Remove `ci_if_parenthesis_enabled` feature flag

This removes a feature flag for proven
feature.

config/feature_flags/development/ci_if_parenthesis_enabled.yml

----
-name: ci_if_parenthesis_enabled
-introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/37574
-rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/238174
-group: group::ci
-type: development
-default_enabled: true
\ No newline at end of file

lib/gitlab/ci/features.rb

@@ -39,10 +39,6 @@ module Gitlab
         ::Feature.enabled?(:ci_bulk_insert_on_create, project, default_enabled: true)
       end
 
-      def self.ci_if_parenthesis_enabled?
-        ::Feature.enabled?(:ci_if_parenthesis_enabled, default_enabled: true)
-      end
-
       # NOTE: The feature flag `disallow_to_create_merge_request_pipelines_in_target_project`
       # is a safe switch to disable the feature for a parituclar project when something went wrong,
       # therefore it's not supposed to be enabled by default.

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

@@ -24,26 +24,8 @@ module Gitlab
             Expression::Lexeme::Or
           ].freeze
 
-          # To be removed with `ci_if_parenthesis_enabled`
-          LEGACY_LEXEMES = [
-            Expression::Lexeme::Variable,
-            Expression::Lexeme::String,
-            Expression::Lexeme::Pattern,
-            Expression::Lexeme::Null,
-            Expression::Lexeme::Equals,
-            Expression::Lexeme::Matches,
-            Expression::Lexeme::NotEquals,
-            Expression::Lexeme::NotMatches,
-            Expression::Lexeme::And,
-            Expression::Lexeme::Or
-          ].freeze
-
           def self.lexemes
-            if ::Gitlab::Ci::Features.ci_if_parenthesis_enabled?
-              LEXEMES
-            else
-              LEGACY_LEXEMES
-            end
+            LEXEMES
           end
 
           MAX_TOKENS = 100

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

@@ -15,12 +15,7 @@ module Gitlab
           def tree
             results = []
 
-            tokens =
-              if ::Gitlab::Ci::Features.ci_if_parenthesis_enabled?
-                tokens_rpn
-              else
-                legacy_tokens_rpn
-              end
+            tokens = tokens_rpn
 
             tokens.each do |token|
               case token.type
@@ -78,27 +73,6 @@ module Gitlab
 
             output.concat(operators.reverse)
           end
-
-          # To be removed with `ci_if_parenthesis_enabled`
-          def legacy_tokens_rpn
-            output = []
-            operators = []
-
-            @tokens.each do |token|
-              case token.type
-              when :value
-                output.push(token)
-              when :logical_operator
-                if operators.any? && token.lexeme.precedence >= operators.last.lexeme.precedence
-                  output.push(operators.pop)
-                end
-
-                operators.push(token)
-              end
-            end
-
-            output.concat(operators.reverse)
-          end
         end
       end
     end

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

@@ -90,24 +90,7 @@ RSpec.describe Gitlab::Ci::Pipeline::Expression::Lexer do
         end
 
         with_them do
-          context 'when ci_if_parenthesis_enabled is enabled' do
-            before do
-              stub_feature_flags(ci_if_parenthesis_enabled: true)
-            end
-
-            it { is_expected.to eq(tokens) }
-          end
-
-          context 'when ci_if_parenthesis_enabled is disabled' do
-            before do
-              stub_feature_flags(ci_if_parenthesis_enabled: false)
-            end
-
-            it do
-              expect { subject }
-                .to raise_error described_class::SyntaxError
-            end
-          end
+          it { is_expected.to eq(tokens) }
         end
       end
     end

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

@@ -3,10 +3,6 @@
 require 'spec_helper'
 
