Auto merge of #4143 - deepj:string-frozen-literal, r=indirect

[WIP] Better support of Ruby 2.3 with enabled frozen string literal

This commit prevents several bugs with `RuntimeError: can't modify frozen String` with enabled string frozen literal in Ruby 2.3

10 files changed, 23 insertions, 12 deletions

diff --git a/.rubocop.yml b/.rubocop.yml
index adf2867b00..ea89254c7d 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -63,6 +63,10 @@ Style/TrailingComma:
 Style/TrailingUnderscoreVariable:
   Enabled: false
 
+# `String.new` is preferred style with enabled frozen string literal
+Style/EmptyLiteral:
+  Enabled: false
+
 # 1.8.7 support
 
 Style/HashSyntax:
diff --git a/.travis.yml b/.travis.yml
index c7d6deb873..357403e762 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -91,6 +91,11 @@ matrix:
     # Ruby-head (we want to know how we're doing, but not fail the build)
     - rvm: ruby-head
       env: RGV=master
+    # Ruby-head with enabled frozen string literal
+    - rvm: ruby-head
+      env:
+        - RGV=master
+        - RUBYOPT="--enable-frozen-string-literal --debug=frozen-string-literal"
   allow_failures:
     - rvm: 1.8.7
       env: RGV=v2.1.11
diff --git a/lib/bundler/definition.rb b/lib/bundler/definition.rb
index 2729ca75b0..deb6af5cbb 100644
--- a/lib/bundler/definition.rb
+++ b/lib/bundler/definition.rb
@@ -53,7 +53,7 @@ module Bundler
       @specs           = nil
       @ruby_version    = ruby_version
 
-      @lockfile_contents      = ""
+      @lockfile_contents      = String.new
       @locked_bundler_version = nil
 
       if lockfile && File.exist?(lockfile)
@@ -298,7 +298,7 @@ module Bundler
     end
 
     def to_lock
-      out = ""
+      out = String.new
 
       sources.lock_sources.each do |source|
         # Add the source header
diff --git a/lib/bundler/env.rb b/lib/bundler/env.rb
index 6942eccaa8..93d35900ae 100644
--- a/lib/bundler/env.rb
+++ b/lib/bundler/env.rb
@@ -11,7 +11,7 @@ module Bundler
       print_gemfile = options.delete(:print_gemfile)
       print_gemspecs = options.delete(:print_gemspecs)
 
-      out = "Environment\n\n"
+      out = String.new("Environment\n\n")
       out << "    Bundler   #{Bundler::VERSION}\n"
       out << "    Rubygems  #{Gem::VERSION}\n"
       out << "    Ruby      #{ruby_version}"
@@ -62,7 +62,7 @@ module Bundler
     end
 
     def ruby_version
-      str = "#{RUBY_VERSION}"
+      str = String.new("#{RUBY_VERSION}")
       if RUBY_VERSION < "1.9"
         str << " (#{RUBY_RELEASE_DATE}"
         str << " patchlevel #{RUBY_PATCHLEVEL}" if defined? RUBY_PATCHLEVEL
diff --git a/lib/bundler/gem_helper.rb b/lib/bundler/gem_helper.rb
index 99d4194edf..8cfbeb4df1 100644
--- a/lib/bundler/gem_helper.rb
+++ b/lib/bundler/gem_helper.rb
@@ -173,7 +173,7 @@ module Bundler
 
     def sh_with_code(cmd, &block)
       cmd << " 2>&1"
-      outbuf = ""
+      outbuf = String.new
       Bundler.ui.debug(cmd)
       SharedHelpers.chdir(base) do
         outbuf = `#{cmd}`
diff --git a/lib/bundler/lazy_specification.rb b/lib/bundler/lazy_specification.rb
index 38ab0a16c6..b3d0d4e732 100644
--- a/lib/bundler/lazy_specification.rb
+++ b/lib/bundler/lazy_specification.rb
@@ -35,10 +35,12 @@ module Bundler
     end
 
     def to_lock
+      out = String.new
+
       if platform == Gem::Platform::RUBY || platform.nil?
-        out = "    #{name} (#{version})\n"
+        out << "    #{name} (#{version})\n"
       else
-        out = "    #{name} (#{version}-#{platform})\n"
+        out << "    #{name} (#{version}-#{platform})\n"
       end
 
       dependencies.sort_by(&:to_s).uniq.each do |dep|
diff --git a/lib/bundler/resolver.rb b/lib/bundler/resolver.rb
index a798705aa7..82dcd7fbfd 100644
--- a/lib/bundler/resolver.rb
+++ b/lib/bundler/resolver.rb
@@ -21,7 +21,7 @@ module Bundler
           end
           o << %(  In Gemfile:\n)
           o << conflict.requirement_trees.sort_by {|t| t.reverse.map(&:name) }.map do |tree|
-            t = ""
+            t = String.new
             depth = 2
             tree.each do |req|
               t << "  " * depth << req.to_s
diff --git a/lib/bundler/rubygems_ext.rb b/lib/bundler/rubygems_ext.rb
index 33f6308014..e1051a3851 100644
--- a/lib/bundler/rubygems_ext.rb
+++ b/lib/bundler/rubygems_ext.rb
@@ -94,7 +94,7 @@ module Gem
   private
 
     def dependencies_to_gemfile(dependencies, group = nil)
-      gemfile = ""
+      gemfile = String.new
       if dependencies.any?
         gemfile << "group :#{group} do\n" if group
         dependencies.each do |dependency|
@@ -126,7 +126,7 @@ module Gem
     end
 
     def to_lock
-      out = "  #{name}"
+      out = String.new("  #{name}")
       unless requirement == Gem::Requirement.default
         reqs = requirement.requirements.map {|o, v| "#{o} #{v}" }.sort.reverse
         out << " (#{reqs.join(", ")})"
diff --git a/lib/bundler/source/path.rb b/lib/bundler/source/path.rb
index 4192015cb7..ebdab3e813 100644
--- a/lib/bundler/source/path.rb
+++ b/lib/bundler/source/path.rb
@@ -42,7 +42,7 @@ module Bundler
       end
 
       def to_lock
-        out = "PATH\n"
+        out = String.new("PATH\n")
         out << "  remote: #{relative_path}\n"
         out << "  glob: #{@glob}\n" unless @glob == DEFAULT_GLOB
         out << "  specs:\n"
diff --git a/lib/bundler/source/rubygems.rb b/lib/bundler/source/rubygems.rb
index 1f45888421..effd4680f6 100644
--- a/lib/bundler/source/rubygems.rb
+++ b/lib/bundler/source/rubygems.rb
@@ -60,7 +60,7 @@ module Bundler
       end
 
       def to_lock
-        out = "GEM\n"
+        out = String.new("GEM\n")
         remotes.reverse_each do |remote|
           out << "  remote: #{suppress_configured_credentials remote}\n"
         end