Writing DSLs with Parslet - Wicked Good Ruby Conf

Watch it online: http://confreaks.com/videos/2730-wickedgoodruby-writing-dsl-s-with-parslet

A well-designed DSL improves programmer productivity and communication with domain experts. The Ruby community has produced a number of very popular external DSLs--Coffeescript, HAML, SASS, and Cucumber to name a few.

Parslet makes it easy to write these kinds of DSLs in pure Ruby. In this talk you’ll learn the basics, feel out the limitations of several approaches and find some common solutions. In no time, you’ll have the power to make a great new DSL, slurp in obscure file formats, modify or fork other people’s grammars (like Gherkin, TOML, or JSON), or even write your own programming language!

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Hello, everyone. I’m Jason Garber and I’m a software engineer and co-founder at PromptWorks in Philadelphia. We’re a Ruby and Javascript development consultancy and the three principals have been working with Ruby since 2005.
We practice test-driven development, we test all the effing time (cheers, Bryan), and all the other things that make us buzzword-compliant.

It's a great place to work and we have a fantastic team. You should ask us about our pairing setup. It’s awesome.

The Ruby community is thriving in Philadelphia; We’ve doubled in size in the past year. We love having speakers and guests from other cities, so please come. The view from the 45th floor where we have our meetups is spectacular.

This talk is about...

Transcript

1. Writing DSLs with Parslet Jason Garber W i c k e d G o o d R u b y C o n f
4. TDD
5. TDD TATFT
6. TDD TATFT Agile! Scrum Pair Programming VIM Pomodoro Continuous Integration Continuous Delivery
8. Parsing
9. DSLS Domain-Specific Languages
11. <?xml version="1.0"?> <configuration><configSections><sectionGr oup name="userSettings" type="System.Configuration.UserSettings Group, System, Version=2.0.0.0, Culture=neutral, PublicKeyToken =b77a5c561934e089"><section name="MSDNSampleSettings.My.MySetti ngs" type="System.Configuration.ClientSettingsSection, System, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e0 89" allowExeDefinition="MachineToLocalUser" requirePermission=" false"/></sectionGroup></configSections> ... <userSettings><MSD NSampleSettings.My.MySettings><setting name="Setting" serialize As="String"><value>SomeDefaultValue</value></setting></MSDNSamp leSettings.My.MySettings></userSettings> </configuration>
12. </xml>
13. I DSLs
14. RssReader::Application.routes.draw do devise_for :users resources :feeds, only: [:edit, :update, :show, :index] post '/feeds', to: 'feeds#create', as: 'create_feed' resources :users do get 'page/:page', action: :index, on: :collection end resources :posts do member do put :update_category end end get '/my_profile', to: 'users#my_profile', as: :my_profile root to: "home#home" end
15. describe Stack do context "stack with one item" do let(:stack) { a_stack_with_one_item } context "when popped" do before { stack.pop } it { should be_empty } end end end
