esbuild_deno_loader

Deno module resolution for esbuild.

  • Support for file:, https:, and data: specifiers
  • Support for npm: specifiers
  • Support for import maps (including embedded into deno.json)
  • Native loader using Deno's global cache directory
  • Portable loader that words in environments with limited permissions

Example

This example bundles an entrypoint into a single ESM output.

import * as esbuild from "https://deno.land/x/esbuild@v0.19.11/mod.js";
// Import the WASM build on platforms where running subprocesses is not
// permitted, such as Deno Deploy, or when running without `--allow-run`.
// import * as esbuild from "https://deno.land/x/esbuild@v0.19.11/wasm.js";

import { denoPlugins } from "https://deno.land/x/esbuild_deno_loader@0.8.4/mod.ts";

const result = await esbuild.build({
  plugins: [...denoPlugins()],
  entryPoints: ["https://deno.land/std@0.185.0/bytes/mod.ts"],
  outfile: "./dist/bytes.esm.js",
  bundle: true,
  format: "esm",
});

console.log(result.outputFiles);

esbuild.stop();

Limitations

  • The "portable" loader does not use the Deno module cache, so all remote specifiers are downloaded on every run.
  • When using the "portable" loader, all npm: dependencies must be pre-downloaded into a local node_modules/ directory.
  • npm: specifiers are not supported on WASM esbuild builds due to FS access limitations (see https://github.com/evanw/esbuild/pull/2968).

Documentation

The Deno integration for Deno consists of two separate plugins (that are however most commonly used together):

  1. The resolver, which resolves specifiers within a file relative to the file itself (absolutization), taking into account import maps.
  2. The loader, which takes a fully resolved specifier, and attempts to load it. If the loader encounters redirects, these are processed until a final module is found.

Most commonly these two plugins are used together, chained directly after each other using the denoPlugins() function. This function returns an array of esbuild.Plugin instances, which can be spread directly into the plugins array of the esbuild build options.

In depth documentation for each of the plugins, and the denoPlugins() function can be found in the generated docs.

Using with other plugins

For some use-cases these plugins should be manually instantiated. For example if you want to add your own loader plugins that handles specific file extensions or URL schemes, you should insert these plugins between the Deno resolver, and Deno loader.

In most cases, the denoResolverPlugin should be the first plugin in the plugin array.

The resolver performs initial resolution on the path. This includes making relative specifiers absolute and processing import maps. It will then send the fully resolved specifiers back into esbuild's resolver stack to be processed by other plugins. In the second path, the representation of the module is a fully qualified URL. The namespace of the second resolve pass is the scheme of the URL. The path is the remainder of the URL. The second resolve pass does not have a resolveDir property, as the URL is fully qualified already.

The denoLoaderPlugin registers resolvers that are hit in the secondary resolve pass for the schemes http, https, data, and file.

The output of the second resolve pass is then passed to the loader stack. The loader stack is responsible for loading the module. Just like in the resolver stack, the namespace of the loader stack is the scheme of the URL, and the path is the remainder of the URL.

The denoLoaderPlugin registers loaders that are hit in the secondary resolve pass for the schemes http, https, data, and file.

The examples directory contains an example for how to integrate with custom plugins. The examples/custom_scheme_plugin.ts example shows how to add a plugin that handles a custom scheme.

Permissions

This plugins requires the following permissions:

  • --allow-read if you need to resolve local files.
  • --allow-net if you need to resolve remote files.

If the program is run with --allow-run, the plugin will use the deno binary to resolve remote files. This allows the plugin to re-use the Deno module cache.