 RSpec.describe Gitlab::Ci::Pipeline::Expression::Parser do
-  before do
-    stub_feature_flags(ci_if_parenthesis_enabled: true)
-  end
-
   describe '#tree' do
     context 'validates simple operators' do
       using RSpec::Parameterized::TableSyntax
@@ -31,36 +27,15 @@ RSpec.describe Gitlab::Ci::Pipeline::Expression::Parser do
     context 'when combining && and OR operators' do
       subject { described_class.seed('$VAR1 == "a" || $VAR2 == "b" && $VAR3 == "c" || $VAR4 == "d" && $VAR5 == "e"').tree }
 
-      context 'when parenthesis engine is enabled' do
-        before do
-          stub_feature_flags(ci_if_parenthesis_enabled: true)
-        end
-
-        it 'returns operations in a correct order' do
-          expect(subject.inspect)
-            .to eq('or(or(equals($VAR1, "a"), and(equals($VAR2, "b"), equals($VAR3, "c"))), and(equals($VAR4, "d"), equals($VAR5, "e")))')
-        end
-      end
-
-      context 'when parenthesis engine is disabled (legacy)' do
-        before do
-          stub_feature_flags(ci_if_parenthesis_enabled: false)
-        end
-
-        it 'returns operations in a invalid order' do
-          expect(subject.inspect)
-            .to eq('or(equals($VAR1, "a"), and(equals($VAR2, "b"), or(equals($VAR3, "c"), and(equals($VAR4, "d"), equals($VAR5, "e")))))')
-        end
+      it 'returns operations in a correct order' do
+        expect(subject.inspect)
+          .to eq('or(or(equals($VAR1, "a"), and(equals($VAR2, "b"), equals($VAR3, "c"))), and(equals($VAR4, "d"), equals($VAR5, "e")))')
       end
     end
 
     context 'when using parenthesis' do
       subject { described_class.seed('(($VAR1 == "a" || $VAR2 == "b") && $VAR3 == "c" || $VAR4 == "d") && $VAR5 == "e"').tree }
 
-      before do
-        stub_feature_flags(ci_if_parenthesis_enabled: true)
-      end
-
       it 'returns operations in a correct order' do
         expect(subject.inspect)
           .to eq('and(or(and(or(equals($VAR1, "a"), equals($VAR2, "b")), equals($VAR3, "c")), equals($VAR4, "d")), equals($VAR5, "e"))')
@@ -96,38 +71,21 @@ RSpec.describe Gitlab::Ci::Pipeline::Expression::Parser do
     end
 
     context 'when parenthesis are unmatched' do
-      context 'when parenthesis engine is enabled' do
-        before do
-          stub_feature_flags(ci_if_parenthesis_enabled: true)
-        end
-
-        where(:expression) do
-          [
-            '$VAR == (',
-            '$VAR2 == ("aa"',
-            '$VAR2 == ("aa"))',
-            '$VAR2 == "aa")',
-            '(($VAR2 == "aa")',
-            '($VAR2 == "aa"))'
-          ]
-        end
-
-        with_them do
-          it 'raises a ParseError' do
-            expect { described_class.seed(expression).tree }
-              .to raise_error Gitlab::Ci::Pipeline::Expression::Parser::ParseError
-          end
-        end
+      where(:expression) do
+        [
+          '$VAR == (',
+          '$VAR2 == ("aa"',
+          '$VAR2 == ("aa"))',
+          '$VAR2 == "aa")',
+          '(($VAR2 == "aa")',
+          '($VAR2 == "aa"))'
+        ]
       end
 
-      context 'when parenthesis engine is disabled' do
-        before do
-          stub_feature_flags(ci_if_parenthesis_enabled: false)
-        end
-
-        it 'raises an SyntaxError' do
-          expect { described_class.seed('$VAR == (').tree }
-            .to raise_error Gitlab::Ci::Pipeline::Expression::Lexer::SyntaxError
+      with_them do
+        it 'raises a ParseError' do
+          expect { described_class.seed(expression).tree }
+            .to raise_error Gitlab::Ci::Pipeline::Expression::Parser::ParseError
         end
       end
     end