1 files changed, 359 insertions, 0 deletions
diff --git a/lib/rubygems/ext/cargo_builder.rb b/lib/rubygems/ext/cargo_builder.rb
new file mode 100644
index 0000000000..86a0e73f28
--- /dev/null
+++ b/lib/rubygems/ext/cargo_builder.rb
@@ -0,0 +1,359 @@
+# frozen_string_literal: true
+
+require_relative "../shellwords"
+
+# This class is used by rubygems to build Rust extensions. It is a thin-wrapper
+# over the `cargo rustc` command which takes care of building Rust code in a way
+# that Ruby can use.
+class Gem::Ext::CargoBuilder < Gem::Ext::Builder
+  attr_accessor :spec, :runner, :profile
+
+  def initialize
+    require_relative "../command"
+    require_relative "cargo_builder/link_flag_converter"
+
+    @runner = self.class.method(:run)
+    @profile = :release
+  end
+
+  def build(extension, dest_path, results, args = [], lib_dir = nil, cargo_dir = Dir.pwd)
+    require "tempfile"
+    require "fileutils"
+
+    # Where's the Cargo.toml of the crate we're building
+    cargo_toml = File.join(cargo_dir, "Cargo.toml")
+    # What's the crate's name
+    crate_name = cargo_crate_name(cargo_dir, cargo_toml, results)
+
+    begin
+      # Create a tmp dir to do the build in
+      tmp_dest = Dir.mktmpdir(".gem.", cargo_dir)
+
+      # Run the build
+      cmd = cargo_command(cargo_toml, tmp_dest, args, crate_name)
+      runner.call(cmd, results, "cargo", cargo_dir, build_env)
+
+      # Where do we expect Cargo to write the compiled library
+      dylib_path = cargo_dylib_path(tmp_dest, crate_name)
+
+      # Helpful error if we didn't find the compiled library
+      raise DylibNotFoundError, tmp_dest unless File.exist?(dylib_path)
+
+      # Cargo and Ruby differ on how the library should be named, rename from
+      # what Cargo outputs to what Ruby expects
+      dlext_name = "#{crate_name}.#{makefile_config("DLEXT")}"
+      dlext_path = File.join(File.dirname(dylib_path), dlext_name)
+      FileUtils.cp(dylib_path, dlext_path)
+
+      nesting = extension_nesting(extension)
+
+      if Gem.install_extension_in_lib && lib_dir
+        nested_lib_dir = File.join(lib_dir, nesting)
+        FileUtils.mkdir_p nested_lib_dir
+        FileUtils.cp_r dlext_path, nested_lib_dir, remove_destination: true
+      end
+
+      # move to final destination
+      nested_dest_path = File.join(dest_path, nesting)
+      FileUtils.mkdir_p nested_dest_path
+      FileUtils.cp_r dlext_path, nested_dest_path, remove_destination: true
+    ensure
+      # clean up intermediary build artifacts
+      FileUtils.rm_rf tmp_dest if tmp_dest
+    end
+
+    results
+  end
+
+  def build_env
+    build_env = rb_config_env
+    build_env["RUBY_STATIC"] = "true" if ruby_static? && ENV.key?("RUBY_STATIC")
+    cfg = "--cfg=rb_sys_gem --cfg=rubygems --cfg=rubygems_#{Gem::VERSION.tr(".", "_")}"
+    build_env["RUSTFLAGS"] = [ENV["RUSTFLAGS"], cfg].compact.join(" ")
+    build_env
+  end
+
+  def cargo_command(cargo_toml, dest_path, args = [], crate_name = nil)
+    cmd = []
+    cmd += [cargo, "rustc"]
+    cmd += ["--crate-type", "cdylib"]
+    cmd += ["--target", ENV["CARGO_BUILD_TARGET"]] if ENV["CARGO_BUILD_TARGET"]
+    cmd += ["--target-dir", dest_path]
+    cmd += ["--manifest-path", cargo_toml]
+    cmd += ["--lib"]
+    cmd += ["--profile", profile.to_s]
+    cmd += ["--locked"]
+    cmd += Gem::Command.build_args
+    cmd += args
+    cmd += ["--"]
+    cmd += [*cargo_rustc_args(dest_path, crate_name)]
+    cmd
+  end
+
+  private
+
+  def cargo
+    ENV.fetch("CARGO", "cargo")
+  end
+
+  # returns the directory nesting of the extension, ignoring the first part, so
+  # "ext/foo/bar/Cargo.toml" becomes "foo/bar"
+  def extension_nesting(extension)
+    parts = extension.to_s.split(Regexp.union([File::SEPARATOR, File::ALT_SEPARATOR].compact))
+
+    parts = parts.each_with_object([]) do |segment, final|
+      next if segment == "."
