gem: attempt to build a darwin gem that works on multiple darwin versions

.cross_rubies

@@ -2,19 +2,19 @@
 2.7.0:x86_64-w64-mingw32
 2.7.0:i686-linux-gnu
 2.7.0:x86_64-linux-gnu
-2.7.0:x86_64-darwin19
+2.7.0:x86_64-darwin
 2.6.0:i686-w64-mingw32
 2.6.0:x86_64-w64-mingw32
 2.6.0:i686-linux-gnu
 2.6.0:x86_64-linux-gnu
-2.6.0:x86_64-darwin19
+2.6.0:x86_64-darwin
 2.5.0:i686-w64-mingw32
 2.5.0:x86_64-w64-mingw32
 2.5.0:i686-linux-gnu
 2.5.0:x86_64-linux-gnu
-2.5.0:x86_64-darwin19
+2.5.0:x86_64-darwin
 2.4.0:i686-w64-mingw32
 2.4.0:x86_64-w64-mingw32
 2.4.0:i686-linux-gnu
 2.4.0:x86_64-linux-gnu
-2.4.0:x86_64-darwin19
+2.4.0:x86_64-darwin

.gitignore

@@ -1,3 +1,4 @@
+.DS_Store
 *.gemspec
 *.tmproj
 *~

.hoerc

@@ -6,6 +6,7 @@ exclude: !ruby/regexp '/
        \.github|
        \.vagrant|
        \.yardoc|
+       \.DS_Store|
        concourse|
        gems|
        patches|

rakelib/cross-ruby.rake

@@ -46,8 +46,8 @@ CrossRuby = Struct.new(:version, :host) do
         "x86_64-linux"
       when /\Ai[3-6]86.*linux/
         "x86-linux"
-      when /\Ax86_64-darwin19/
-        "x86_64-darwin19"
+      when /\Ax86_64-darwin/
+        "x86_64-darwin"
       else
         raise "CrossRuby.platform: unsupported host: #{host}"
       end
@@ -63,8 +63,8 @@ CrossRuby = Struct.new(:version, :host) do
         "x86_64-linux-gnu-"
       when "x86-linux"
         "i686-linux-gnu-"
-      when /darwin/
-        ""
+      # when /darwin/
+      #   ""
       else
         raise "CrossRuby.tool: unmatched platform: #{platform}"
       end) + name
@@ -80,8 +80,8 @@ CrossRuby = Struct.new(:version, :host) do
       "elf64-x86-64"
     when "x86-linux"
       "elf32-i386"
-    when "x86_64-darwin19"
-      "Mach-O 64-bit x86-64"
+    when "x86_64-darwin"
+      "Mach-O 64-bit x86-64" # hmm
     else
       raise "CrossRuby.target_file_format: unmatched platform: #{platform}"
     end

scripts/setup-osx-native-builders

@@ -4,6 +4,9 @@
 # - https://github.com/rake-compiler/rake-compiler/blob/master/tasks/bin/cross-ruby.rake
 # - https://github.com/apolcyn/grpc/blob/master/tools/distrib/build_ruby_environment_macos.sh
 
+# see test/test_gem_platform.rb for context
+gem_platform_name="x86_64-darwin"
+
 # chosen so chruby will see it, should you be a user of chruby
 RUBIES_DIR=${HOME}/.rubies
 
@@ -18,11 +21,12 @@ set -o pipefail
 
 CROSS_FILE=".cross_rubies"
 RUBIES=$(cat $CROSS_FILE | fgrep darwin | cut -d. -f1,2 | sort -u)
+
 RAKE_COMPILER_CONFIG_DIR=${HOME}/.rake-compiler
 RAKE_COMPILER_CONFIG=${RAKE_COMPILER_CONFIG_DIR}/config.yml
+TMP_CONFIG=$(mktemp /tmp/rake-compiler-config.XXXXXXXX)
 
-mkdir -p $RAKE_COMPILER_CONFIG_DIR
-echo "---" > $RAKE_COMPILER_CONFIG
+echo "---" > $TMP_CONFIG
 
 for ruby in $RUBIES ; do
   ruby_fullname="native-builder-${ruby}"
@@ -42,9 +46,9 @@ for ruby in $RUBIES ; do
     echo "ruby $ruby_fullname is installed"
   fi
 
