ERB, ancient and future

ERB, ancient and future [email protected] Beyond Journey's End

About me Masatoshi Seki Ruby Core Committer (dRuby, Rinda, ERB)
toRuby / Tochigi Ruby Meetup Pokémon TCG, WCS 2010 Tochigi Pref. winner 2

toRuby / Tochigi Ruby Meetup Pokémon TCG, WCS 2010 Tochigi Pref. winner 40年くらいプログラマだよ 3

toRuby / Tochigi Ruby Meetup Pokémon TCG, WCS 2010 Tochigi Pref. winner Complex embedded systems with concurrency and GUI 4 Gallstones

toRuby / Tochigi Ruby Meetup Pokémon TCG, WCS 2010 Tochigi Pref. winner I wrote them in 1999-2000 5

toRuby / Tochigi Ruby Meetup Pokémon TCG, WCS 2010 Tochigi Pref. winner I wrote them in 1999-2000 6

toRuby / Tochigi Ruby Meetup Pokémon TCG, WCS 2010 Tochigi Pref. winner 7 Makoto Inoue Web Developer @ New Bamboo (UK) Translator of “The dRuby Book” Rails is A Follower what we can learn from dRuby’s metaprogramming magic Masatoshi SEKI Makoto Inoue

toRuby / Tochigi Ruby Meetup Pokémon TCG, WCS 2010 Tochigi Pref. winner 8 Big Bird. (scaling twitter) Rinda • Shared Queue (TupleSpace) • Built with DRb • RingyDingy makes it stupid easy • See Eric Hodel’s documentation • O(N) for take(). Sigh.

toRuby / Tochigi Ruby Meetup Pokémon TCG, WCS 2010 Tochigi Pref. winner 9

toRuby / Tochigi Ruby Meetup Pokémon TCG, WCS 2010 Tochigi Pref. winner 第205回toRubyは2024-06-05 10 情報デザインのロゴ

toRuby / Tochigi Ruby Meetup Pokémon TCG, WCS 2010 Tochigi Pref. winner RubyKaigi 2022, 2023 11

12 https://www.pokemon-card.com/ex/sv4/

13 https://tcg.pokemon.com/en-us/expansions/paradox-rift/

Agenda ERB conjecture Rails-compatible ERB 14

Ancient ERB conjecture ERB予想 15 1999

Before ERB When I posted a template engine that replaces
&entity;, Shugo told me about his plans for eRuby. ruby-dev:5286 (1999-02-19) Re: htmlelem.rb (Re: HTML generator) 16 1999

eRuby specs ePerlの影響を強くうけているみたいだぞ 17 print ≒ <%= .. %> !?
I'm not the one implementing it (Tsundere) ePerl! ? Shugo CEO was a part-time worker at the time. 1999

ePerl !? e is for embedded. 文書にPerlが埋め込まれてる感じみたい 18 <? ...
!> !? mod_perl !!! 1999

I'll write it embedding control structures 😊 CGI-oriented 😭 CGIに寄せすぎでは？
19 1999

Hello, World. 20 Hello, World. print "Hello, World.\n"

Hello, World. 21 <p> <% print "Hello, World!" %> <%=
"Hello, World! %> </p> print "<p>\n" print "Hello, World!" print "Hello, World!" print "</p>\n"

control structure 22 <ul> <% ENV.each do |row| %> <li><%=
row[0] %></li> <% end %> </ul> print "<ul>\n" ENV.each do |row| print "<li>"; print row[0]; print "</li>\n" end print "</ul>\n"

Remember CGI? $stdout → HTTP response CGI・おぼえていますか 23 puts %Q{Content-Type:
text/html} puts puts %Q{<!DOCTYPE html>} puts %Q{<html lang="ja">} puts %Q{<head>} puts %Q{</head>} puts %Q{<body>} puts %Q{<ul>} ENV.each do |row| puts %Q!<li>#{row[0]}</li>! end puts %Q{</ul>} puts %Q{</body>} puts %Q{</html>} Content-Type: text/html <!DOCTYPE html> <html lang="ja"> <head> </head> <body> <ul> <li>TERM_PROGRAM</li> ... </ul> </body> </html>

