From ab186266b7bc249696bb081e55746f26f1451682 Mon Sep 17 00:00:00 2001
From: bronzdoc <lsagastume1990@gmail.com>
Date: Sun, 18 Aug 2019 14:57:41 -0600
Subject: [PATCH] Build the first gemspec we found if no gemspec is specified

---
 lib/rubygems/commands/build_command.rb        | 10 ++++-
 .../test_gem_commands_build_command.rb        | 39 +++++++++++++++++++
 2 files changed, 48 insertions(+), 1 deletion(-)

diff --git a/lib/rubygems/commands/build_command.rb b/lib/rubygems/commands/build_command.rb
index bc37ab9a949f..69203d3ebca2 100644
--- a/lib/rubygems/commands/build_command.rb
+++ b/lib/rubygems/commands/build_command.rb
@@ -57,11 +57,19 @@ def usage # :nodoc:
   end
 
   def execute
-    build_gem
+    build_gem(gem_name)
   end
 
   private
 
+  def gem_name
+    get_one_optional_argument || find_gemspecs.first
+  end
+
+  def find_gemspecs
+    Dir.glob("*.gemspec").sort
+  end
+
   def build_gem(gem_name = get_one_optional_argument)
     gemspec = File.exist?(gem_name) ? gem_name : "#{gem_name}.gemspec"
 
diff --git a/test/rubygems/test_gem_commands_build_command.rb b/test/rubygems/test_gem_commands_build_command.rb
index 6d44d48c13f4..3edd7d4e4bc3 100644
--- a/test/rubygems/test_gem_commands_build_command.rb
+++ b/test/rubygems/test_gem_commands_build_command.rb
@@ -242,6 +242,45 @@ def test_can_find_gemspecs_without_dot_gemspec
     util_test_build_gem @gem
   end
 
+  def test_execute_without_gem_name
+    some_gem = util_spec "some_gem" do |s|
+      s.license = "AGPL-3.0"
+      s.files = ["README.md"]
+    end
+
+    gemspec_dir  = File.join(@tempdir, "build_command_gem")
+    gemspec_file = File.join(gemspec_dir, some_gem.spec_name)
+    readme_file  = File.join(gemspec_dir, 'README.md')
+
+    FileUtils.mkdir_p(gemspec_dir)
+
+    File.open(readme_file, "w") do |f|
+      f.write("My awesome gem")
+    end
+
+    File.open(gemspec_file, "w") do |gs|
+      gs.write(some_gem.to_ruby)
+    end
+
+    @cmd.options[:args] = []
+
+    use_ui @ui do
+      Dir.chdir(gemspec_dir) do
+        @cmd.execute
+      end
+    end
+
+    output = @ui.output.split("\n")
+    assert_equal "  Successfully built RubyGem", output.shift
+    assert_equal "  Name: some_gem", output.shift
+    assert_equal "  Version: 2", output.shift
+    assert_equal "  File: some_gem-2.gem", output.shift
+    assert_equal [], output
+
+    some_gem = File.join(gemspec_dir, File.basename(some_gem.cache_file))
+    assert File.exist?(some_gem)
+  end
+
   def util_test_build_gem(gem)
     use_ui @ui do
       Dir.chdir @tempdir do