From 2e3f3d030945b661fa78e254762dc33825593c32 Mon Sep 17 00:00:00 2001
From: William Woodruff <william@tuffbizz.com>
Date: Fri, 29 Sep 2017 18:31:28 -0400
Subject: [PATCH] Support for required options

This commit introduces support for required options,
which are options that cause the parser to raise
a `MissingRequiredOption` exception if not present.

Options can be marked as required by passing
`required: true` in their configuration, and any errors
caused by missing required options can be suppressed via
`suppress_errors: true`.
---
 lib/slop/error.rb  |  5 +++++
 lib/slop/option.rb |  1 +
 lib/slop/parser.rb |  7 +++++++
 test/error_test.rb | 14 ++++++++++++++
 4 files changed, 27 insertions(+)

diff --git a/lib/slop/error.rb b/lib/slop/error.rb
index b02de3b8..e0246458 100644
--- a/lib/slop/error.rb
+++ b/lib/slop/error.rb
@@ -32,4 +32,9 @@ def initialize(msg, flag)
       @flag = flag
     end
   end
+
+  # Raised when a required option is *not* parsed.
+  # Suppress with the `suppress_errors` config option.
+  class MissingRequiredOption < Error
+  end
 end
diff --git a/lib/slop/option.rb b/lib/slop/option.rb
index b8533aeb..b2e5f9b0 100644
--- a/lib/slop/option.rb
+++ b/lib/slop/option.rb
@@ -4,6 +4,7 @@ class Option
       help: true,
       tail: false,
       underscore_flags: true,
+      required: false,
     }
 
     # An Array of flags this option matches.
diff --git a/lib/slop/parser.rb b/lib/slop/parser.rb
index 3cba82b7..32cf3d8a 100644
--- a/lib/slop/parser.rb
+++ b/lib/slop/parser.rb
@@ -80,6 +80,13 @@ def parse(strings)
 
       @arguments += ignored_args
 
+      unused_options.each do |o|
+        if o.config[:required] && !suppress_errors?
+          pretty_flags = o.flags.map { |f| "`#{f}'" }.join(", ")
+          raise MissingRequiredOption, "missing required option #{pretty_flags}"
+        end
+      end
+
       Result.new(self).tap do |result|
         used_options.each { |o| o.finish(result) }
       end
diff --git a/test/error_test.rb b/test/error_test.rb
index 2f7730b6..d9c71ab7 100644
--- a/test/error_test.rb
+++ b/test/error_test.rb
@@ -49,3 +49,17 @@
     opts.parse %w(--foo)
   end
 end
+
+describe Slop::MissingRequiredOption do
+  it "raises when a required option is missing" do
+    opts = Slop::Options.new
+    opts.string "-n", "--name", required: true
+    assert_raises(Slop::MissingRequiredOption) { opts.parse [] }
+  end
+
+  it "does not raise when errors are suppressed" do
+    opts = Slop::Options.new(suppress_errors: true)
+    opts.string "-n", "--name", required: true
+    opts.parse []
+  end
+end