deno-simple-module-loader

The deno_core crate, part of the Deno Javascript/Typescript runtime, provides a high-level interface over the V8 Javascript engine, with an event loop abstraction that integrates with Rust async code. This includes facilities for handling ES modules and dynamic imports.

However, deno_core does not by itself resolve and fetch modules. Instead it provides a ModuleLoader trait, alongside with two implementations: NoopModuleLoader, which fails when importing modules, and FsModuleLoader, which is limited to modules in the filesystem. deno_core does not provide an implementation of ModuleLoader which performs network requests, and the implementation in the Deno program is tightly coupled with Deno's network fetch infrastructure and with its Typescript compilation pipeline, so it can't be easily copied.

This crate provides a simple implementation of ModuleLoader that does load modules from the network, built on top of reqwest.

Things it supports:

• HTTP(S) imports
• Local filesystem imports
• Data URLs
• JSON modules (i.e. {type: "json"} import attributes just work)

Things it doesn't plan to support (but hey, file an issue if it bugs you):

• Any support at all for non-URL import specifiers (i.e. bare imports, like "lodash"), URL specifiers which are not supported in browsers (like Deno's npm: URL support), or any other mapping from the import specifier to the actual fetched URL (like import maps).
• Custom import attribute types (such as {type: "my-custom-type"}). CSS imports count as a custom type for this purpose.
• Blob URLs
• Any support for transpiling modules (i.e. Typescript)
• Custom network, authentication or TLS settings. (Though if there's significant demand, I might reconsider.)
• Running with a futures executor other than tokio.

deno-simple-module-loader doesn't work with versions of deno_core lower than 0.246.0. (The current version at the time of writing is 0.248.0).

This is a work in progress. No guarantees, yadda yadda.