Add a base class for pipeline expressions tokens

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

@@ -2,7 +2,7 @@ module Gitlab
   module Ci
     module Pipeline
       module Expression
-        class Equality
+        class Equality  < Expression::Token
           PATTERN = /==/.freeze
 
           def initialize(left, right)

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

@@ -2,7 +2,7 @@ module Gitlab
   module Ci
     module Pipeline
       module Expression
-        class String
+        class String < Expression::Token
           PATTERN = /("|')(?<value>.+)('|")/.freeze
 
           def initialize(value)

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

+module Gitlab
+  module Ci
+    module Pipeline
+      module Expression
+        class Token
+          def evaluate(**variables)
+            raise NotImplementedError
+          end
+
+          def self.build(string)
+            raise NotImplementedError
+          end
+
+          def self.scan(scanner)
+            scanner.scan(PATTERN)
+          end
+        end
+      end
+    end
+  end
+end

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

@@ -2,7 +2,7 @@ module Gitlab
   module Ci
     module Pipeline
       module Expression
-        class Equality
+        class Equality < Expression::Token
           PATTERN = /$(?<name>\w+)/.freeze
 
           def initialize(value)