Add support for evaluating pipeline expression variables

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

@@ -11,7 +11,7 @@ module Gitlab
               @right = right
             end
 
-            def evaluate(**variables)
+            def evaluate(variables)
               @left.evaluate(variables) == @right.evaluate(variables)
             end
 

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

@@ -10,9 +10,13 @@ module Gitlab
               @value = value
             end
 
-            def evaluate(**_)
+            def evaluate(_)
               nil
             end
+
+            def self.build(value)
+              new(value)
+            end
           end
         end
       end

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

@@ -10,7 +10,7 @@ module Gitlab
               @value = value
             end
 
-            def evaluate(**_)
+            def evaluate(_)
               @value.to_s
             end
 

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

@@ -10,7 +10,8 @@ module Gitlab
               @name = name
             end
 
-            def evaluate(**variables)
+            def evaluate(variables)
+              variables[@name]
             end
 
             def self.build(string)

lib/gitlab/ci/pipeline/expression/lexer.rb

@@ -6,6 +6,7 @@ module Gitlab
           LEXEMES = [
             Expression::Lexeme::Variable,
             Expression::Lexeme::String,
+            Expression::Lexeme::Null,
             Expression::Lexeme::Equals
           ].freeze
 

lib/gitlab/ci/pipeline/expression/statement.rb

@@ -18,7 +18,7 @@ module Gitlab
             @lexer = Expression::Lexer.new(statement)
 
             @variables = pipeline.variables.map do |variable|
-              { variable.key => variable.value }
+              [variable.key, variable.value]
             end
           end
 
@@ -33,7 +33,7 @@ module Gitlab
           end
 
           def evaluate
-            parse_tree.evaluate(**@variables)
+            parse_tree.evaluate(@variables.to_h)
           end
         end
       end

spec/lib/gitlab/ci/pipeline/expression/statement_spec.rb

@@ -60,4 +60,24 @@ describe Gitlab::Ci::Pipeline::Expression::Statement do
       end
     end
   end
+
+  describe '#evaluate' do
+    statements = [
+      ['$VARIABLE == "my variable"', true],
+      ['"my variable" == $VARIABLE', true],
+      ['$VARIABLE == null', false],
+      ['$VAR == null', true],
+      ['null == $VAR', true],
+      ['$VARIABLE', 'my variable'],
+      ['$VAR', nil],
+    ]
+
+    statements.each do |expression, value|
+      it "evaluates `#{expression}` to `#{value}`" do
+        statement = described_class.new(expression, pipeline)
+
+        expect(statement.evaluate).to eq value
+      end
+    end
+  end
 end