From 26167c24f6f82e7586a03ecbfa9979a74825585d Mon Sep 17 00:00:00 2001
From: Grzegorz Bizon <grzesiek.bizon@gmail.com>
Date: Thu, 1 Mar 2018 12:16:58 +0100
Subject: Improve pipeline expressions lexer

---
 lib/gitlab/ci/pipeline/expression/lexer.rb         | 42 ++++++++++++++--------
 .../gitlab/ci/pipeline/expression/lexer_spec.rb    |  4 +--
 2 files changed, 29 insertions(+), 17 deletions(-)

diff --git a/lib/gitlab/ci/pipeline/expression/lexer.rb b/lib/gitlab/ci/pipeline/expression/lexer.rb
index 067ad5fd312..cabb91d0dd7 100644
--- a/lib/gitlab/ci/pipeline/expression/lexer.rb
+++ b/lib/gitlab/ci/pipeline/expression/lexer.rb
@@ -3,6 +3,8 @@ module Gitlab
     module Pipeline
       module Expression
         class Lexer
+          include ::Gitlab::Utils::StrongMemoize
+
           LEXEMES = [
             Expression::Lexeme::Variable,
             Expression::Lexeme::String,
@@ -10,34 +12,44 @@ module Gitlab
             Expression::Lexeme::Equals
           ].freeze
 
-          MAX_CYCLES = 5
           SyntaxError = Class.new(Statement::StatementError)
 
+          MAX_TOKENS = 100
+
           def initialize(statement)
             @scanner = StringScanner.new(statement)
-            @tokens = []
           end
 
-          def tokens
-            return @tokens if @tokens.any?
+          def tokens(max: MAX_TOKENS)
+            strong_memoize(:tokens) { tokenize(max) }
+          end
+
+          def lexemes
+            tokens.map(&:to_lexeme)
+          end
+
+          private
 
-            MAX_CYCLES.times do
-              LEXEMES.each do |lexeme|
-                @scanner.skip(/\s+/) # ignore whitespace
+          def tokenize(max_tokens)
+            tokens = []
 
-                lexeme.scan(@scanner).tap do |token|
-                  @tokens.push(token) if token.present?
+            max_tokens.times do
+              @scanner.skip(/\s+/) # ignore whitespace
+
+              return tokens if @scanner.eos?
+
+              lexeme = LEXEMES.find do |type|
+                type.scan(@scanner).tap do |token|
+                  tokens.push(token) if token.present?
                 end
+              end
 
-                return @tokens if @scanner.eos?
+              unless lexeme.present?
+                raise Lexer::SyntaxError, 'Unknown lexeme found!'
               end
             end
 
-            raise Lexer::SyntaxError unless @scanner.eos?
-          end
-
-          def lexemes
-            tokens.map(&:to_lexeme)
+            raise Lexer::SyntaxError, 'Too many tokens!'
           end
         end
       end
diff --git a/spec/lib/gitlab/ci/pipeline/expression/lexer_spec.rb b/spec/lib/gitlab/ci/pipeline/expression/lexer_spec.rb
index 0d70ca6c906..65f90b0caf3 100644
--- a/spec/lib/gitlab/ci/pipeline/expression/lexer_spec.rb
+++ b/spec/lib/gitlab/ci/pipeline/expression/lexer_spec.rb
@@ -45,10 +45,10 @@ describe Gitlab::Ci::Pipeline::Expression::Lexer do
       expect(tokens.third.value).to eq '"text"'
     end
 
-    it 'limits statement to 5 tokens' do
+    it 'limits statement to specified amount of tokens' do
       lexer = described_class.new("$V1 $V2 $V3 $V4 $V5 $V6")
 
-      expect { lexer.tokens }
+      expect { lexer.tokens(max: 5) }
         .to raise_error described_class::SyntaxError
     end
 
-- 
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