Feature #19015
openLanguage extension by a heredoc
Description
This propose new heredoc extension with <<!LANG
like
doc = <<!LANG
# description written in lang LANG
foo bar
LANG
and it is translated to:
doc = heredoc_extension_LANG(heredoc_text, binding)
Example¶
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 translates
~u(...)
translates tosigil_u(...)
. This is why it translated toheredoc_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
Updated by ko1 (Koichi Sasada) about 2 years ago
- File deleted (
tmp.YubJ1EHi0O-xyzzy)
Updated by ko1 (Koichi Sasada) about 2 years ago
- File heredoc_extension.patch heredoc_extension.patch added
Updated by ko1 (Koichi Sasada) about 2 years ago
Related I heard:
- Template literals (Template strings) - JavaScript | MDN Tagged templates
Updated by retro (Josef Šimánek) about 2 years ago
Would you mind to add also what's the output to the description? If I understand it well, following will be printed.
<div>Hello ko1</div>
Any plans already what to do when method is not implemented?
Updated by zverok (Victor Shepelev) about 2 years ago
I am not sure how serious this is (considering the "Apr 1" notice), but I have somewhat adjacent thought:
In many modern code editors, highlighting of several different languages in the same file is supported. Namely, SublimeText (I am not sure about the others, but I suppose the idea is not unique) understands this:
query = <<~SQL
SELECT * FROM users WHERE status='active
SQL
DB.execute(query)
...and highlights the code inside a heredoc as SQL.
I am thinking that maybe some way of preserving the "tag" it was surrounded (in String metadata?.. Or, making HEREDOC-produced object a different class, a descendant of String with extra functionality) would be generically useful. It will allow implementing the @ko1 (Koichi Sasada) 's example just like this:
require 'erb'
def heredoc_extension_erb str, b
ERB.new(str).run(b)
end
name = 'ko1'
html = <<~erb
<div>Hello <%= name %></div>
erb
puts execute_heredoc(html, binding)
# where...
def execute_heredoc(str, binding)
case str.__tag__
when 'erb'
ERB.new(str).run(binding)
# ....
end
end
The idea can even be expanded to provide additional metadata (currently invalid syntax, so no compatibility would be broken):
html = <<~erb(trim_mode="%>")
<div>Hello <%= name %></div>
erb
WDYT?
Updated by yugui (Yuki Sonoda) about 2 years ago
one bikeshedding..
Usually syntax-suger in Ruby are mapped into methods whose names are very consistent with the syntax. e.g. `
, []=
, or foo=
. Therefore, it is more consistent to map the new syntax into <<!LANG
method.
It seems possible to make the lexer distinguish such a notation from <<
symbol.
Updated by ko1 (Koichi Sasada) about 2 years ago
This is a tiny example of SQL.
Note that I'm newbe of SQL (I goooooooogled the syntax/api and the example is never tested).
module SQLite3HeredocExtension
def compile str
vs = []
compiled = str.gsub(/\?([a-z_][a-zA-Z\d]+)/){|m|
vs << $1
??
}
[vs, compiled]
end
# syntax
# * SQL statement
# * but ?var is replaced with the Ruby's variable
def heredoc_exntesion_SQL str, b
vs, compiled_str = compile str
stmt = @db.prepare compiled_str
@db.execute stmt, vs.map{|v| b.local_variable_get(v).to_s}
end
end
require 'sqlite3'
@db = SQLite3::Database.new "test.db"
include SQLite3HeredocExtension
results = <<!SQL
select person.name from people where person.age > ?lowest_age
SQL
## hmm, "SQL" seems to return a SQL statement...?
# AR
results = People.select(:name).where("age >= ?", lowest_age)
# AR/execute
results = ActiveRecord::Base.connection.execute("select person.name from perople where person.age > ?", lowest_age)
Updated by estum (Anton (estum)) about 2 years ago
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
# @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.match?(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:
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?
Updated by duerst (Martin Dürst) about 2 years ago
This proposal sounds interesting, but the naming looks like behind-the-scenes metaprogramming; it may be better to use a more flexible approach that doesn't fix the function name.
Updated by Eregon (Benoit Daloze) about 2 years ago
This seems nice.
Would it also remove leading indentation like <<~HEREDOC
?
Updated by ko1 (Koichi Sasada) about 2 years ago
Would it also remove leading indentation like <<~HEREDOC?
Sure.
Updated by dsisnero (Dominic Sisneros) about 2 years ago
It reminds me of javascript template literals and tagged templates. Instead of passing in bindings they pass the interpolation points and the first argument is an array containing thestring split at interpolation points, and the second is the interplation values.
require 'cgi'
def heredoc_extension_erb strs_separated_array_at, **interpolation_points
result = strs_separated_array.zip(interpolation_points).each_with_object([]) do |s, v, ar|
ar << s
ar << v if v
end
result.join(" ")
end
name = 'ko1'
html = <<!html
<div class="#{clsname}">Hello #{name}</div>
erb
I could see where this could be used to provide cmd interpolation similar to julia
files = ["/etc/password", "/Volumes/External HD/data.csv"]
def heredoc_ext_cmd(strs_ar, values)
# shellescape values -
# if current_values is a array and curr_str ends in space and next str is nonexistant or ends in space join values with a space
#
#collect cmd and cmd_args
result = Process.new(cmd, cmd_args)
end
mycmd = <<!cmd
grep foo #{files}
cmd
mycmd.run
Updated by pyromaniac (Arkadiy Zabazhanov) over 1 year ago
Hey folks. I'm actually wondering, why don't support Elixir-like sigils in Ruby? We have a ton of them already: %w[]
, %r//
, so why don't just add a support for custom ones?
I'm, for once, tired of writing Date.new
or Time.parse
, I'd like to have it %D[2023-05-05]
or Money gem can introduce something like %M(100 USD)
instead of the long Money.from_amount(100, "USD")
version.
Updated by duerst (Martin Dürst) over 1 year ago
@pyromaniac (Arkadiy Zabazhanov) I think the main problem would be how to handle namespacing. With single letters, the chance of collision is very high. How does Elixir handle this?
Updated by pyromaniac (Arkadiy Zabazhanov) over 1 year ago
@duerst (Martin Dürst) It is funny you asked cause I just found this
[Kernel] Support for multi-letter uppercase sigils
here https://hexdocs.pm/elixir/main/changelog.html
We can definitely start doing this right from the beginning.
Also, from my experience, even 1-letter sigils are not causing any issues but simplifying code reading/writing a lot.
Sigils are going especially improve the readability in specs where you need to initialize a lot of VO/DTO literals.