-block-writer ~10 lines to generate 3. A ~3x expansion rate is a much better tradeoff. The code that generates the function is readable by a human. It’s homomorphic, because it maintains the relationship between the various part of our generated code. Warning: the generated code is not guaranteed to be valid!
- 26. code-block-writer looks like the lazy option!
- 29. From OpenAPI definitions to types ● Every path (route) defined in the OpenAPI specification has an optional operationId, which we can use to derive a method name from. If it’s missing, we can generate one! ● Split the types definition from the actual code that is being executed to increase debuggability (and support JavaScript, too!). ● Fully resolve shared schemas in the OpenAPI definitions and only generate 1 level types to avoid having the users reusing the defined types too much.
- 30. DEMO TIME! May the demo gods be with me
- 31. PLATFORMATIC.DEV Did we climb that tree?
- 32. Thanks! Try our open-source tools at docs.platformatic.dev @platformatic @matteocollina