From: "estum (Anton (estum))" <noreply@...>
Date: 2022-09-22T23:18:13+00:00
Subject: [ruby-core:110015] [Ruby master Feature#19015] Language extension by a heredoc

Issue #19015 has been updated by estum (Anton (estum)).


Wow, I am not the only such geek %)
My solution of the similar goal is 7 yo and it'll go to school soon.

```
$ git log lib/osascript.rb
commit 1f39d1d42b499d1424af1fa5a109ecd6ab219563 (HEAD -> master)
Author: Anton
Date:   Thu Jun 11 08:47:12 2015 +0300
```

``` ruby
# @example Simple
#   Osascript.new(<<~SCPT.freeze).()
#     activate application "Finder"
#   SCPT
#
# @example JSC with args
#   # The script takes 2 arguments: directory path & image path
#   # to set a folder icon to the given directory.
#   script = Osascript.new(<<-JS.freeze, lang: 'JavaScript')
#     ObjC.import("Cocoa");
#     function run(input) {
#       var target_path = input[0].toString();
#       var source_image = $.NSImage.alloc.initWithContentsOfFile(input[1].toString());
#       var result = $.NSWorkspace.sharedWorkspace.setIconForFileOptions(source_image, target_path, 0);
#       return target_path;
#     }
#   JS
#   script.(target_dir, folder_icon)
class Osascript
  attr_accessor :script

  def initialize(script = nil, lang: "AppleScript")
    @script = block_given? ? yield : script
    @lang = lang
  end

  def call(*other)
    handle_errors do
      cmd = ["/usr/bin/env", "osascript", *params(*other)]

      IO.popen cmd, "r+", 2 => %i(child out) do |io|
        io.write script
        io.close_write
        io.readlines
      end
    end
  end

  def params(*args)
    ["-l", @lang].tap { |e| e.concat(args.unshift(?-)) unless args.empty? }
  end

  ERROR_PATTERN = /(?<=execution error: )(.+?)(?=$)/
  USER_CANCELLED_PATTERN = /user canceled/i
  NL = "\n"

  private

  def handle_errors
    yield().each_with_object([]) do |line, buf|
      line.match(ERROR_PATTERN) { |m| raise error_for(m[0]), m[0], caller(4) }
      buf << line.strip
    end.join(NL)
  end

  def error_for(msg)
    USER_CANCELLED_PATTERN.test?(msg) ? UserCanceled : ExecutionError
  end

  class ExecutionError < RuntimeError
    CAPTURE_MSG_AND_CODE = /(.+?) \((-?\d+?)\)$/

    attr_reader :code

    def initialize(msg)
      msg.match(CAPTURE_MSG_AND_CODE) { |m| msg, @code, * = m.captures }
      super(msg)
    end
  end

  UserCanceled = Class.new(ExecutionError)
end
```

I've wrote it when I've known that cool syntax hook at the first time ��� an ability to pass only the opening heredoc word in closed parenthesis on single line and you can ducktype it infinitely.

Oh, and I just called in mind one more thing about heredoc: there is some tricky heredoc syntax in core source file `forwardable.rb` which brakes my brain when I try to understand it:

``` ruby
    if _valid_method?(method)
      loc, = caller_locations(2,1)
      pre = "_ ="
      mesg = "#{Module === obj ? obj : obj.class}\##{ali} at #{loc.path}:#{loc.lineno} forwarding to private method "
      method_call = "#{<<-"begin;"}\n#{<<-"end;".chomp}"
        begin;
          unless defined? _.#{method}
            ::Kernel.warn #{mesg.dump}"\#{_.class}"'##{method}', uplevel: 1
            _#{method_call}
          else
            _.#{method}(*args, &block)
          end
        end;
    end

    _compile_method("#{<<-"begin;"}\n#{<<-"end;"}", __FILE__, __LINE__+1)
    begin;
      proc do
        def #{ali}(*args, &block)
          #{pre}
          begin
            #{accessor}
          end#{method_call}
        end
      end
    end;
```

Pretty cryptic, isn't it?

----------------------------------------
Feature #19015: Language extension by a heredoc
https://bugs.ruby-lang.org/issues/19015#change-99266

* Author: ko1 (Koichi Sasada)
* Status: Open
* Priority: Normal
----------------------------------------
This propose new heredoc extension with `<<!LANG` like

```ruby
doc = <<!LANG
  # description written in lang LANG
  foo bar
LANG
```

and it is translated to:

```ruby
doc = heredoc_extension_LANG(heredoc_text, binding)
```

## Example

```ruby
require 'erb'

def heredoc_extension_erb str, b
  ERB.new(str).run(b)
end

name = 'ko1'

html = <<!erb
<div>Hello <%= name %></div>
erb

puts html #=> <div>Hello ko1</div>
```

## Background / considerations

* Sometimes we write Ruby syntax string with `<<RUBY` and this proposal inspired by it.
* it is similar to shebang (`#!LANG` in shell)
* [Elixir's custom sigil](https://elixir-lang.org/getting-started/sigils.html) translates `~u(...)` translates to `sigil_u(...)`. This is why it translated to `heredoc_extension_LANG(...)` private method call.
* JavaScript has JSX but I don't think it is fit to the Ruby language.
* Heredoc is Ruby's chaos part and already confusing a lot. Additional chaos doesn't matter.
* `<<!foo` is valid syntax but now I don't think it is not used. gem codesearch doesn't find the usage.
* Sorry I couldn't wait 1st/Apr.

## Implementation

I attached the experimental implementation which only supports `erb` (because I couldn't find how to get delimiter to determine a method name :p).


---Files--------------------------------
heredoc_extension.patch (2.7 KB)


-- 
https://bugs.ruby-lang.org/

Unsubscribe: <mailto:ruby-core-request@ruby-lang.org?subject=unsubscribe>
<http://lists.ruby-lang.org/cgi-bin/mailman/options/ruby-core>