Add build_manifest.json concept for reproducible build

Author: kateinoigakukun

.gitignore

@@ -10,3 +10,5 @@ wapm_packages
 compile_commands.json
 
 html
+
+build_manifest.json

Rakefile

@@ -22,6 +22,18 @@ BUILD_SOURCES = {
   }
 }
 
+# Respect revisions specified in build_manifest.json, which is usually generated on GitHub Actions.
+if File.exist?("build_manifest.json")
+  begin
+    manifest = JSON.parse(File.read("build_manifest.json"))
+    manifest["ruby_revisions"].each do |name, rev|
+      BUILD_SOURCES[name]["rev"] = rev
+    end
+  rescue StandardError
+    $stderr.puts "Failed to load build_manifest.json"
+  end
+end
+
 FULL_EXTS =
   "bigdecimal,cgi/escape,continuation,coverage,date,dbm,digest/bubblebabble,digest,digest/md5,digest/rmd160,digest/sha1,digest/sha2,etc,fcntl,fiber,gdbm,json,json/generator,json/parser,nkf,objspace,pathname,psych,racc/cparse,rbconfig/sizeof,ripper,stringio,strscan,monitor,zlib,openssl"
 

tasks/ci.rake

@@ -1,3 +1,15 @@
+def latest_build_sources
+  BUILD_SOURCES.map do |name, src|
+    case src[:type]
+    when "github"
+      url = "https://api.github.com/repos/#{src[:repo]}/commits/#{src[:rev]}"
+      revision = OpenURI.open_uri(url) { |f| JSON.load(f.read) }
+      [name, revision["sha"]]
+    else
+      raise "#{src[:type]} is not supported to pin source revision"
+    end
+  end.to_h
+end
 namespace :ci do
   task :rake_task_matrix do
     require "pathname"
@@ -29,4 +41,9 @@ namespace :ci do
     end
     print JSON.generate(entries)
   end
+
+  task :build_manifest do
+    content = JSON.generate({ ruby_revisions: latest_build_sources })
+    File.write("build_manifest.json", content)
+  end
 end