Resolution

What it is#

A beyond-resolution/1 document says which URL delivers each public specifier, for one target and one format. Every value is origin-relative: a canonical path plus the canonical query. One document therefore works on a development origin and on a published one, and a consumer prepends the origin it was configured with.

{
  "protocol": "beyond-resolution/1",
  "release": "r-42",
  "target": "browser",
  "format": "esm",
  "imports": {
    "@example/app": "/m/@example/[email protected]/modules/~root?target=browser&format=esm&env=production&min=true&sourcemap=external&types=false&css=false"
  },
  "scopes": {
    "/m/@example/[email protected]/": {
      "library/main": "/m/[email protected]/modules/main?target=browser&format=esm&env=production&min=true&sourcemap=external&types=false&css=false"
    }
  }
}

Members#

Rules#

• A specifier is one public module and is matched exactly. There are no prefix mappings. It resolves to a module path, or to a style path only when the specifier ends with .css (output selection). A specifier without .css never resolves to a stylesheet.
• A value is accepted only when the shared codec reads it and writes it back unchanged: the canonical path (no /m/npm/ alias), the canonical query, and the target and format of the document. A scheme, a host, a fragment or a missing query is rejected.
• A scope is an origin-relative path under /m/. A scope that ends with / matches every importer under it; any other scope matches one path. The longest scope that lists the specifier wins, and imports answers otherwise.
• A document that breaks a rule is rejected with RESOLUTION_INVALID. This is an error of the client-side codec; it is not one of the HTTP error codes of the delivery routes.

Scopes are how two versions of one package coexist in one application: the modules of @example/legacy above keep [email protected] while everyone else gets the version in imports.

The routes#

Every origin of the contract answers the resolution it serves, in two forms:

GET <base>/resolution.json[?target=<browser|node>&format=<esm|cjs|system>]    beyond-resolution/1, application/json
GET <base>/importmap.json[?target=<browser|node>&format=<esm|cjs|system>]     import map, application/importmap+json

• target and format go together, or neither: without them the service answers its default document. Any other option, a repeated one, an invalid value or one of the two alone is 400 OPTION_INVALID.
• importmap.json is the same resolution as a standard import map whose every address and scope key is relative to the document (./m/…). A consumer that loads the map from its URL resolves it on the origin that served it, path prefix included: Deno with --import-map=<base>/importmap.json?…, and SystemJS with <script type="systemjs-importmap" src="…">. A page that inlines a map resolves addresses against itself, so it needs absolute addresses: resolution.importmap(origin).
• The answers carry a strong ETag, answer If-None-Match with 304, and can be read by a page of another origin, like every resource of the contract.

Using it#

This example is executed by the verification harness of this site against the shared codec:

// Read a beyond-resolution/1 document with the shared codec. Its values are
// origin-relative, so the same document serves any base origin.
import { Resolution } from '@beyond-js/artifact-api';

const query = 'target=browser&format=esm&env=production&min=true&sourcemap=external&types=false&css=false';

const resolution = new Resolution({
	protocol: 'beyond-resolution/1',
	release: 'r-42',
	target: 'browser',
	format: 'esm',
	imports: {
		'@example/app': `/m/@example/[email protected]/modules/~root?${query}`,
		'library/main': `/m/[email protected]/modules/main?${query}`,
		// Only a specifier that ends with ".css" resolves to a stylesheet
		'@example/app/theme.css': `/m/@example/[email protected]/styles/theme?${query}`
	},
	scopes: {
		// Modules of @example/legacy keep the version of "library" they were tested with
		'/m/@example/[email protected]/': { 'library/main': `/m/[email protected]/modules/main?${query}` }
	}
});

const importer = '/m/@example/[email protected]/modules/widget';

console.log(resolution.resolve('library/main'));
console.log(resolution.resolve('library/main', importer));
console.log(resolution.url('https://cdn.example', '@example/app'));
console.log(resolution.resolve('@example/app/theme.css'));

// Absolute addresses, for a map inlined in a page of another origin
console.log(JSON.stringify(resolution.importmap('http://localhost:8080'), null, 2));
// Addresses relative to the document, as a service answers /importmap.json
console.log(JSON.stringify(resolution.importmap(), null, 2));

ResolutionRequest.parse(pathname, query) reads a request of either route and says which target and format it selects, for a service that implements them.

A release never re-resolves#

A release carries its resolution. The management API reports its location as urls.resolution of the release, as an origin-relative URL, and the backend closure of a target embeds the frozen resolution of that target. The resolution of a release never changes: promotion and rollback select a release, they do not re-resolve it.

Each environment consumes these documents in its own way; see Strategies per environment.