support Ruby 2.4's frozen string literals (on master)

bin/racc

@@ -165,9 +165,10 @@ def main
     profiler.report
   rescue Racc::CompileError, Errno::ENOENT, Errno::EPERM => err
     raise if $DEBUG
-    lineno   = err.message.slice!(/\A\d+:/).to_s
+    message  = err.message.dup # string may be frozen literal
+    lineno   = message.slice!(/\A\d+:/).to_s
     location = lineno.empty? ? bright("#{input}:") : bright("#{input}:#{lineno}")
-    $stderr.puts "#{red('Error: ')}#{location} #{err.message.strip}"
+    $stderr.puts "#{red('Error: ')}#{location} #{message.strip}"
     exit 1
   end
 end

lib/racc/color.rb

@@ -23,43 +23,43 @@ def self.without_color
     def bright(text)
       return text unless Color.enabled?
       text = text.gsub(/\e\[.*?m[^\e]*\e\[0m/, "\e[0m\\0\e[1m")
-      "\e[1m#{text}\e[0m"
+      String.new "\e[1m#{text}\e[0m"
     end
 
     def red(text)
       return text unless Color.enabled?
-      "\e[31m#{text}\e[0m"
+      String.new "\e[31m#{text}\e[0m"
     end
 
     def green(text)
       return text unless Color.enabled?
-      "\e[32m#{text}\e[0m"
+      String.new "\e[32m#{text}\e[0m"
     end
 
     def violet(text)
       return text unless Color.enabled?
-      "\e[1;35m#{text}\e[0m"
+      String.new "\e[1;35m#{text}\e[0m"
     end
 
     # Syntax highlighting for various types of symbols...
     def nonterminal(text)
       return text unless Color.enabled?
-      "\e[1;34m#{text}\e[0m" # blue
+      String.new "\e[1;34m#{text}\e[0m" # blue
     end
 
     def terminal(text)
       return text unless Color.enabled?
-      "\e[1;36m\e[4m#{text}\e[0m" # cyan, with underline
+      String.new "\e[1;36m\e[4m#{text}\e[0m" # cyan, with underline
     end
 
     def string(text)
       return text unless Color.enabled?
-      "\e[1;33m#{text}\e[0m" # bright yellow
+      String.new "\e[1;33m#{text}\e[0m" # bright yellow
     end
 
     def explicit_prec(text)
       return text unless Color.enabled?
-      "\e[1;31m#{text}\e[0m" # bright reddish orange
+      String.new "\e[1;31m#{text}\e[0m" # bright reddish orange
     end
   end
-end
+end

lib/racc/grammar.rb

@@ -298,7 +298,7 @@ def check_terminals
           locations = undeclared.flat_map(&:locate).map(&:rule).uniq
           raise CompileError, "terminal#{'s' unless undeclared.one?} " \
             "#{Racc.to_sentence(undeclared)} #{undeclared.one? ? 'was' : 'were'} " \
-            "not declared in a 'token' block:\n" <<
+            "not declared in a 'token' block:\n" +
             Source::SparseLines.render(locations.map(&:source))
         end
 
@@ -308,15 +308,15 @@ def check_terminals
           raise CompileError, "token#{'s' unless wrongly_declared.one?} " \
             "#{Racc.to_sentence(wrongly_declared)} were declared in a 'token'" \
             " block, but #{wrongly_declared.one? ? 'it also has' : 'they also have'}" \
-            " derivation rules:\n" << Source::SparseLines.render(bad_rules.map(&:source))
+            " derivation rules:\n" + Source::SparseLines.render(bad_rules.map(&:source))
         end
       end
 
       bad_strings = @symbols.select { |s| s.string_symbol? && s.nonterminal? }
       unless bad_strings.empty?
         bad_rules = bad_strings.flat_map(&:heads).map(&:rule)
         raise CompileError, 'you may not create derivation rules for a ' \
-          "string literal:\n" << Source::SparseLines.render(bad_rules.map(&:source))
+          "string literal:\n" + Source::SparseLines.render(bad_rules.map(&:source))
       end
 
       bad_prec = @symbols.select { |s| s.assoc && s.nonterminal? }
@@ -325,7 +325,7 @@ def check_terminals
         raise CompileError, "token#{'s' unless bad_prec.one?} " \
           "#{Racc.to_sentence(bad_prec)} appeared in a prechigh/preclow " \
           "block, but #{bad_prec.one? ? 'it is not a' : 'they are not'} " \
-          "terminal#{'s' unless bad_prec.one?}:\n" <<
+          "terminal#{'s' unless bad_prec.one?}:\n" +
           Source::SparseLines.render(bad_rules.map(&:source))
       end
 
