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 or aims to support:

• HTTP(S) imports
• Local filesystem imports
• Data URLs
• JSON modules (i.e. import assertions will just work) (pending)

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

• Any support at all for "bare" import specifiers (i.e. "lodash", which aren't absolute or relative URLs). This means no support for import maps, or for Node.js's module resolution algorithm.
• 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 0.111.0 (corresponding to Deno 1.17.0), since that version slightly changed the ModuleSource API to support JSON modules.

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