Use vendor/cache for js gem to build extension as a part of "bundle install"

Author: kateinoigakukun

packages/gems/js/lib/js/version.rb

@@ -1,3 +1,3 @@
 module JS
-  VERSION = "2.6.2"
+  VERSION = "2.6.2.dev"
 end

packages/npm-packages/ruby-head-wasm-wasi/.gitignore

@@ -1,3 +1,4 @@
 *.tgz
 /tmp
 /bundle
+/vendor

packages/npm-packages/ruby-head-wasm-wasi/Gemfile

@@ -2,7 +2,14 @@
 
 source "https://rubygems.org"
 
-gem "js", path: "../../gems/js"
-gem "ruby_wasm", path: "../../../"
+# We build ./vendor/cache/js-local.gem just before evaluating this Gemfile
+# so that Bundler builds extensions even from the local gem. (gem extensions
+# from "path:" gems are not built by Bundler.)
+# Thus even we specify version of "js" gem here, it should always installed
+# from the ./vendor/cache/js-local.gem, not from rubygems.org. To achieve this,
+# we always use non-exist version during development.
+require_relative "../../gems/js/lib/js/version.rb"
+gem "js", JS::VERSION
+gem "ruby_wasm", path: "../../../", group: [:build]
 gem "power_assert"
 gem "test-unit"

rakelib/packaging.rake

@@ -67,6 +67,12 @@ namespace :npm do
         mkdir_p dist_dir
         if pkg[:target].start_with?("wasm32-unknown-wasi")
           Dir.chdir(cwd || base_dir) do
+            vendor_cache_dir = File.join(pkg_dir, "vendor", "cache")
+            mkdir_p vendor_cache_dir
+            require_relative "../packages/gems/js/lib/js/version"
+            sh "gem", "-C", File.join(base_dir, "packages/gems/js"), "build", "-o",
+              File.join(pkg_dir, "vendor", "cache", "js-local.gem")
+
             sh env,
                *build_command,
                "--no-stdlib",