Remember CGI? $stdout → HTTP response CGI・おぼえていますか 24 puts %Q{Content-Type:
text/html} puts puts %Q{<!DOCTYPE html>} puts %Q{<html lang="ja">} puts %Q{<head>} puts %Q{</head>} puts %Q{<body>} puts %Q{<ul>} ENV.each do |row| puts %Q!<li>#{row[0]}</li>! end puts %Q{</ul>} puts %Q{</body>} puts %Q{</html>} Content-Type: text/html <!DOCTYPE html> <html lang="ja"> <head> </head> <body> <ul> <li>TERM_PROGRAM</li> ... </ul> </body> </html> puts puts puts

Rewrite puts to eRuby Stringの式展開では制御構造が書きにくい（書ける？）のだがeRubyならかんたん 25 puts %Q{<!DOCTYPE html>} puts
%Q{<html lang="ja">} puts %Q{<head>} puts %Q{</head>} puts %Q{<body>} puts %Q{<ul>} ENV.each do |row| puts %Q!<li>#{row[0]}</li>! end puts %Q{</ul>} puts %Q{</body>} puts %Q{</html>} <!DOCTYPE html> <html lang="ja"> <head> </head> <body> <ul> <% ENV.each do |row| %> <li><%= row[0] %></li> <% end %> </ul> </body> </html>

This specification is not good CGI programming style will change
in the near future Page generation becomes more complex Will change to something more server-like 26 1999

becomes more complex Part of the page will be generated
by a method Helper? 27 <h2>report hoge</h2> <ul> <% result.each do |row| %> <li><%= format_date(row.date) %></li> <% end %> </ul> def format_date(date) date.strftime("%Y-%m-%d") end ERB conjecture 1999

becomes more complex nest common header, navigation, footer and content
標準出力に出すよりも連結した方がよいのでは？ 28 ERB conjecture <%= header %> <%= navi %> <%= content %> <%= footer %> 1999

CGI programming model will change A long-lived server is required
due to preprocessing costs and information exchange between requests. e.g. dRuby + ERB Concurrency and $stdout will conflict 29 ERB conjecture 1999

ERb and ERbLight ERb - eRuby's spec, like a command
ERbLight - eRuby w/o $stdout, String concatenation a library, build the page using String instead of puts() Support writing Ruby applications using eRuby notation 30 1999

Ruby x 256 book Legendary hacker explains the power of
this specification 2001, ASCII たださんとartonさんがeRuby/dRubyを絶賛するすごい本 31 2001

renamed ERbLight to ERB And ERB was included in Ruby's
standard library. ERb is obsolete ERb is obsolete 32 2003

25 years have passed almost correct ! ERB-inspired libraries make
me happy Merb, Rails... 自分用のライブラリは自分で書いてるけど、そういうものがあるのはうれしい 33 2024 ERB conjecture

Usage ERB.new, ERB#result 34 >> ERB.new('Hello World').result => "Hello World"
>> ERB.new('1 + 1 = <%= 1 + 1 %>').result => "1 + 1 = 2"

ERB#src Translate eRuby to Ruby _erboutという変数に結果を連結する 35 <ul> <% list.each
do |row| %> <li><%= row %></li> <% end %> </ul> >> puts erb.src #coding:UTF-8 _erbout = +''; _erbout.<< "<ul>\n".freeze ; list.each do |row| ; _erbout.<< "\n<li>".freeze ; _erbout.<<(( row ).to_s); _erbout.<< "</li>\n".freeze ; end ; _erbout.<< "\n</ul>\n".freeze ; _erbout

ERB#result with binding binding 36 <ul> <% list.each do |row|
%> <li><%= row %></li> <% end %> </ul> >> erb = ERB.new(erb_src) >> list = [1, 'two', 3.0] >> erb.result(binding) => "<ul>\n\n<li>1</ li>\n\n<li>two</li>\n\n<li>3.0</ li>\n\n</ul>\n"