@@ -335,7 +335,7 @@ def check_terminals
       unless bad_prec.empty?
         raise CompileError, "The following rule#{'s' unless bad_prec.one?} " \
           "use#{'s' if bad_prec.one?} nonterminals for explicit precedence, " \
-          "which is not allowed:\n" <<
+          "which is not allowed:\n" +
           Source::SparseLines.render(bad_prec.map(&:source))
       end
     end
@@ -344,13 +344,13 @@ def check_rules
       @rules.group_by(&:target).each_value do |same_lhs|
         same_lhs.group_by { |r| r.symbols.reject(&:hidden?) }.each_value do |same_rhs|
           next unless same_rhs.size > 1
-          raise CompileError, "The following rules are duplicates:\n" <<
+          raise CompileError, "The following rules are duplicates:\n" +
             Source::SparseLines.render(same_rhs.map(&:source))
         end
       end
 
       unless @error.heads.empty?
-        raise CompileError, "You cannot create rules for the error symbol:\n" <<
+        raise CompileError, "You cannot create rules for the error symbol:\n" +
           Source::SparseLines.render(@error.heads.map { |ptr| ptr.rule.source} )
       end
     end
@@ -568,7 +568,7 @@ def following
     end
 
     def to_s
-      result = "#{@rule.target} : "
+      result = String.new "#{@rule.target} : "
       if @index > 0
         result << "#{preceding.reject(&:hidden?).map(&:to_s).join(' ')} ."
       else

lib/racc/source.rb

@@ -31,7 +31,7 @@ def spiffy
         highlights.sort_by!(&:from)
 
         raw    = text
-        cooked = ''
+        cooked = String.new
         offset = 0
 
         highlights.each do |hilite|

lib/racc/state_transition_table.rb

@@ -202,7 +202,7 @@ def add_entry(all, array, chkval, ptr_array)
     end
 
     def mkmapexp(arr)
-      map = ''
+      map = String.new
       maxdup = RE_DUP_MAX
 
       arr.chunk(&:nil?).each do |is_nil, items|

lib/racc/warning.rb

@@ -53,7 +53,7 @@ def initialize(type, title, details = nil)
     end
 
     def to_s
-      msg = violet('Warning: ') << bright(title)
+      msg = violet('Warning: ') + bright(title)
       msg << "\n" << details if details
       msg
     end
@@ -104,7 +104,7 @@ def title
       def details
         "Its derivation rule#{'s all' unless @sym.heads.one?} contain" \
         "#{'s' if @sym.heads.one?} #{'an ' if @sym.heads.one?}infinite loop" \
-        "#{'s' unless @sym.heads.one?}:\n" <<
+        "#{'s' unless @sym.heads.one?}:\n" +
         @sym.heads.map { |ptr| ptr.rule.to_s }.join("\n")
       end
 
@@ -175,7 +175,7 @@ def details
 
           "When the next token is #{connective}#{Racc.to_sentence(tokens, 'or')}" \
           ", it is overridden by #{rules.one? ? 'this' : 'these'} " \
-          "higher-precedence rule#{'s' unless rules.one?}:\n" <<
+          "higher-precedence rule#{'s' unless rules.one?}:\n" +
           Source::SparseLines.render(rules.map(&:source))
         end.join("\n\n")
       end
@@ -196,15 +196,15 @@ def initialize(conflict, grammar, verbose)
       end
 
       def title
-        "Shift/reduce conflict on #{@sym}," <<
+        "Shift/reduce conflict on #{@sym}," +
           (@path.reject(&:hidden?).empty? ?
             ' at the beginning of the parse.' :
             ' after the following input:')
       end
 
       def details
         if @path.reject(&:hidden?).empty?
-          result = ''
+          result = String.new
         else
           result = @path.reject(&:hidden?).map(&:to_s).join(' ') << "\n"
         end
@@ -253,15 +253,15 @@ def initialize(conflict, grammar, verbose)
       end
 
       def title
-        "Reduce/reduce conflict on #{@sym}," <<
+        "Reduce/reduce conflict on #{@sym}," +
           (@path.reject(&:hidden?).empty? ?
             ' at the beginning of the parse.' :
             ' after the following input:')
       end
 
       def details
         if @path.reject(&:hidden?).empty?
-          result = ''
+          result = String.new
         else
           result = @path.reject(&:hidden?).map(&:to_s).join(' ') << "\n"
         end
@@ -300,4 +300,4 @@ def type
       end
     end
   end
-end
+end

test/run_tests.sh

@@ -1,4 +1,14 @@
 #!/usr/bin/env bash
 
+set -eux
+
+test_frozen_strings=$(ruby -e 'puts (RUBY_ENGINE == "ruby" && RUBY_VERSION > "2.4")')
+
+if [[ $test_frozen_strings == "true" ]] ; then
+  echo "NOTE: enabling frozen string literals"
+  rvm install rubygems 2.6.12 --force # because of an issue in rubygems 2.7 with ruby 2.5 and frozen string literals
+  export RUBYOPT="--enable-frozen-string-literal --debug=frozen-string-literal"
+fi
+
 bundle exec rake test
 bundle exec rake test_pure

test/test_scanner.rb

@@ -9,11 +9,11 @@ class TestScanner < TestCase
       define_method("test_scan_#{File.basename(testfile)}".to_sym) do
         original = File.read(testfile)
         # wrap the Ruby source code in an action block
-        wrapped  = "class Test\nrule\na : '*' {" << original << "\n}"
+        wrapped  = "class Test\nrule\na : '*' {" + original + "\n}"
         file     = Source::Buffer.new(testfile, wrapped)
         scanner  = Racc::GrammarFileScanner.new(file)
 
-        rebuilt = ''
+        rebuilt = String.new
         scanner.yylex do |token|
           break if token.nil?
           rebuilt << token[1][0].text if token[0] == :ACTION