+      if segment == ".."
+        raise Gem::InstallError, "extension outside of gem root" if final.empty?
+        next final.pop
+      end
+      final << segment
+    end
+
+    File.join(parts[1...-1])
+  end
+
+  def rb_config_env
+    result = {}
+    RbConfig::CONFIG.each {|k, v| result["RBCONFIG_#{k}"] = v }
+    result
+  end
+
+  def cargo_rustc_args(dest_dir, crate_name)
+    [
+      *linker_args,
+      *mkmf_libpath,
+      *rustc_dynamic_linker_flags(dest_dir, crate_name),
+      *rustc_lib_flags(dest_dir),
+      *platform_specific_rustc_args(dest_dir),
+    ]
+  end
+
+  def platform_specific_rustc_args(dest_dir, flags = [])
+    if mingw_target?
+      # On mingw platforms, mkmf adds libruby to the linker flags
+      flags += libruby_args(dest_dir)
+
+      # Make sure ALSR is used on mingw
+      # see https://github.com/rust-lang/rust/pull/75406/files
+      flags += ["-C", "link-arg=-Wl,--dynamicbase"]
+      flags += ["-C", "link-arg=-Wl,--disable-auto-image-base"]
+
+      # If the gem is installed on a host with build tools installed, but is
+      # run on one that isn't the missing libraries will cause the extension
+      # to fail on start.
+      flags += ["-C", "link-arg=-static-libgcc"]
+    elsif darwin_target?
+      # Ventura does not always have this flag enabled
+      flags += ["-C", "link-arg=-Wl,-undefined,dynamic_lookup"]
+    end
+
+    flags
+  end
+
+  # We want to use the same linker that Ruby uses, so that the linker flags from
+  # mkmf work properly.
+  def linker_args
+    cc_flag = Shellwords.split(makefile_config("CC"))
+    linker = cc_flag.shift
+    link_args = cc_flag.flat_map {|a| ["-C", "link-arg=#{a}"] }
+
+    return mswin_link_args if linker == "cl"
+
+    ["-C", "linker=#{linker}", *link_args]
+  end
+
+  def mswin_link_args
+    args = []
+    args += ["-l", makefile_config("LIBRUBYARG_SHARED").chomp(".lib")]
+    args += split_flags("LIBS").flat_map {|lib| ["-l", lib.chomp(".lib")] }
+    args += split_flags("LOCAL_LIBS").flat_map {|lib| ["-l", lib.chomp(".lib")] }
+    args
+  end
+
+  def libruby_args(dest_dir)
+    libs = makefile_config(ruby_static? ? "LIBRUBYARG_STATIC" : "LIBRUBYARG_SHARED")
+    raw_libs = Shellwords.split(libs)
+    raw_libs.flat_map {|l| ldflag_to_link_modifier(l) }
+  end
+
+  def ruby_static?
+    return true if %w[1 true].include?(ENV["RUBY_STATIC"])
+
+    makefile_config("ENABLE_SHARED") == "no"
+  end
+
+  def cargo_dylib_path(dest_path, crate_name)
+    prefix = so_ext == "dll" ? "" : "lib"
+    path_parts = [dest_path]
+    path_parts << ENV["CARGO_BUILD_TARGET"] if ENV["CARGO_BUILD_TARGET"]
+    path_parts += ["release", "#{prefix}#{crate_name}.#{so_ext}"]
+    File.join(*path_parts)
+  end
+
+  def cargo_crate_name(cargo_dir, manifest_path, results)
+    require "open3"
+    Gem.load_yaml
+
+    output, status =
+      begin
+        Open3.capture2e(cargo, "metadata", "--no-deps", "--format-version", "1", chdir: cargo_dir)
+      rescue StandardError => error
+        raise Gem::InstallError, "cargo metadata failed #{error.message}"
+      end
+
+    unless status.success?
+      if Gem.configuration.really_verbose
+        puts output
+      else
+        results << output
+      end
+
+      exit_reason =
+        if status.exited?
+          ", exit code #{status.exitstatus}"
+        elsif status.signaled?
