| # turbopack-ecmascript-runtime | |
| This crate contains Turbopack's ECMAScript runtimes. These include: | |
| - Development runtimes for the browser, Node.js, and Edge-like runtimes; | |
| - Production runtimes for the browser, Node.js, and Edge-like runtimes (only Node.js is implemented for now). | |
| ## `<reference path="...">` | |
| The TypeScript files corresponding to the runtime itself all use `<reference path="...">` instead of `import`/`export` | |
| to import dependencies. This is because the runtime doesn't use a module system. Instead, the files are concatenated | |
| together in a specific order. | |
| As such, the `<reference path="...">` statements more closely map to the way the runtime is actually built. They also | |
| allow us to refer to top-level declarations in another file without having to `import`/`export` them, which makes no | |
| sense in the context of a runtime. | |
| ## Why is everything in one crate? | |
| The runtime-agnostic code (`js/src/shared`) was originally placed in `turbopack-ecmascript`, and the runtime-specific | |
| code (`js/src/{build,dev}`) in `turbopack-{build,dev}`. | |
| However, `<reference path="...">` statements only support relative paths. You can't refer to a file in a dependency. For | |
| the typings to work properly, and for them to be usable from outside of this repo (e.g. in the Next.js repo), it's much | |
| easier to have everything in one package. | |
| ## Why so many `tsconfig.json`? | |
| Since different runtimes are meant to run in different environments, they use different `tsconfig.json` files to | |
| customize what APIs are available to them. For example, the browser runtime can use `window` and `document`, but the | |
| Node.js runtime can't. | |
| All of these `tsconfig.json` files extend `tsconfig.base.json`, which contains the common configuration for all | |
| runtimes. | |