From db70f8b94d9a37c26803d41e94266a2994df3e59 Mon Sep 17 00:00:00 2001
From: Josh Holtrop <jholtrop@gmail.com>
Date: Wed, 9 Jun 2021 22:48:30 -0400
Subject: [PATCH] Add "drop" grammar keyword to drop patterns

---
 lib/imbecile/grammar.rb |  3 +++
 spec/imbecile_spec.rb   | 13 +++++++++++++
 2 files changed, 16 insertions(+)

diff --git a/lib/imbecile/grammar.rb b/lib/imbecile/grammar.rb
index 80b3dfe..b268f7c 100644
--- a/lib/imbecile/grammar.rb
+++ b/lib/imbecile/grammar.rb
@@ -40,6 +40,9 @@ module Imbecile
           end
           @tokens << Token.new(name, pattern, @tokens.size)
           token_names << name
+        elsif line =~ /^\s*drop\s+(\S+)$/
+          pattern = $1
+          @tokens << Token.new(nil, pattern, @tokens.size)
         else
           raise Error.new("Unexpected input on line #{line_number}: #{line}")
         end
diff --git a/spec/imbecile_spec.rb b/spec/imbecile_spec.rb
index d175035..4ef47d4 100644
--- a/spec/imbecile_spec.rb
+++ b/spec/imbecile_spec.rb
@@ -103,6 +103,19 @@ EOF
 token foo
 token bar
 token WS \\s+
+EOF
+  end
+
+  it "allows dropping a matched pattern" do
+    expected = [
+      ["foo", "foo"],
+      [nil, " \t"],
+      ["bar", "bar"],
+    ]
+    expect(run(<<EOF, "foo \tbar")).to eq expected
+token foo
+token bar
+drop \\s+
 EOF
   end
 end