Drop Ruby 2.3 support.

Ref: #402
Ref: https://bugs.ruby-lang.org/issues/10222
Ref: ruby/ruby@5754f15
Ref: ruby/ruby@b6d3927

Up to Ruby 2.3, `require` would resolve symlinks, but `require_relative` wouldn't:

```ruby
require 'fileutils'
FileUtils.mkdir_p("realpath")
File.write("realpath/a.rb", "p :a_loaded")
File.symlink("realpath", "symlink") rescue nil

$LOAD_PATH.unshift(File.realpath(__dir__) + "/symlink")
require "a.rb" # load symlink/a.rb in 2.3 and older, load realpath/a.rb on 2.4 and newer
require_relative "realpath/a.rb" # noop on 2.4+
```

This would easily cause double loading issue when `require` and `require_relative`
were mixed, but was fixed in 2.4 (https://bugs.ruby-lang.org/issues/10222).

The problem is that `Bootsnap` kinda negated this fix, because `realpath()`
wouldn't be applied to absolute paths:

```ruby
require 'fileutils'
FileUtils.mkdir_p("realpath")
File.write("realpath/a.rb", "p :a_loaded")
File.symlink("realpath", "symlink") rescue nil

$LOAD_PATH.unshift(File.realpath(__dir__) + "/symlink")
require File.expand_path("symlink/a.rb") # load symlink/a.rb in 3.0 and older, load realpath/a.rb on 3.1 and newer
require_relative "realpath/a.rb" # noop on 3.1+
```

And for performance reasons, Bootsnap tried really hard not to call `realpath`,
as it's a syscall, instead it used `expand_path`, which is entirely in use
space and doesn't reach to the file system. So if you had a `symlink` in
`$LOAD_PATH`, `bootcsnap` would perpetuate this bug, which led to the
addition of #136.

This was ultimately fixed in Ruby 3.1 (https://bugs.ruby-lang.org/issues/17885),
now `realpath` is applied even on absolute paths.

While `realpath` is indeed expensive, I think the performance impact is ok if
we only call it for `$LOAD_PATH` members, rather than for all requirable files.
So if you have X gems, it's going to be more or less X `realpath` calls.

It would stay a problem if a gem actually contained symlinks and used
`require_relative`, but it's quite the stretch, and with 3.1 now
handling it, it's not worth keeping such workaround.

See: #402

.github/workflows/ci.yaml

@@ -32,15 +32,15 @@ jobs:
       - uses: actions/checkout@v2
       - uses: ruby/setup-ruby@v1
         with:
-          ruby-version: '2.3'
+          ruby-version: '2.4'
           bundler-cache: true
       - run: bundle exec rubocop
 
   rubies:
     strategy:
       matrix:
         os: [ubuntu]
-        ruby: ['2.3', '2.4', '2.5', '2.6', '2.7', '3.0', '3.1', 'ruby-head', 'debug']
+        ruby: ['2.4', '2.5', '2.6', '2.7', '3.0', '3.1', 'ruby-head', 'debug']
     runs-on: ${{ matrix.os }}-latest
     steps:
       - uses: actions/checkout@v2

.rubocop.yml

@@ -2,38 +2,17 @@ AllCops:
   Exclude:
     - 'vendor/**/*'
     - 'tmp/**/*'
-  TargetRubyVersion: 2.3
+  TargetRubyVersion: 2.4
 
-# This doesn't take into account retrying from an exception
-Lint/SuppressedException:
-  Enabled: false
-
-# allow String.new to create mutable strings
-Style/EmptyLiteral:
-  Enabled: false
-
-Style/EmptyMethod:
+Bundler/OrderedGems:
   Enabled: false
 
-# allow the use of globals which makes sense in a CLI app like this
-Style/GlobalVars:
+Gemspec/OrderedDependencies:
   Enabled: false
 
-Style/PercentLiteralDelimiters:
+Gemspec/DuplicatedAssignment:
   Enabled: false
 
-Style/TrailingCommaInHashLiteral:
-  EnforcedStyleForMultiline: comma
-
-Style/TrailingCommaInArrayLiteral:
-  EnforcedStyleForMultiline: comma
-
-Style/TrailingCommaInArguments:
-  EnforcedStyleForMultiline: comma
-
-Layout/LineLength:
-  Max: 120
-
 Metrics/AbcSize:
   Enabled: false
 
@@ -65,33 +44,12 @@ Naming/MethodName:
 Naming/RescuedExceptionsVariableName:
   PreferredName: error
 
-Bundler/OrderedGems:
-  Enabled: false
-
-Gemspec/OrderedDependencies:
-  Enabled: false
-
-Gemspec/DuplicatedAssignment:
+Naming/VariableNumber:
   Enabled: false
 
 Layout/MultilineMethodCallIndentation:
   EnforcedStyle: indented
 
-Style/SymbolArray:
-  Enabled: false
-
-Style/StderrPuts:
-  Enabled: false
-
-Style/ModuleFunction:
-  Enabled: false
-
-Style/IfUnlessModifier:
-  Enabled: false
-
-Style/GuardClause:
-  Enabled: false
-
 Layout/EndAlignment:
   EnforcedStyleAlignWith: start_of_line
 