16. click_on "Sign Up" fill_in "Email", with: account[:email] fill_in "Password", with: account[:password] fill_in "Confirmation", with: account[:password_confirmation] fill_in "Name", with: account[:name] select account[:birthyear].to_s, from: "Year born" check "Terms" click_on "I'm ready to join!" current_path.should eq "/accounts/#{account.id}/dashboard" page.should have_content "Dashboard"
17. desc 'Generate markup and stylesheets and open browser preview' task :preview => FileList['*.html'] + FileList['*.css'] do |t| sh 'open -g index.html' end rule '.html' => '.haml' do |t| puts "Rebuilding #{t.name}" sh "haml #{t.source} #{t.name}" end rule '.css' => lambda { |cssfile| source(cssfile) } do |t| puts "Rebuilding #{t.name}" sh "sass #{t.source} #{t.name}" end
18. get '/' do @posts = Post.all(:order => [:id.desc], :limit => 20) erb :index end get '/post/new' do erb :new end get '/post/:id' do @post = Post.get(params[:id]) erb :post end post '/post/create' do post = Post.new(params) status 201 redirect "/post/#{post.id}" end
19. rule(:table) do (str("table") >> attributes?.as(:attributes) >> str(".\n")).maybe >> table_row.repeat(1).as(:content) >> block_end end rule(:table_row) do table_row_attributes >> table_row_content >> end_table_row end rule(:table_row_attributes) { (attributes?.as(:attributes) >> str(". ")).maybe } rule(:table_row_content) { (table_header | table_data).repeat(1).as(:content) } rule(:end_table_row) { str("|") >> (block_end.present? | (str("\n"))) } rule(:table_header) do str("|_. ") >> table_content.as(:content) end rule(:table_data) do str("|") >> str("\n").absent? >> td_attributes? >> table_content.as(:content) end
20. Internal DSLs Fluent Interfaces
21. EXTERNAL DSLS
22. upstream puma { server unix:///tmp/sockets/puma.sock fail_timeout=0; } server { listen 80 default deferred; server_name promptworks.com www.promptworks.com; root /srv/promptworks/public; charset utf-8; if (-f $document_root/system/maintenance.html) { return 503; } error_page 503 @maintenance; location @maintenance { rewrite ^(.*)$ /system/maintenance.html last; break; } }
23. <([A-Z][A-Z0-9]*)\b[^>]*>(.*?)<\/\1> \b(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3} (?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\b
24. SELECT DISTINCT sc1.id FROM ( SELECT DATE_ADD(entry_point.start_date, INTERVAL (digits_1.digit * 10 + d (1 << (DAYOFWEEK(DATE_ADD(entry_point.start_date, INTERVAL (digits_1.digi FROM (SELECT CAST('2012-03-01' AS date) AS start_date) AS entry_point INNER JOIN (SELECT 0 AS digit UNION SELECT 1 UNION SELECT 2 UNION SELECT ON (digits_1.digit * 10 + digits_2.digit) <= (DATEDIFF(DATE_ADD(entry_poi ) AS md INNER JOIN schedules AS sc1 INNER JOIN negative_link_influences AS neg on (sc1.call_type_id = neg.call_type_id or neg.call_type_id = -1) WHERE sc1.schedule_on = md.date AND neg.affected_shift = 0;
25. BEGIN { TOTAL=0 } { TOTAL = TOTAL + $1 } END { print TOTAL/NR } {print "<li><a href=\"" $1 "\">" $1 "</a></li>"}
26. ! doctype html html head title Test body - unless items.empty? ol - items.each do |item| li = item - else p No items
27. Feature: Searching music As a User I want to be able to search music So I can play it Background: Given I am logged in Scenario: Search music Given I am on the search screen When I search for "mix" Then I should see the mixtape
