Add lookup methods in `Variables::Collection`

Allows for quick lookup when expanding variable values.

lib/gitlab/ci/variables/collection.rb

@@ -10,13 +10,18 @@ module Gitlab
 
         def initialize(variables = [], errors = nil)
           @variables = []
+          @var_hash = {}
           @errors = errors
 
           variables.each { |variable| self.append(variable) }
         end
 
         def append(resource)
-          tap { @variables.append(Collection::Item.fabricate(resource)) }
+          tap do
+            item = Collection::Item.fabricate(resource)
+            @variables.append(item)
+            @var_hash[item[:key]] = item
+          end
         end
 
         def concat(resources)
@@ -36,10 +41,26 @@ module Gitlab
           end
         end
 
+        def [](key)
+          @var_hash[key]
+        end
+
+        def size
+          @variables.size
+        end
+
         def to_runner_variables
           self.map(&:to_runner_variable)
         end
 
+        def include?(obj)
+          return false unless obj.is_a?(Hash) && obj.has_key?(:key)
+
+          key = obj.fetch(:key)
+          found_var = @var_hash[key]
+          !found_var.nil? && found_var.to_runner_variable == Collection::Item.fabricate(obj).to_runner_variable
+        end
+
         def to_hash
           self.to_runner_variables
             .map { |env| [env.fetch(:key), env.fetch(:value)] }

spec/lib/gitlab/ci/variables/collection_spec.rb

@@ -98,6 +98,60 @@ RSpec.describe Gitlab::Ci::Variables::Collection do
     end
   end
 
+  describe '#[]' do
+    variable = { key: 'VAR', value: 'value', public: true, masked: false }
+
+    collection = described_class.new([variable])
+
+    it 'returns nil for a non-existent variable name' do
+      expect(collection['UNKNOWN_VAR']).to be_nil
+    end
+
+    it 'returns Item for an existent variable name' do
+      expect(collection['VAR']).to be_an_instance_of(Gitlab::Ci::Variables::Collection::Item)
+      expect(collection['VAR'].to_runner_variable).to eq(variable)
+    end
+  end
+
+  describe '#size' do
+    it 'returns zero for empty collection' do
+      collection = described_class.new([])
+
+      expect(collection.size).to eq(0)
+    end
+
+    it 'returns 2 for collection with 2 variables' do
+      collection = described_class.new(
+        [
+          { key: 'VAR1', value: 'value', public: true, masked: false },
+          { key: 'VAR2', value: 'value', public: true, masked: false }
+        ])
+
+      expect(collection.size).to eq(2)
+    end
+  end
+
+  describe '#include?' do
+    it 'returns false for unknown variable' do
+      collection = described_class.new([])
+
+      expect(collection.include?({ key: 'VAR', value: 'value', public: true, masked: false })).to eq(false)
+    end
+
+    it 'returns false for unsupported scenario of variable name argument' do
+      collection = described_class.new([{ key: 'VAR', value: 'value', public: true, masked: false }])
+
+      expect(collection.include?('VAR')).to eq(false)
+    end
+
+    it 'returns true for known variable' do
+      variable = { key: 'VAR', value: 'value', public: true, masked: false }
+      collection = described_class.new([variable])
+
+      expect(collection.include?(variable)).to eq(true)
+    end
+  end
+
   describe '#to_runner_variables' do
     it 'creates an array of hashes in a runner-compatible format' do
       collection = described_class.new([{ key: 'TEST', value: '1' }])