@@ -101,24 +59,78 @@ Layout/RescueEnsureAlignment:
 Layout/FirstHashElementIndentation:
   EnforcedStyle: consistent
 
-Style/NumericPredicate:
-  Enabled: false
-
 Layout/SpaceInsideHashLiteralBraces:
   EnforcedStyle: no_space
 
+Layout/SpaceAroundMethodCallOperator:
+  Enabled: true
+
+Layout/LineLength:
+  Max: 120
+
+# This doesn't take into account retrying from an exception
+Lint/SuppressedException:
+  Enabled: false
+
 Lint/AssignmentInCondition:
   AllowSafeAssignment: true
 
 Lint/UnusedMethodArgument:
   AllowUnusedKeywordArguments: true
 
+Lint/RaiseException:
+  Enabled: true
+
+Lint/StructNewOverride:
+  Enabled: true
+
 Security/MarshalLoad:
   Enabled: false
 
 Security/YAMLLoad:
   Enabled: false
 
+# allow String.new to create mutable strings
+Style/EmptyLiteral:
+  Enabled: false
+
+Style/EmptyMethod:
+  Enabled: false
+
+# allow the use of globals which makes sense in a CLI app like this
+Style/GlobalVars:
+  Enabled: false
+
+Style/PercentLiteralDelimiters:
+  Enabled: false
+
+Style/TrailingCommaInHashLiteral:
+  EnforcedStyleForMultiline: comma
+
+Style/TrailingCommaInArrayLiteral:
+  EnforcedStyleForMultiline: comma
+
+Style/TrailingCommaInArguments:
+  EnforcedStyleForMultiline: comma
+
+Style/SymbolArray:
+  Enabled: false
+
+Style/StderrPuts:
+  Enabled: false
+
+Style/ModuleFunction:
+  Enabled: false
+
+Style/IfUnlessModifier:
+  Enabled: false
+
+Style/GuardClause:
+  Enabled: false
+
+Style/NumericPredicate:
+  Enabled: false
+
 Style/Alias:
   EnforcedStyle: prefer_alias_method
 
@@ -131,22 +143,12 @@ Style/DoubleNegation:
 Style/CommentedKeyword:
   Enabled: false
 
-Naming/VariableNumber:
-  Enabled: false
-
 Style/Next:
   Enabled: false
 
 Style/StringLiterals:
   EnforcedStyle: double_quotes
 
-
-Lint/RaiseException:
-  Enabled: true
-
-Lint/StructNewOverride:
-  Enabled: true
-
 Style/HashEachMethods:
   Enabled: true
 
@@ -161,3 +163,6 @@ Style/RedundantReturn:
 
 Style/YodaCondition:
   Enabled: false
+
+Style/ExponentialNotation:
+  Enabled: true

CHANGELOG.md

@@ -1,5 +1,7 @@
 # Unreleased
 
+* Drop support for Ruby 2.3. 
+
 # 1.10.3
 
 * Fix Regexp and Date type support in YAML compile cache. (#400)

Gemfile

@@ -16,6 +16,6 @@ gem "minitest", "~> 5.0"
 gem "mocha", "~> 1.2"
 
 group :development do
-  gem "rubocop", "0.81.0" # Ruby 2.3 support
+  gem "rubocop", "0.82.0" # Ruby 2.4 support
   gem "byebug", platform: :ruby
 end

bootsnap.gemspec

@@ -29,7 +29,7 @@ Gem::Specification.new do |spec|
   spec.bindir        = "exe"
   spec.executables   = %w(bootsnap)
 
-  spec.required_ruby_version = ">= 2.3.0"
+  spec.required_ruby_version = ">= 2.4.0"
 
   if RUBY_PLATFORM =~ /java/
     spec.platform = "java"

lib/bootsnap/compile_cache.rb

@@ -50,9 +50,7 @@ def self.permission_error(path)
 
     def self.supported?
       # only enable on 'ruby' (MRI), POSIX (darwin, linux, *bsd), Windows (RubyInstaller2) and >= 2.3.0
-      RUBY_ENGINE == "ruby" &&
-        RUBY_PLATFORM =~ /darwin|linux|bsd|mswin|mingw|cygwin/ &&
-        Gem::Version.new(RUBY_VERSION) >= Gem::Version.new("2.3.0")
+      RUBY_ENGINE == "ruby" && RUBY_PLATFORM.match?(/darwin|linux|bsd|mswin|mingw|cygwin/)
     end
   end
 end

test/compile_cache_key_format_test.rb

@@ -49,14 +49,14 @@ def test_key_ruby_revision
   def test_key_size
     key = cache_key_for_file(FILE)
     exp = File.size(FILE)
-    act = key[R[:size]].unpack("Q")[0]
+    act = key[R[:size]].unpack1("Q")
     assert_equal(exp, act)
   end
 
   def test_key_mtime
     key = cache_key_for_file(FILE)
     exp = File.mtime(FILE).to_i
-    act = key[R[:mtime]].unpack("Q")[0]
+    act = key[R[:mtime]].unpack1("Q")
     assert_equal(exp, act)
   end