28. class erlang { file { "/etc/apt/sources.list.d/esl-erlang.list": ensure => present, owner => root, content => 'deb http://example.com/debian precise contrib'; } exec { "apt-update": command => "/usr/bin/apt-get update", refreshonly => true; } package { "esl-erlang": ensure => installed, require => Exec['apt-update', 'import-key']; } } include erlang
29. Heroku buildpack: Ruby ====================== This is a [Heroku buildpack](http://devcenter.heroku.com/article It uses [Bundler](http://gembundler.com) for dependency manageme Usage ----- ### Ruby Example Usage: $ heroku create --stack cedar --buildpack https://github.com $ git push heroku master
30. title = "T??? Example" [owner] name = "Tom Preston-Werner" organization = "GitHub" bio = "GitHub Cofounder & CEO\nLikes tater tots and beer." dob = 1979-05-27T07:32:00Z # First class dates? Why not? [database] server = "192.168.1.1" ports = [ 8001, 8001, 8002 ] connection_max = 5000 enabled = true
31. global= { \time 4/4 \key c \major \tempo "Allegro" 4 = 132 \set Score.skipBars = ##t } Violinone = \new Voice { \relative c''{ \set Staff.midiInstrument = #"violin" \set tupletSpannerDuration = #(ly:make-moment 1 4) % Jason solo R1 * 9 r2 r4 \times 2/3 { c4( b8)
32. gsave 1 0.5 scale 70 100 48 0 360 arc fill grestore /Helvetica-Bold 14 selectfont 1.0 setgray 29 45 moveto (Hello, world!) show showpage
33. .accordion { li { border-top: 1px solid #e2e4e6; &:first-child { border-top-color: transparent; } } a { @include rem(padding, 5px 10px 6px); &.icon { padding-left: 40px; position: relative; } &.icon img { @include rem(left, 10px); margin-top: -2px; position: absolute; } } }
36. h1. Give Textile a try! A *simple* paragraph with a line break, some _emphasis_ and a "link":http://redcloth.org * an item * and another # one # two # three
37. h1. Give Textile a try! A *simple* paragraph with a line break, some _emphasis_ and a "link":http://redcloth.org * an item * and another # one # two # three
39. A_HLGN = /(?:\<(?!>)|\<\>|\=|[()]+)/ A_VLGN = /[\-^~]/ C_CLAS = '(?:\([^)]+\))' C_LNGE = '(?:\[[^\]]+\])' C_STYL = '(?:\{[^}]+\})' S_CSPN = '(?:\\\\\d+)' S_RSPN = '(?:/\d+)' A = "(?:#{A_HLGN}?#{A_VLGN}?|#{A_VLGN}?#{A_HLGN}?)" S = "(?:#{S_CSPN}?#{S_RSPN}|#{S_RSPN}?#{S_CSPN}?)" C = "(?:#{C_CLAS}?#{C_STYL}?#{C_LNGE}?|#{C_STYL}? #{C_LNGE}?#{C_CLAS}?|#{C_LNGE}?#{C_STYL}?#{C_CLAS}?)" PUNCT = Regexp::quote( '!"#$%&\'*+,-./:;=?@\\^_`|~' ) HYPERLINK = '(\S+?)([^\w\s/;=\?]*?)(\s|$)'
40. def links( text ) text.gsub!( / ([\s\[{(]|[#{PUNCT}])? # $pre " # start (#{C}) # $atts ([^"]+?) # $text \s? (?:\(([^)]+?)\)(?="))? # $title ": (\S+?) # $url (\/)? # $slash ([^\w\/;]*?) # $post (?=\s|\.[#{PUNCT}]+|$) /x ) do |m| pre,atts,text,title,url,slash,post = $~[1..7] url = check_refs( url ) atts = pba( atts ) atts << " title=\"#{ title }\"" if title atts = shelve( atts ) if atts "#{ pre }<a href=\"#{ url }#{ slash }\"#{ atts }>" + "#{ text }</a>#{ post }" end end
41. “Some people, when confronted with a problem, think ‘I know, I'll use regular expressions.’ Now they have two problems.” — Jamie Zawinski
