Add a base class for pipeline expressions tokens

4 files changed, 24 insertions, 3 deletions

diff --git a/lib/gitlab/ci/pipeline/expression/equality.rb b/lib/gitlab/ci/pipeline/expression/equality.rb
index dd2cf0118f2..668b581df5a 100644
--- a/lib/gitlab/ci/pipeline/expression/equality.rb
+++ b/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)
diff --git a/lib/gitlab/ci/pipeline/expression/string.rb b/lib/gitlab/ci/pipeline/expression/string.rb
index 6a4d78a67a1..d8d6155f431 100644
--- a/lib/gitlab/ci/pipeline/expression/string.rb
+++ b/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)
diff --git a/lib/gitlab/ci/pipeline/expression/token.rb b/lib/gitlab/ci/pipeline/expression/token.rb
new file mode 100644
index 00000000000..bf28191a645
--- /dev/null
+++ b/lib/gitlab/ci/pipeline/expression/token.rb
@@ -0,0 +1,21 @@
+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
diff --git a/lib/gitlab/ci/pipeline/expression/variable.rb b/lib/gitlab/ci/pipeline/expression/variable.rb
index e547a9aaa46..d22566c61a8 100644
--- a/lib/gitlab/ci/pipeline/expression/variable.rb
+++ b/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)