[WIP] Generic binary launcher

ruby/private/binary/BUILD.bazel

@@ -2,7 +2,8 @@ package(default_visibility = ["//ruby/private:__pkg__"])
 
 exports_files(
     [
-        "binary_wrapper.tpl",
+        "binary_launcher.tpl",
+        "main_binary_wrapper.tpl",
     ],
     visibility = ["//visibility:public"],
 )

ruby/private/binary/binary.bzl

@@ -59,6 +59,9 @@ def rb_binary_macro(ctx, main, srcs):
 
     executable = ctx.actions.declare_file(ctx.attr.name)
 
+    launcher_name = ctx.attr.name + "-launcher"
+    launcher_executable = ctx.actions.declare_file(launcher_name)
+
     deps = _transitive_deps(
         ctx,
         extra_files = [executable],
@@ -73,12 +76,12 @@ def rb_binary_macro(ctx, main, srcs):
     rubyopt = reversed(deps.rubyopt.to_list())
 
     ctx.actions.expand_template(
-        template = ctx.file._wrapper_template,
-        output = executable,
+        template = ctx.file._launcher_template,
+        output = launcher_executable,
         substitutions = {
             "{loadpaths}": repr(deps.incpaths.to_list()),
+            "{rule_name}": ctx.attr.name,
             "{rubyopt}": repr(rubyopt),
-            "{main}": repr(_to_manifest_path(ctx, main)),
             "{interpreter}": _to_manifest_path(ctx, interpreter),
             "{gem_path}": gem_path,
             "{bundle_path}": bundle_path,
@@ -88,9 +91,20 @@ def rb_binary_macro(ctx, main, srcs):
         },
     )
 
+    ctx.actions.expand_template(
+        template = ctx.file._wrapper_template,
+        output = executable,
+        substitutions = {
+            "{launcher_name}": launcher_name,
+            "{main}": repr(_to_manifest_path(ctx, main)),
+        },
+    )
+
+    runfiles = ctx.runfiles(files = [launcher_executable])
+    runfiles = runfiles.merge(deps.default_files.merge(deps.data_files))
     info = DefaultInfo(
         executable = executable,
-        runfiles = deps.default_files.merge(deps.data_files),
+        runfiles = runfiles,
     )
 
     return [info]

ruby/private/binary/binary_wrapper.tpl → ruby/private/binary/binary_launcher.tpl

@@ -21,7 +21,8 @@
 require 'rbconfig'
 
 def find_runfiles
-  stub_filename = File.absolute_path($0)
+  stub_dirname = File.dirname(File.absolute_path($0))
+  stub_filename = "#{stub_dirname}/{rule_name}"
   runfiles = "#{stub_filename}.runfiles"
   loop do
     case
@@ -113,6 +114,8 @@ def setup_gem_path(runfiles)
 end
 
 def main(args)
+  raise "Must provide target to launch" if args.empty?
+
   runfiles = find_runfiles
 
   runfiles_envkey, runfiles_envvalue = runfiles_envvar(runfiles)
@@ -128,7 +131,7 @@ def main(args)
 
   ruby_program = find_rb_binary
 
-  main = {main}
+  main = args.shift
   main = File.join(runfiles, main)
   rubyopt = {rubyopt}.map do |opt|
     opt.gsub(/\${(.+?)}/o) do

ruby/private/binary/main_binary_wrapper.tpl

@@ -0,0 +1,23 @@
+#!/usr/bin/env ruby
+
+if __FILE__ == $0
+  ##
+  # Find the launcher
+  ##
+
+  curr_file = File.absolute_path(__FILE__)
+  curr_dir = File.dirname(curr_file)
+
+  # Check if it is in this directory
+  if File.exists?("#{curr_dir}/{launcher_name}")
+    exec("#{curr_dir}/{launcher_name}", {main}, *ARGV)
+  end
+
+  # Check if this file is a symlink to the runfiles directory... then it will be there
+  if File.symlink?(curr_file) &&  %r!(.*\.runfiles)/.*!o =~ File.readlink(curr_file)
+    runfiles_dir = File.dirname(File.readlink(curr_file))
+    exec("#{runfiles_dir}/{launcher_name}", {main}, *ARGV)
+  end
+
+  raise "Could not find launcher file! This is likely an issue with rules_ruby"
+end

ruby/private/constants.bzl

@@ -30,7 +30,11 @@ RUBY_ATTRS = {
     ),
     "_wrapper_template": attr.label(
         allow_single_file = True,
-        default = "//ruby/private/binary:binary_wrapper.tpl",
+        default = "//ruby/private/binary:main_binary_wrapper.tpl",
+    ),
+    "_launcher_template": attr.label(
+        allow_single_file = True,
+        default = "//ruby/private/binary:binary_launcher.tpl",
     ),
     "_misc_deps": attr.label_list(
         allow_files = True,