Add pattern matching variables expression lexeme

lib/gitlab/ci/pipeline/expression/lexeme/matches.rb

+module Gitlab
+  module Ci
+    module Pipeline
+      module Expression
+        module Lexeme
+          class Matches < Lexeme::Operator
+            PATTERN = /=~/.freeze
+
+            def initialize(left, right)
+              @left = left
+              @right = right
+            end
+
+            def evaluate(variables = {})
+              text = @left.evaluate(variables)
+              regexp = @right.evaluate(variables)
+
+              regexp.scan(text).any?
+            end
+
+            def self.build(_value, behind, ahead)
+              new(behind, ahead)
+            end
+          end
+        end
+      end
+    end
+  end
+end

spec/lib/gitlab/ci/pipeline/expression/lexeme/matches_spec.rb

+require 'fast_spec_helper'
+require_dependency 're2'
+
+describe Gitlab::Ci::Pipeline::Expression::Lexeme::Matches do
+  let(:left) { double('left') }
+  let(:right) { double('right') }
+
+  describe '.build' do
+    it 'creates a new instance of the token' do
+      expect(described_class.build('=~', left, right))
+        .to be_a(described_class)
+    end
+  end
+
+  describe '.type' do
+    it 'is an operator' do
+      expect(described_class.type).to eq :operator
+    end
+  end
+
+  describe '#evaluate' do
+    it 'returns false when left and right do not match' do
+      allow(left).to receive(:evaluate).and_return('my-string')
+      allow(right).to receive(:evaluate)
+        .and_return(Gitlab::UntrustedRegexp.new('something'))
+
+      operator = described_class.new(left, right)
+
+      expect(operator.evaluate).to eq false
+    end
+
+    it 'returns true when left and right match' do
+      allow(left).to receive(:evaluate).and_return('my-awesome-string')
+      allow(right).to receive(:evaluate)
+        .and_return(Gitlab::UntrustedRegexp.new('awesome.string$'))
+
+      operator = described_class.new(left, right)
+
+      expect(operator.evaluate).to eq true
+    end
+
+    it 'supports multiline strings' do
+      allow(left).to receive(:evaluate).and_return <<~TEXT
+        My awesome contents
+
+        My-text-string!
+      TEXT
+
+      allow(right).to receive(:evaluate)
+        .and_return(Gitlab::UntrustedRegexp.new('text-string'))
+
+      operator = described_class.new(left, right)
+
+      expect(operator.evaluate).to eq true
+    end
+  end
+end