ERB#def_method def_method(mod, methodname, fname='(ERB)') 37 class Foo def initialize(arg) @list
= arg end ERB.new(<<EOS).def_method(self, 'bar') <ul> <% @list.each do |row| %> <li><%= row %></li> <% end %> </ul> EOS end Foo#bar instance var unpopular features

ERB#def_method Avoid parsing the source multiple times Compose with small
template objects Used only in Ikezawa's products 38 unpopular features

Proc in template Case study: Create a survey page with
similar questions repeatedly Each question has a large table with an answer column Element IDs and form names must be unique Write in one template ↑矢板市北部で一番Herokuを使ってる「情報デザイン」のロゴ 39 Q A Q A Q A Q A Q A

Actual survey page

Each question has an answer sheet... !?

Each cell has detailed answer tables 10MB HTML

Proc in template 43 <% t = Proc.new do |arg|
%> <h3>Answer column for <%= arg %></h3> <table id="table-<%= arg %>"> ... </table> <% end %> <h3>Question 1</h3> this is the first question <% t.call("q1") %> <h3>Question 2</h3> That's the second question <% t.call("q2") %> <h3>Question 1</h3> this is the first question <h3>Answer column for q1</h3> <table id="table-q1"> ... </table> <h3>Question 2</h3> That's the second question <h3>Answer column for q2</h3> <table id="table-q2"> ... </table> call

Proc in template いやなことを思い出した 44 <% t = Proc.new do
|arg| %> <h3>Answer column for <%= arg %></h3> <table id="table-<%= arg %>"> ... </table> <% end %> <h3>Question 1</h3> this is the first question <% t.call("q1") %> <h3>Question 2</h3> That's the second question <% t.call("q2") %> <h3>Question 1</h3> this is the first question <h3>Answer column for q1</h3> <table id="table-q1"> ... </table> <h3>Question 2</h3> That's the second question <h3>Answer column for q2</h3> <table id="table-q2"> ... </table> call

Future Rails-compatible ERB 45

RubyConf 2014 https://speakerdeck.com/a_matsuda/template-engines-in-ruby 46 2014

I tried やりましょう 47 I noticed this 2 years ago,
! And asked Seki-san if we could extend ERB to be "Rails compatible" before Ruby 2.0 release 2012

and gave up できませんでした 48 But gave up. ! Because
he didn't like this part in ActionView + Erubis ! BLOCK_EXPR = /\s+(do|\{)(\s*\|[^|]*\|)?\s*\Z/ ! This code scans the template with the Regexp and detects the Ruby block, but this kind of code could be imperfect ! So this is not acceptable as an ERB spec, said Seki- san.

Railsに正規表現でブロックの開始を検知して処理を切り替えるコードがあった 49 That is why this syntax is not acceptable
in ERB <%= form_for @article do |f| %> ... <% end %>

Maybe it's solved I noticed this while writing the slides
for RWC2023. https://gist.github.com/seki/610a42932a85209aaa33547ae983bbdf 50 2023

<%= ... %> to_s 51 <%= 1i ** 0.5 %>
#coding:UTF-8 _erbout = +''; _erbout.<<(( 1i ** 0.5 ).to_s); _erbout.<< "\n".freeze ; _erbout

<%= ... %> with block ブロック付きメソッドを <%= ... %>に置くのが難しい 52
<%= form_with do %> ... <% end %>

<%= ... %> with block こうなっちゃう 53 <%= form_with do
%> ... <% end %> #coding:UTF-8 _erbout = +''; _erbout.<<(( form_with do ).to_s); _erbout.<< "\n ... \n".freeze ; end ; _erbout.<< "\n".freeze ; _erbout

