Add ability to forward ARGV to a Pry session when using `bin/pry` (#1902)

* Add ability to forward ARGV to a Pry session when using `bin/pry`

Fixes https://github.com/pry/pry/issues/1901

lib/pry/cli.rb

@@ -59,11 +59,17 @@ class Pry
           raise NoOptionsError, "No command line options defined! Use Pry::CLI.add_options to add command line options."
         end
 
-        self.input_args = args
+        @pass_argv = args.index { |cli_arg| %w[- --].include?(cli_arg) }
+        if @pass_argv
+          slop_args = args[0...@pass_argv]
+          self.input_args = args.replace(args[@pass_argv + 1..-1])
+        else
+          self.input_args = slop_args = args
+        end
 
         begin
           opts = Pry::Slop.parse!(
-            args,
+            slop_args,
             help: true,
             multiple_switches: false,
             strict: true,
@@ -101,7 +107,7 @@ class Pry
           context = Pry.toplevel_binding
         end
 
-        if Pry::CLI.input_args.any? && Pry::CLI.input_args != ["pry"]
+        if !@pass_argv && Pry::CLI.input_args.any? && Pry::CLI.input_args != ["pry"]
           full_name = File.expand_path(Pry::CLI.input_args.first)
           Pry.load_file_through_repl(full_name)
           exit

spec/cli_spec.rb

@@ -1,4 +1,4 @@
-describe Pry::Hooks do
+RSpec.describe Pry::CLI do
   before do
     Pry::CLI.reset
   end

spec/integration/cli_spec.rb

@@ -1,17 +1,46 @@
 RSpec.describe 'The bin/pry CLI' do
   let(:ruby) { RbConfig.ruby.shellescape }
   let(:pry_dir) { File.expand_path(File.join(__FILE__, '../../../lib')).shellescape }
+  let(:clean_output) do
+    # Pry will emit silent garbage because of our auto indent feature.
+    # This lambda cleans the output of that garbage.
+    ->(out) { out.strip.sub("\e[0G", "") }
+  end
+
+  context "ARGV forwarding" do
+    let(:code) { "p(ARGV) and exit".shellescape }
+
+    it "forwards ARGV as an empty array when - is passed without following arguments" do
+      out = clean_output.call(`#{ruby} -I#{pry_dir} bin/pry -e #{code} -`)
+      expect(out).to eq([].inspect)
+    end
+
+    it "forwards ARGV as an empty array when -- is passed without following arguments" do
+      out = clean_output.call(`#{ruby} -I#{pry_dir} bin/pry -e #{code} --`)
+      expect(out).to eq([].inspect)
+    end
+
+    it "forwards its remaining arguments as ARGV when - is passed" do
+      out = clean_output.call(`#{ruby} -I#{pry_dir} bin/pry -e #{code} - 1 -foo --bar --baz daz`)
+      expect(out).to eq(%w[1 -foo --bar --baz daz].inspect)
+    end
+
+    it "forwards its remaining arguments as ARGV when -- is passed" do
+      out = clean_output.call(`#{ruby} -I#{pry_dir} bin/pry -e #{code} -- 1 -foo --bar --baz daz`)
+      expect(out).to eq(%w[1 -foo --bar --baz daz].inspect)
+    end
+  end
 
   context '-I path' do
     it 'adds an additional path to $LOAD_PATH' do
       code = 'p($LOAD_PATH) and exit'
-      out = `#{ruby} -I#{pry_dir} bin/pry -I /added/at/cli -e '#{code}'`
+      out = clean_output.call(`#{ruby} -I#{pry_dir} bin/pry -I /added/at/cli -e '#{code}'`)
       expect(out).to include('/added/at/cli')
     end
 
     it 'adds multiple additional paths to $LOAD_PATH' do
       code = 'p($LOAD_PATH) and exit'
-      out = `#{ruby} -I#{pry_dir} bin/pry -I /added-1/at/cli -I /added/at/cli/also -e '#{code}'`
+      out = clean_output.call(`#{ruby} -I#{pry_dir} bin/pry -I /added-1/at/cli -I /added/at/cli/also -e '#{code}'`)
       expect(out).to include('/added-1/at/cli')
       expect(out).to include('/added/at/cli/also')
     end