-  platform=$(basename $(dirname $rbconfig))
-
-  echo "rbconfig-${platform}-${ruby_minor}: \"${rbconfig}\"" >> $RAKE_COMPILER_CONFIG
+  echo "rbconfig-${gem_platform_name}-${ruby_minor}: \"${rbconfig}\"" >> $TMP_CONFIG
 done
 
+mkdir -p $RAKE_COMPILER_CONFIG_DIR
+cp $TMP_CONFIG $RAKE_COMPILER_CONFIG
 cat $RAKE_COMPILER_CONFIG

test/test_gem_platform.rb

@@ -0,0 +1,69 @@
+require "helper"
+
+class TestGemPlatform < Nokogiri::TestCase
+  # These tests were written to help me better understand the behavior
+  # of Rubygems's platform-matching behavior. They don't exercise code
+  # in Nokogiri, but do express the expectations we have of Rubygems
+  # and `gem install` behavior for our native darwin gem.
+  #
+  # More specifically, the grpc gem ships a native darwin gem with
+  # platform string `universal-darwin` which I *think* refers to the
+  # fact that it supports i386-and-x86_64 architectures (and not that
+  # it supports x86_64-and-arm64 architectures).
+  #
+  # With ARM support imminent [1] I'm a little worried about using
+  # `universal` until I understand better whether ARM support will be
+  # implied by `universal` or `universal2` or what. From
+  # https://en.wikipedia.org/wiki/Universal_binary:
+  #
+  # > The new Universal 2 binary format was introduced at the 2020
+  # > Worldwide Developers Conference. Universal 2 allows applications
+  # > to run on both Intel x86-64-based and ARM64-based Macintosh
+  # > computers, for the Mac transition to Apple Silicon.
+  #
+  # [1]: https://arstechnica.com/gadgets/2020/06/this-is-apples-roadmap-for-moving-the-first-macs-away-from-intel/
+  #
+  # There seems to be a lot of uncertainty right now, so I'm writing
+  # some tests to express my expectations, and we're gonig to
+  # conservatively use `x86_64-darwin` as the platform name for the
+  # native gem.
+  let(:darwin_gem_platform) { Gem::Platform.new("x86_64-darwin") }
+
+  describe "darwin" do
+    it "builds a gem that works on all darwin x86+64 platforms" do
+      assert_match darwin_gem_platform,
+                   Gem::Platform.new(["universal", "darwin", "19"]),
+                   "gem should match system-installed ruby on catalina"
+      assert_match darwin_gem_platform,
+                   Gem::Platform.new(["x86_64", "darwin", "19"]),
+                   "gem should match user-installed ruby on catalina"
+      assert_match darwin_gem_platform,
+                   Gem::Platform.new(["x86_64", "darwin", "18"]),
+                   "gem should match user-installed ruby on mojave"
+
+      # The intention here is to test that the x86_64 platform gems
+      # won't match a future ruby that is compiled on arm64/aarch64.
+      #
+      # I don't know what the future platform will call itself, but at
+      # least one of these should be right and none of them should
+      # match, so here are all the tests I can reasonably imagine.
+      #
+      # Feel free to delete assertions for clarity once we know more.
+      assert_no_match darwin_gem_platform,
+                      Gem::Platform.new(["arm64", "darwin", "19"]),
+                      "gem should not match an arm64 ruby"
+      assert_no_match darwin_gem_platform,
+                      Gem::Platform.new(["arm", "darwin", "19"]),
+                      "gem should not match an arm ruby"
+      assert_no_match darwin_gem_platform,
+                      Gem::Platform.new(["aarch64", "darwin", "19"]),
+                      "gem should not match an aarch64 ruby"
+      assert_no_match darwin_gem_platform,
+                      Gem::Platform.new(["universal2", "darwin", "19"]),
+                      "gem should not match an aarch64 ruby"
+      assert_no_match darwin_gem_platform,
+                      Gem::Platform.new(["universal_2", "darwin", "19"]),
+                      "gem should not match an aarch64 ruby"
+    end
+  end
+end