43. %%{ machine superredcloth_scan; include superredcloth_common "ext/superredcloth_scan/superredcloth_common.rl"; action extend { extend = rb_hash_aref(regs, ID2SYM(rb_intern("type"))); } # blocks notextile_tag_start = "<notextile>" ; notextile_tag_end = "</notextile>" CRLF? ; notextile_block_start = ( "notextile" >A %{ STORE(type) } A C :> "." ( "." %extend | "" ) " "+ ) ; pre_tag_start = "<pre" [^>]* ">" (space* "<code>")? ; pre_tag_end = ("</code>" space*)? "</pre>" CRLF? ; pre_block_start = ( "pre" >A %{ STORE(type) } A C :> "." ( "." %extend | "" ) " "+ ) ; bc_start = ( "bc" >A %{ STORE(type) } A C :> "." ( "." %extend | "" ) " "+ ) ; btype = ( "p" | "h1"... block_start = ( btype >A %{ STORE(type) } A C :> "." ( "." %extend | "" ) " "+ ) ; next_block_start = ( btype A C :> "."+ " " ) >A @{ p = reg - 1; } ; pre_tag := |* pre_tag_end { CAT(block); DONE(block); fgoto main; }; default => esc_pre; *|; notextile_tag := |* notextile_tag_end { DONE(block); fgoto main; }; default => cat; *|; }%%
44. void rb_str_cat_escaped(VALUE str, char *ts, char *te, unsigned int opts); void rb_str_cat_escaped_for_preformatted(VALUE str, char *ts, char *te, unsigned int opts); VALUE superredcloth_inline(VALUE, char *, char *, VALUE); VALUE superredcloth_inline2(VALUE, VALUE, VALUE); #define CAT(H) rb_str_cat(H, ts, te-ts) #define CLEAR(H) H = rb_str_new2("") #define INLINE(H, T) rb_str_append(H, rb_funcall(rb_formatter, rb_intern(#T), 1, regs)) VALUE superredcloth_transform(rb_formatter, p, pe, refs) VALUE rb_formatter; char *p, *pe; VALUE refs; { if (RSTRING(block)->len > 0) { ADD_BLOCK(); } if ( NIL_P(refs) && rb_funcall(refs_found, rb_intern("empty?"), 0) == Qfalse ) { return superredcloth_transform(rb_formatter, orig_p, orig_pe, refs_found); } else { rb_funcall(rb_formatter, rb_intern("after_transform"), 1, html); return html; } }
47. %%{ machine superredcloth_scan; include superredcloth_common "ext/superredcloth_scan/superredcloth_common.rl"; action extend { extend = rb_hash_aref(regs, ID2SYM(rb_intern("type"))); } # blocks notextile_tag_start = "<notextile>" ; notextile_tag_end = "</notextile>" CRLF? ; notextile_block_start = ( "notextile" >A %{ STORE(type) } A C :> "." ( "." %extend | "" ) " "+ ) ; pre_tag_start = "<pre" [^>]* ">" (space* "<code>")? ; pre_tag_end = ("</code>" space*)? "</pre>" CRLF? ; pre_block_start = ( "pre" >A %{ STORE(type) } A C :> "." ( "." %extend | "" ) " "+ ) ; bc_start = ( "bc" >A %{ STORE(type) } A C :> "." ( "." %extend | "" ) " "+ ) ; btype = ( "p" | "h1"... block_start = ( btype >A %{ STORE(type) } A C :> "." ( "." %extend | "" ) " "+ ) ; next_block_start = ( btype A C :> "."+ " " ) >A @{ p = reg - 1; } ; pre_tag := |* pre_tag_end { CAT(block); DONE(block); fgoto main; }; default => esc_pre; *|; notextile_tag := |* notextile_tag_end { DONE(block); fgoto main; }; default => cat; *|; }%%
48. %%{ machine superredcloth_scan; include superredcloth_common "ext/superredcloth_scan/superredcloth_common.rl"; action extend { extend = rb_hash_aref(regs, ID2SYM(rb_intern("type"))); } # blocks notextile_tag_start = "<notextile>" ; notextile_tag_end = "</notextile>" CRLF? ; notextile_block_start = ( "notextile" >A %{ STORE(type) } A C :> "." ( "." %extend | "" ) " "+ ) ; pre_tag_start = "<pre" [^>]* ">" (space* "<code>")? ; pre_tag_end = ("</code>" space*)? "</pre>" CRLF? ; pre_block_start = ( "pre" >A %{ STORE(type) } A C :> "." ( "." %extend | "" ) " "+ ) ; bc_start = ( "bc" >A %{ STORE(type) } A C :> "." ( "." %extend | "" ) " "+ ) ; btype = ( "p" | "h1"... block_start = ( btype >A %{ STORE(type) } A C :> "." ( "." %extend | "" ) " "+ ) ; next_block_start = ( btype A C :> "."+ " " ) >A @{ p = reg - 1; } ; pre_tag := |* pre_tag_end { CAT(block); DONE(block); fgoto main; }; default => esc_pre; *|; notextile_tag := |* notextile_tag_end { DONE(block); fgoto main; }; default => cat; *|; }%%
