Annotate syntax error without require

Currently dead_end works by monkey patching require. This causes confusion and problems as other tools are not expecting this. For example zombocom/derailed_benchmarks#204 and #124. This PR utilizes the new SyntaxError#detailed_message as introduced in ruby/ruby#5516 that will be released in Ruby 3.2.

That means that developers using dead_end with Ruby 3.2+ will experience more consistent behavior.


## Limitations

As pointed out in #31 the current version of dead_end only works if the developer requires dead_end and then invokes `require`.

This behavior is still not fixed for Ruby 3.2+ 

```
$ ruby -v
ruby 3.2.0preview1 (2022-04-03 master f801386f0c) [x86_64-darwin20]
$ cat monkeypatch.rb
  SyntaxError.prepend Module.new {
    def detailed_message(highlight: nil, **)
      message = super
      message += "Monkeypatch worked\n"
      message
    end
  }

  # require_relative "bad.rb"
  # Note that i am commenting
  # out the require, but leaving
  # in the monkeypatch
⛄️ 3.2.0 🚀 /tmp
$ cat bad.rb
  def lol_i-am-a-synt^xerror
⛄️ 3.2.0 🚀 /tmp
$ ruby -r./monkeypatch.rb bad.rb
bad.rb:1: syntax error, unexpected '-', expecting ';' or '\n'
  def lol_i-am-a-synt^xerror
```

Additionally we are still not able to handle the case where a program is streamed to ruby and does not exist on disk:

```
$ echo "def foo" | ruby
```

As the SyntaxError does not provide us with the contents of the script.

```
$ echo "def foo" | ruby
-:1: syntax error, unexpected end-of-input
def foo
```

CHANGELOG.md

@@ -1,5 +1,7 @@
 ## HEAD (unreleased)
 
+- Support Ruby 3.2 integration with SyntaxError (https://github.com/zombocom/dead_end/pull/139)
+
 ## 3.1.2
 
 - Fixed internal class AroundBlockScan, minor changes in outputs (https://github.com/zombocom/dead_end/pull/131)

lib/dead_end/core_ext.rb

@@ -1,35 +1,83 @@
 # frozen_string_literal: true
 
-# Monkey patch kernel to ensure that all `require` calls call the same
-# method
-module Kernel
-  module_function
-
-  alias_method :dead_end_original_require, :require
-  alias_method :dead_end_original_require_relative, :require_relative
-  alias_method :dead_end_original_load, :load
-
-  def load(file, wrap = false)
-    dead_end_original_load(file)
-  rescue SyntaxError => e
-    DeadEnd.handle_error(e)
-  end
+# Ruby 3.2+ has a cleaner way to hook into Ruby that doesn't use `require`
+if SyntaxError.new.respond_to?(:detailed_message)
+  module DeadEnd
+    class MiniStringIO
+      def initialize(isatty: $stderr.isatty)
+        @string = +""
+        @isatty = isatty
+      end
+
+      attr_reader :isatty
 
-  def require(file)
-    dead_end_original_require(file)
-  rescue SyntaxError => e
-    DeadEnd.handle_error(e)
+      def puts(value = $/, **)
+        @string << value
+      end
+
+      attr_reader :string
+    end
   end
 
-  def require_relative(file)
-    if Pathname.new(file).absolute?
-      dead_end_original_require file
-    else
-      relative_from = caller_locations(1..1).first
-      relative_from_path = relative_from.absolute_path || relative_from.path
-      dead_end_original_require File.expand_path("../#{file}", relative_from_path)
+  SyntaxError.prepend Module.new {
+    def detailed_message(highlight: nil, **)
+      message = super
+      file = DeadEnd::PathnameFromMessage.new(message).call.name
+      io = DeadEnd::MiniStringIO.new
+
+      if file
+        DeadEnd.call(
+          io: io,
+          source: file.read,
+          filename: file
+        )
+        annotation = io.string
+
+        annotation + message
+      else
+        message
+      end
+    rescue => e
+      if ENV["DEBUG"]
+        $stderr.warn(e.message)
+        $stderr.warn(e.backtrace)
+      end
+
+      raise e
+    end
+  }
+else
+  # Monkey patch kernel to ensure that all `require` calls call the same
+  # method
+  module Kernel
+    module_function
+
+    alias_method :dead_end_original_require, :require
+    alias_method :dead_end_original_require_relative, :require_relative
+    alias_method :dead_end_original_load, :load
+
+    def load(file, wrap = false)
+      dead_end_original_load(file)
+    rescue SyntaxError => e
+      DeadEnd.handle_error(e)
+    end
+
+    def require(file)
+      dead_end_original_require(file)
+    rescue SyntaxError => e
+      DeadEnd.handle_error(e)
+    end
+
+    def require_relative(file)
+      if Pathname.new(file).absolute?
+        dead_end_original_require file
+      else
+        relative_from = caller_locations(1..1).first
+        relative_from_path = relative_from.absolute_path || relative_from.path
+        dead_end_original_require File.expand_path("../#{file}", relative_from_path)
+      end
+    rescue SyntaxError => e
+      DeadEnd.handle_error(e)
     end
-  rescue SyntaxError => e
-    DeadEnd.handle_error(e)
   end
 end

spec/integration/ruby_command_line_spec.rb

@@ -36,7 +36,9 @@ module DeadEnd
         end
 
         methods = (dead_end_methods_array - kernel_methods_array).sort
-        expect(methods).to eq(["dead_end_original_load", "dead_end_original_require", "dead_end_original_require_relative"])
+        if methods.any?
+          expect(methods).to eq(["dead_end_original_load", "dead_end_original_require", "dead_end_original_require_relative"])
+        end
 
         methods = (api_only_methods_array - kernel_methods_array).sort
         expect(methods).to eq([])
@@ -71,5 +73,33 @@ module DeadEnd
         expect(out).to include('❯  5    it "flerg"').once
       end
     end
+
+    it "annotates a syntax error in Ruby 3.2+ when require is not used" do
+      pending("Support for SyntaxError#detailed_message monkeypatch needed https://gist.github.com/schneems/09f45cc23b9a8c46e9af6acbb6e6840d?permalink_comment_id=4172585#gistcomment-4172585")
+
+      skip if Gem::Version.new(RUBY_VERSION) < Gem::Version.new("3.2")
+
+      Dir.mktmpdir do |dir|
+        tmpdir = Pathname(dir)
+        script = tmpdir.join("script.rb")
+        script.write <<~EOM
+          describe "things" do
+            it "blerg" do
+            end
+
+            it "flerg"
+            end
+
+            it "zlerg" do
+            end
+          end
+        EOM
+
+        out = `ruby -I#{lib_dir} -rdead_end #{script} 2>&1`
+
+        expect($?.success?).to be_falsey
+        expect(out).to include('❯  5    it "flerg"').once
+      end
+    end
   end
 end