+          ", uncaught signal #{status.termsig}"
+        end
+
+      raise Gem::InstallError, "cargo metadata failed#{exit_reason}"
+    end
+
+    # cargo metadata output is specified as json, but with the
+    # --format-version 1 option the output is compatible with YAML, so we can
+    # avoid the json dependency
+    metadata = Gem::SafeYAML.safe_load(output)
+    package = metadata["packages"].find {|pkg| normalize_path(pkg["manifest_path"]) == manifest_path }
+    unless package
+      found = metadata["packages"].map {|md| "#{md["name"]} at #{md["manifest_path"]}" }
+      raise Gem::InstallError, <<-EOF
+failed to determine cargo package name
+
+looking for: #{manifest_path}
+
+found:
+#{found.join("\n")}
+EOF
+    end
+    package["name"].tr("-", "_")
+  end
+
+  def normalize_path(path)
+    return path unless File::ALT_SEPARATOR
+
+    path.tr(File::ALT_SEPARATOR, File::SEPARATOR)
+  end
+
+  def rustc_dynamic_linker_flags(dest_dir, crate_name)
+    split_flags("DLDFLAGS").
+      map {|arg| maybe_resolve_ldflag_variable(arg, dest_dir, crate_name) }.
+      compact.
+      flat_map {|arg| ldflag_to_link_modifier(arg) }
+  end
+
+  def rustc_lib_flags(dest_dir)
+    split_flags("LIBS").flat_map {|arg| ldflag_to_link_modifier(arg) }
+  end
+
+  def split_flags(var)
+    Shellwords.split(RbConfig::CONFIG.fetch(var, ""))
+  end
+
+  def ldflag_to_link_modifier(arg)
+    LinkFlagConverter.convert(arg)
+  end
+
+  def msvc_target?
+    makefile_config("target_os").include?("msvc")
+  end
+
+  def darwin_target?
+    makefile_config("target_os").include?("darwin")
+  end
+
+  def mingw_target?
+    makefile_config("target_os").include?("mingw")
+  end
+
+  def win_target?
+    target_platform = RbConfig::CONFIG["target_os"]
+    !!Gem::WIN_PATTERNS.find {|r| target_platform =~ r }
+  end
+
+  # Interpolate substitution vars in the arg (i.e. $(DEFFILE))
+  def maybe_resolve_ldflag_variable(input_arg, dest_dir, crate_name)
+    var_matches = input_arg.match(/\$\((\w+)\)/)
+
+    return input_arg unless var_matches
+
+    var_name = var_matches[1]
+
+    return input_arg if var_name.nil? || var_name.chomp.empty?
+
+    case var_name
+    # On windows, it is assumed that mkmf has setup an exports file for the
+    # extension, so we have to create one ourselves.
+    when "DEFFILE"
+      write_deffile(dest_dir, crate_name)
+    else
+      RbConfig::CONFIG[var_name]
+    end
+  end
+
+  def write_deffile(dest_dir, crate_name)
+    deffile_path = File.join(dest_dir, "#{crate_name}-#{RbConfig::CONFIG["arch"]}.def")
+    export_prefix = makefile_config("EXPORT_PREFIX") || ""
+
+    File.open(deffile_path, "w") do |f|
+      f.puts "EXPORTS"
+      f.puts "#{export_prefix.strip}Init_#{crate_name}"
+    end
+
+    deffile_path
+  end
+
+  # We have to basically reimplement <code>RbConfig::CONFIG['SOEXT']</code> here to support
+  # Ruby < 2.5
+  #
+  # @see https://github.com/ruby/ruby/blob/c87c027f18c005460746a74c07cd80ee355b16e4/configure.ac#L3185
+  def so_ext
+    return RbConfig::CONFIG["SOEXT"] if RbConfig::CONFIG.key?("SOEXT")
+
+    if win_target?
+      "dll"
+    elsif darwin_target?
+      "dylib"
+    else
+      "so"
+    end
+  end
+
+  # Corresponds to $(LIBPATH) in mkmf
+  def mkmf_libpath
+    ["-L", "native=#{makefile_config("libdir")}"]
+  end
+
+  def makefile_config(var_name)
+    val = RbConfig::MAKEFILE_CONFIG[var_name]
+
+    return unless val
+
+    RbConfig.expand(val.dup)
+  end
+
+  # Error raised when no cdylib artifact was created
+  class DylibNotFoundError < StandardError
+    def initialize(dir)
+      files = Dir.glob(File.join(dir, "**", "*")).map {|f| "- #{f}" }.join "\n"
+
+      super <<~MSG
+        Dynamic library not found for Rust extension (in #{dir})
+
+        Make sure you set "crate-type" in Cargo.toml to "cdylib"
+
+        Found files:
+        #{files}
+      MSG
+    end
+  end
+end