49. %%{ machine superredcloth_scan; include superredcloth_common "ext/superredcloth_scan/superredcloth_common.rl"; action extend { extend = rb_hash_aref(regs, ID2SYM(rb_intern("type"))); } # blocks notextile_tag_start = "<notextile>" ; notextile_tag_end = "</notextile>" CRLF? ; notextile_block_start = ( "notextile" >A %{ STORE(type) } A C :> "." ( "." %extend | "" ) " "+ ) ; pre_tag_start = "<pre" [^>]* ">" (space* "<code>")? ; pre_tag_end = ("</code>" space*)? "</pre>" CRLF? ; pre_block_start = ( "pre" >A %{ STORE(type) } A C :> "." ( "." %extend | "" ) " "+ ) ; bc_start = ( "bc" >A %{ STORE(type) } A C :> "." ( "." %extend | "" ) " "+ ) ; btype = ( "p" | "h1"... block_start = ( btype >A %{ STORE(type) } A C :> "." ( "." %extend | "" ) " "+ ) ; next_block_start = ( btype A C :> "."+ " " ) >A @{ p = reg - 1; } ; pre_tag := |* pre_tag_end { CAT(block); DONE(block); fgoto main; }; default => esc_pre; *|; notextile_tag := |* notextile_tag_end { DONE(block); fgoto main; }; default => cat; *|; }%% /* * redcloth_scan.c.rl * * Copyright (C) 2009 Jason Garber */ #define redcloth_scan_c #define RSTRING_NOT_MODIFIED #include <ruby.h> #include "redcloth.h" VALUE mRedCloth, super_ParseError, super_RedCloth, super_HTML, super_LATEX; VALUE SYM_escape_preformatted, SYM_escape_attributes; #line 23 "ext/redcloth_scan/redcloth_scan.c" static const unsigned char _redcloth_scan_actions[] = { 0, 1, 0, 1, 2, 1, 3, 1, 4, 1, 5, 1, 6, 1, 7, 1, 9, 1, 10, 1, 11, 1, 12, 1, 13, 1, 14, 1, 15, 1, 16, 1, 17, 1, 18, 1, 19, 1, 20, 1, 21, 1, 22, 1, 23, 1, 24, 1, 25, 1, 26, 1, 27, 1, 28, 1, 29, 1, 30, 1, 34, 1, 35, 1, 36, 1, 38, 1, 40, 1, 42, 1, 43, 1, 44, 1, 45, 1, 48, 1, 57, 1, 58, 1, 59, 1, 60, 1, 61, 1, 62, 1, 63, 1, 64, 1, 65, 1, 66, 1, 70, 1, 73, 1,
53. grammar Arithmetic rule additive multitive ( '+' multitive )* end rule multitive primary ( [*/%] primary )* end rule primary '(' additive ')' / number end rule number '-'? [1-9] [0-9]* end end
54. require 'parslet' class MiniParser < Parslet::Parser rule(:integer) { match('[0-9]').repeat(1) } root(:integer) end MiniParser.new.parse("1324321") # => "1324321"@0
55. Parslet::Atoms str('Boston')
56. Parslet::Atoms str('Boston').parse('Boston')
57. Parslet::Atoms str('Boston').parse('Boston') # => "Boston"@0
58. Parslet::Atoms str('Boston').parse('Boston') # => "Boston"@0 match('[0-9a-f]')
59. Parslet::Atoms str('Boston').parse('Boston') # => "Boston"@0 match('[0-9a-f]') any
60. Operators str('Wicked') >> str('Good') str('Ruby') | str('Elixir') match('[Bb]') >> str('oston') | match('[Mm]') >> str('assachusetts')
61. Repetition str('foo').repeat str('foo').repeat(1) str('foo').repeat(1,3) str('foo').repeat(0, nil) str('foo').maybe
62. Presence str('Java') >> str('Script').present? str('0').repeat(1).absent? >> match('[\d]').repeat(1)
63. 1. Create a grammar What should be legal syntax? 2. Annotate the grammar: What is important data? 3. Create a transformation: How do I want to work with that data?