(( ... ).to_s) ((...).to_s)の括弧がじゃまなのでバッファクラスへ移動すればよい？ 54 <%= form_with do %> ...
<% end %> #coding:UTF-8 _erbout = +''; _erbout.<<(( form_with do ).to_s); _erbout.<< "\n ... \n".freeze ; end ; _erbout.<< "\n".freeze ; _erbout

Customizable Rubyへの変換方法はカスタマイズできる 55 <%= form_with do %> ... <% end
%> #coding:UTF-8 _erbout = +''; _erbout.<<(( form_with do ).to_s); _erbout.<< "\n ... \n".freeze ; end ; _erbout.<< "\n".freeze ; _erbout

Ruby is difficult Rubyむずかしい 56 _erbout << h("str") # OK
_erbout << h "str" # SyntaxError <<と括弧なしのメソッド呼び出し

_erbout << h "str" # SyntaxError _erbout.concat h "str" # OK but .... _erbout.concat form_with "arg" do |arg| # NG ... # end # concatʹϒϩοΫ͕౉Δ <<と括弧なしのメソッド呼び出し <<でなくふつうのメソッド呼び出しにしてもこのブロックはconcatのブロック引数になる

_erbout << h "str" # SyntaxError _erbout = h "str" # _erbout = form_with "arg" do |arg| # ... end _erbout.concat h "str" # OK but .... _erbout.concat form_with "arg" do |arg| # NG ... # end # concatʹϒϩοΫ͕౉Δ 代入なら大丈夫なのに... <<と括弧なしのメソッド呼び出し <<でなくふつうのメソッド呼び出しにしてもこのブロックはconcatのブロック引数になる

Addition Asignment += works fine 代入しながらメソッド呼べばよい? 59 _erbout += h
"str" # OK _erbout += form_with "arg" do |arg| # OK ... end

ERBOut result buffer 60 class ERBOut Buffer = String #
SafeBuffer if rails def initialize(s='') @str = Buffer.new(s) end def to_s @str end def <<(other) @str << other end def +(other) @str << other.to_s self end def capture(*arg, &block) save = @str @str = Buffer.new yield(*arg) return @str ensure @str = save end end

ERBOut result buffer 61 class ERBOut Buffer = String #
SafeBuffer if rails def initialize(s='') @str = Buffer.new(s) end def to_s @str end def <<(other) @str << other end def +(other) @str << other.to_s self end def capture(*arg, &block) save = @str @str = Buffer.new yield(*arg) return @str ensure @str = save end end

ERBOut result buffer many tricks + 62 class ERBOut Buffer
= String # SafeBuffer if rails def initialize(s='') @str = Buffer.new(s) end def to_s @str end def <<(other) @str << other end def +(other) @str << other.to_s self end def capture(*arg, &block) save = @str @str = Buffer.new yield(*arg) return @str ensure @str = save end end normalize and concatenate return itself

ERBOut result buffer many tricks + capture 63 class ERBOut
Buffer = String # SafeBuffer if rails def initialize(s='') @str = Buffer.new(s) end def to_s @str end def <<(other) @str << other end def +(other) @str << other.to_s self end def capture(*arg, &block) save = @str @str = Buffer.new yield(*arg) return @str ensure @str = save end end save restore call block and capture

なんかできちゃった 64 <%= form_with do %> ... <% end %>
#coding:UTF-8 _erbout = ERB::ERBOut.new; _erbout += form_with do ; _erbout << "\n ...\n".freeze ; end ; _erbout << "\n".freeze ; _erbout.to_s result buffer addition assignment

capture ブロックのローカル変数をさわってcaptureのしかけを呼び出す 65 def capture(*arg, &block) block.binding.local_variable_get(:_erbout).capture(*arg, &block) end <%
it = capture do %> ... <% end %> このブロックのbinding local var :_erbout of block

I want someone to make it work in a Rails
environment. I made no progress since last year 進捗ダメです 66

Agenda ERB conjecture Rails-compatible ERB 67

One more thing ... 68

One more thing ... 69

ERB, ancient and future

ERB, ancient and future

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