Mirroring with custom host much harder compared with node-pre-gyp

[Fiouz]

Context

• Hosting of binary on custom host
• Package with working mirroring migrated from node-pre-gyp to prebuild-install
  • Migration did not change host

• prebuild-install/util.js

  Lines 46 to 60 in 8250adf

  	if (hostMirrorUrl) {
  	return hostMirrorUrl + '/{tag_prefix}{version}/' + packageName
  	}
  	if (opts.pkg.binary && opts.pkg.binary.host) {
  	return [
  	opts.pkg.binary.host,
  	opts.pkg.binary.remote_path,
  	opts.pkg.binary.package_name || packageName
  	].map(function (path) {
  	return trimSlashes(path)
  	}).filter(Boolean).join('/')
  	}
  	return github(opts.pkg) + '/releases/download/{tag_prefix}{version}/' + packageName

Issue

Even though prebuild-install seems to have a similar option set compared to node-pre-gyp, mirroring is much harder to achieve and requires proper planning from the package maintainer.

Requirements for mirroring a binary that relies on node-pre-gyp:

• (consumer) Mirror the <package.json>.binary.host
• (consumer) Configure the npm <package>_binary_host_mirror variable to point to the mirror

Requirements for mirroring a binary that relies on prebuild-install with a custom host:

• (package maintainer) Need to make sure that <package.json>.binary.remote_path ends with the hardcoded /{tag_prefix}{version}/ pattern. In case remote_path does not already include {tag_prefix}, prebuild-install must be invoked with --tag-prefix=
• (consumer) Mirror the <package.json>.binary.host
• (consumer) In case interoperability with node-pre-gyp is needed (e.g. case of realm library)
  • use the <package>_binary_host npm variable, and keep <package>_binary_host_mirror unchanged
  • configure <package>_binary_host npm variable to include whatever is needed so that the concatenation of <package>_binary_host + /{tag_prefix}{version}/ (taking into consideration that {tag_prefix} is controlled by package maintainer) matches the HTTP mirror

An example of such difficulty can be seen at realm/realm-js#4667 (comment)

Is there a chance to simplify binary mirroring?