64. 1. Create a grammar What should be legal syntax? 2. Annotate the grammar: What is important data? 3. Create a transformation: How do I want to work with that data?
65. Capture str('Common').parse('Common') # => "Common"@0 str('Common').as(:park).parse('Common') # => {:park=>"Common"@0}
66. Capture str('a').repeat.as(:b) # => {:b=>"aaa"@0} str('a').as(:b).repeat # => [{:b=>"a"@0}, {:b=>"a"@1}, {:b=>"a"@2}] str('a').as(:a) >> str('b').as(:b) >> str('c') # => {:a=>"a"@0, :b=>"b"@1}
67. rule(:table) do (str("table") >> attributes?.as(:attributes) >> str(".\n")).maybe >> table_row.repeat(1).as(:content) >> block_end end rule(:table_row) do table_row_attributes >> table_row_content >> end_table_row end rule(:table_row_attributes) { (attributes?.as(:attributes) >> str(". ")).maybe } rule(:table_row_content) { (table_header | table_data).repeat(1).as(:content) } rule(:end_table_row) { str("|") >> (block_end.present? | (str("\n"))) } rule(:table_header) do str("|_. ") >> table_content.as(:content) end rule(:table_data) do str("|") >> str("\n").absent? >> td_attributes? >> table_content.as(:content) end
68. table(#prices). | Adults | $5 | | Children | $2 | <table id="prices"> <tr> <td>Adults</td> <td>$5</td> </tr> <tr> <td>Children</td> <td>$2</td> </tr> </table>
69. rule(:table) do (str("table") >> attributes?.as(:attributes) >> str(".\n")).maybe >> table_row.repeat(1).as(:content) >> block_end end rule(:table_row) do table_row_attributes >> table_row_content >> end_table_row end rule(:table_row_attributes) { (attributes?.as(:attributes) >> str(". ")).maybe } rule(:table_row_content) { (table_header | table_data).repeat(1).as(:content) } rule(:end_table_row) { str("|") >> (block_end.present? | (str("\n"))) } rule(:table_header) do str("|_. ") >> table_content.as(:content) end rule(:table_data) do str("|") >> str("\n").absent? >> td_attributes? >> table_content.as(:content) end
70. def parenthesized(atom) str('(') >> atom >> str(')') end parenthesized(match['\d']).parse("(500)")
71. class HtmlTag < Parslet::Parser root(:tag) rule(:tag) { open_tag | close_tag | self_closing_tag | comment_tag } rule(:open_tag) { str("<") >> tag_name >> attributes? >> str(">") } rule(:close_tag) { str("</") >> tag_name >> str(">") } rule(:tag_name) { match("[A-Za-z_:]") >> name_char.repeat } ... end class BlockHtmlTag < HtmlTag rule(:tag_name) do inline_tag_name.absent? >> any_tag_name end rule(:inline_tag_name) do INLINE_TAGS.map {|name| str(name) }.reduce(:|) end end
