Enabled frozen string literals (#1154)

* Enabled frozen string literals

* Update rubocop config

* Prefer string interpolation in simple cases

Co-Authored-By: Dylan Thacker-Smith <[email protected]>

test/integration/assign_test.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'test_helper'
 
 class AssignTest < Minitest::Test

test/integration/blank_test.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'test_helper'
 
 class FoobarTag < Liquid::Tag

test/integration/block_test.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'test_helper'
 
 class BlockTest < Minitest::Test

test/integration/capture_test.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'test_helper'
 
 class CaptureTest < Minitest::Test

test/integration/context_test.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'test_helper'
 
 class ContextTest < Minitest::Test

test/integration/document_test.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'test_helper'
 
 class DocumentTest < Minitest::Test

test/integration/drop_test.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'test_helper'
 
 class ContextDrop < Liquid::Drop
@@ -31,7 +33,7 @@ class ProductDrop < Liquid::Drop
 
   class CatchallDrop < Liquid::Drop
     def liquid_method_missing(method)
-      'catchall_method: ' << method.to_s
+      "catchall_method: #{method}"
     end
   end
 
@@ -48,7 +50,7 @@ class ProductDrop < Liquid::Drop
   end
 
   def user_input
-    "foo".taint
+    (+"foo").taint
   end
 
   protected

test/integration/error_handling_test.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'test_helper'
 
 class ErrorHandlingTest < Minitest::Test

test/integration/filter_test.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'test_helper'
 
 module MoneyFilter

test/integration/hash_ordering_test.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'test_helper'
 
 class HashOrderingTest < Minitest::Test

test/integration/output_test.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'test_helper'
 
 module FunnyFilter

test/integration/parsing_quirks_test.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'test_helper'
 
 class ParsingQuirksTest < Minitest::Test

test/integration/render_profiling_test.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'test_helper'
 
 class RenderProfilingTest < Minitest::Test

test/integration/security_test.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'test_helper'
 
 module SecurityFilter

test/integration/standard_filter_test.rb

@@ -1,4 +1,5 @@
 # encoding: utf-8
+# frozen_string_literal: true
 
 require 'test_helper'
 

test/integration/tags/break_tag_test.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'test_helper'
 
 class BreakTagTest < Minitest::Test

test/integration/tags/continue_tag_test.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'test_helper'
 
 class ContinueTagTest < Minitest::Test

test/integration/tags/echo_test.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'test_helper'
 
 class EchoTest < Minitest::Test

test/integration/tags/for_tag_test.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'test_helper'
 
 class ThingWithValue < Liquid::Drop

test/integration/tags/if_else_tag_test.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'test_helper'
 
 class IfElseTagTest < Minitest::Test

test/integration/tags/include_tag_test.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'test_helper'
 
 class TestFileSystem

test/integration/tags/increment_tag_test.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'test_helper'
 
 class IncrementTagTest < Minitest::Test

test/integration/tags/liquid_tag_test.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'test_helper'
 
 class LiquidTagTest < Minitest::Test

test/integration/tags/raw_tag_test.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'test_helper'
 
 class RawTagTest < Minitest::Test

test/integration/tags/render_tag_test.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'test_helper'
 
 class RenderTagTest < Minitest::Test

test/integration/tags/standard_tag_test.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'test_helper'
 
 class StandardTagTest < Minitest::Test

test/integration/tags/statements_test.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'test_helper'
 
 class StatementsTest < Minitest::Test

test/integration/tags/table_row_test.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'test_helper'
 
 class TableRowTest < Minitest::Test

test/integration/tags/unless_else_tag_test.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'test_helper'
 
 class UnlessElseTagTest < Minitest::Test

test/integration/template_test.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'test_helper'
 require 'timeout'
 

test/integration/trim_mode_test.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'test_helper'
 
 class TrimModeTest < Minitest::Test

test/integration/variable_test.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'test_helper'
 
 class VariableTest < Minitest::Test

test/test_helper.rb

@@ -1,4 +1,5 @@
 #!/usr/bin/env ruby
+# frozen_string_literal: true
 
 ENV["MT_NO_EXPECTATIONS"] = "1"
 require 'minitest/autorun'

test/unit/block_unit_test.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'test_helper'
 
 class BlockUnitTest < Minitest::Test
@@ -61,7 +63,7 @@ class BlockUnitTest < Minitest::Test
 
       assert_equal 'hello', template.render
 
-      buf = ''
+      buf = +''
       output = template.render({}, output: buf)
       assert_equal 'hello', output
       assert_equal 'hello', buf
@@ -79,7 +81,7 @@ class BlockUnitTest < Minitest::Test
 
       assert_equal 'foohellobar', template.render
 
-      buf = ''
+      buf = +''
       output = template.render({}, output: buf)
       assert_equal 'foohellobar', output
       assert_equal 'foohellobar', buf

test/unit/condition_unit_test.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'test_helper'
 
 class ConditionUnitTest < Minitest::Test

test/unit/context_unit_test.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'test_helper'
 
 class HundredCentes

test/unit/file_system_unit_test.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'test_helper'
 
 class FileSystemUnitTest < Minitest::Test

test/unit/i18n_unit_test.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'test_helper'
 
 class I18nUnitTest < Minitest::Test

test/unit/lexer_unit_test.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'test_helper'
 
 class LexerUnitTest < Minitest::Test

test/unit/parser_unit_test.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'test_helper'
 
 class ParserUnitTest < Minitest::Test

test/unit/partial_cache_unit_test.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'test_helper'
 
 class PartialCacheUnitTest < Minitest::Test

test/unit/regexp_unit_test.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'test_helper'
 
 class RegexpUnitTest < Minitest::Test

test/unit/strainer_unit_test.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'test_helper'
 
 class StrainerUnitTest < Minitest::Test

test/unit/tag_unit_test.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'test_helper'
 
 class TagUnitTest < Minitest::Test
@@ -31,7 +33,7 @@ class TagUnitTest < Minitest::Test
 
       assert_equal 'hello', template.render
 
-      buf = ''
+      buf = +''
       output = template.render({}, output: buf)
       assert_equal 'hello', output
       assert_equal 'hello', buf
@@ -49,7 +51,7 @@ class TagUnitTest < Minitest::Test
 
       assert_equal 'foohellobar', template.render
 
-      buf = ''
+      buf = +''
       output = template.render({}, output: buf)
       assert_equal 'foohellobar', output
       assert_equal 'foohellobar', buf

test/unit/tags/case_tag_unit_test.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'test_helper'
 
 class CaseTagUnitTest < Minitest::Test

test/unit/tags/for_tag_unit_test.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'test_helper'
 
 class ForTagUnitTest < Minitest::Test

test/unit/tags/if_tag_unit_test.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'test_helper'
 
 class IfTagUnitTest < Minitest::Test

test/unit/template_unit_test.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'test_helper'
 
 class TemplateUnitTest < Minitest::Test

test/unit/tokenizer_unit_test.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'test_helper'
 
 class TokenizerTest < Minitest::Test

test/unit/variable_unit_test.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'test_helper'
 
 class VariableUnitTest < Minitest::Test