[FEATURE] Support jsr: registry/protocol

[darcyclarke]

Description

JSR is npm compatible by offering their packages as scoped packages (ie. @jsr/*) & modifying the package names to be transformed with underscores instead of forward slashes delimitating the scope+name (ex. @luca/cases becomes @jsr/luca__cases).

Currently, users need to create a .npmrc file with a scoped config (ex. @jsr:registry=https://npm.jsr.io) & this will allow users of npm, pnpm, bun etc. to install those packages (ex. npm install @jsr/luca__cases@1). We can do better.

Suggestion

We should support a jsr: protocol by default in Spec/DepID so that user's don't need to use the weird double underscore pattern & define a scoped registry config. This kind of first-class support can net us some good-will from the Deno community & also helps them tell a more cohesive story for managing JSR packages (since the Deno runtime itself & deno.json files let users reference JSR packages as jsr:@luca/cases).

Implementation

• support jsr: by default in Spec
• transform the scope+name to be compatible for fetching from https://npm.jsr.io (ie. the definition jsr:@luca/cases will result in us fetching a Packument for @jsr/luca__cases from https://npm.jsr.io/) in pick-manifest

Example Fetch Manifest Logic

if (spec.namedRegistry === 'jsr') {
  const isScoped = spec.name[1] === '@'
  const parts = spec.name.split('/')
  const path = isScoped ? `${parts[0].substring(1)}__${parts[1]}` : spec.name
  const manifest = `${spec.registry}/@jsr/${path}`
}