[ruby/rubygems] Print help summary when the default command fail

As mentioned in https://github.com/ruby/rubygems/issues/9124,
the intent for changing the default command was to be more welcoming.

I think we can acheive that by attempting to install, but to print
that same help message if there is no Gemfile.

That should address both concerns.

https://github.com/ruby/rubygems/commit/f3f505c02a

lib/bundler/cli.rb

@@ -120,10 +120,18 @@ module Bundler
       self.class.send(:class_options_help, shell)
     end
 
+    desc "install_or_cli_help", "Tries to run bundle install but prints a summary of bundler commands if there is no Gemfile", hide: true
+    def install_or_cli_help
+      invoke_other_command("install")
+    rescue GemfileNotFound => error
+      Bundler.ui.error error.message, wrap: true
+      invoke_other_command("cli_help")
+    end
+
     def self.default_command(meth = nil)
       return super if meth
 
-      Bundler.settings[:default_cli_command] || "install"
+      Bundler.settings[:default_cli_command] || "install_or_cli_help"
     end
 
     class_option "no-color", type: :boolean, desc: "Disable colorization in output"
@@ -713,6 +721,19 @@ module Bundler
       config[:current_command]
     end
 
+    def invoke_other_command(name)
+      _, _, config = @_initializer
+      original_command = config[:current_command]
+      command = self.class.all_commands[name]
+      config[:current_command] = command
+      send(name)
+    ensure
+      config[:current_command] = original_command
+    end
+
+    def current_command=(command)
+    end
+
     def print_command
       return unless Bundler.ui.debug?
       cmd = current_command

lib/bundler/vendor/thor/lib/thor.rb

@@ -625,7 +625,7 @@ class Bundler::Thor
     # alias name.
     def find_command_possibilities(meth)
       len = meth.to_s.length
-      possibilities = all_commands.merge(map).keys.select { |n| meth == n[0, len] }.sort
+      possibilities = all_commands.reject { |_k, c| c.hidden? }.merge(map).keys.select { |n| meth == n[0, len] }.sort
       unique_possibilities = possibilities.map { |k| map[k] || k }.uniq
 
       if possibilities.include?(meth)

spec/bundler/bundler/cli_spec.rb

@@ -87,27 +87,16 @@ RSpec.describe "bundle executable" do
   end
 
   context "with no arguments" do
-    it "installs by default" do
+    it "tries to installs by default but print help on missing Gemfile" do
       bundle "", raise_on_error: false
       expect(err).to include("Could not locate Gemfile")
-    end
 
-    it "prints a concise help message when default_cli_command set to cli_help" do
-      bundle "config set default_cli_command cli_help"
-      bundle ""
-      expect(err).to be_empty
       expect(out).to include("Bundler version #{Bundler::VERSION}").
         and include("\n\nBundler commands:\n\n").
         and include("\n\n  Primary commands:\n").
         and include("\n\n  Utilities:\n").
         and include("\n\nOptions:\n")
     end
-
-    it "runs bundle install when default_cli_command set to install" do
-      bundle "config set default_cli_command install"
-      bundle "", raise_on_error: false
-      expect(err).to include("Could not locate Gemfile")
-    end
   end
 
   context "when ENV['BUNDLE_GEMFILE'] is set to an empty string" do

spec/bundler/other/cli_dispatch_spec.rb

@@ -15,6 +15,6 @@ RSpec.describe "bundle command names" do
 
   it "print a friendly error when ambiguous" do
     bundle "in", raise_on_error: false
-    expect(err).to eq("Ambiguous command in matches [info, init, inject, install]")
+    expect(err).to eq("Ambiguous command in matches [info, init, install]")
   end
 end