72. > HtmlTag.new.open_tag.methods => [:name, :block, :try, :parslet, :to_s_inner, :parse, :apply, :cached?, ...] > HtmlTag.new.open_tag.parse("<blockquote>") => "<blockquote>"@0 > HtmlTag.new.open_tag.parse("</blockquote>") Parslet::ParseFailed: Failed to match sequence ('<' TAG_NAME ATTRIBUTES? '>') at line 1 char 2. from /Users/jasongarber/.rvm/gems/ruby-2.0.0-p247/gems/parslet-1.5.0/lib/parslet/ cause.rb:63:in `raise' from /Users/jasongarber/.rvm/gems/ruby-2.0.0-p247/gems/parslet-1.5.0/lib/parslet/ atoms/base.rb:46:in `parse' from (irb):8 from /Users/jasongarber/.rvm/rubies/ruby-2.0.0-p247/bin/irb:16:in `<main>'
73. begin RedClothParslet::Parser::BlockHtmlTag.new.tag.parse("<img>") rescue Parslet::ParseFailed => failure puts failure.cause.ascii_tree end Expected one of [OPEN_TAG, CLOSE_TAG, SELF_CLOSING_TAG, COMMENT_TAG] at line 1 char 1. |- Failed to match sequence ('<' TAG_NAME ATTRIBUTES? '>') at line 1 char 2. | `- Failed to match sequence ((!INLINE_TAG_NAME / &(INLINE_TAG_NAME NAME_CHAR{1, })) ANY_TAG_NAME) at line 1 char 2. | `- Expected one of [!INLINE_TAG_NAME, &(INLINE_TAG_NAME NAME_CHAR{1, })] at line 1 char 2. | |- Input should not start with INLINE_TAG_NAME at line 1 char 2. | `- Input should start with INLINE_TAG_NAME NAME_CHAR{1, } at line 1 char 2. |- Failed to match sequence ('</' TAG_NAME '>') at line 1 char 1. | `- Expected "</", but got "<i" at line 1 char 1. |- Failed to match sequence ('<' TAG_NAME ATTRIBUTES? SPACES? '/' '>') at line 1 char 2. | `- Failed to match sequence ((!INLINE_TAG_NAME / &(INLINE_TAG_NAME NAME_CHAR{1, })) ANY_TAG_NAME) at line 1 char 2. | `- Expected one of [!INLINE_TAG_NAME, &(INLINE_TAG_NAME NAME_CHAR{1, })] at line 1 char 2. | |- Input should not start with INLINE_TAG_NAME at line 1 char 2. | `- Input should start with INLINE_TAG_NAME NAME_CHAR{1, } at line 1 char 2. `- Failed to match sequence ('<!--' (!COMMENT_TAG_END .){0, } COMMENT_TAG_END) at line 1 char 1. `- Expected "<!--", but got "<img" at line 1 char 1.
74. I Objects
75. describe RedClothParslet::Parser::HtmlTag do it { should parse("<div>") } it { should parse("<hr />") } it { should parse("</div>") } it { should parse("<!-- an HTML comment -->") } describe "attribute" do subject { described_class.new.attribute } it { should parse(" class='awesome'") } it { should_not parse(' 9kittens="cute"') } end end
76. $ rspec spec/parser/html_tag_spec.rb 1) RedClothParslet::Parser::HtmlTag tag Failure/Error: it { should parse("</div>") } expected TAG to be able to parse "</div>" Expected one of [OPEN_TAG, CLOSE_TAG, SELF_CLOSING_TAG, COMMENT_TAG] at line 1 char 1. |- Failed to match sequence ('<' TAG_NAME ATTRIBUTES? '>') at line 1 char 2. | `- Failed to match sequence ([A-Za-z_:] NAME_CHAR{0, }) at line 1 char 2. | `- Failed to match [A-Za-z_:] at line 1 char 2. |- Failed to match sequence ('<' TAG_NAME '>') at line 1 char 2. | `- Failed to match sequence ([A-Za-z_:] NAME_CHAR{0, }) at line 1 char 2. | `- Failed to match [A-Za-z_:] at line 1 char 2. |- Failed to match sequence ('<' TAG_NAME ATTRIBUTES? SPACES? '/' '>') at line 1 char 2. | `- Failed to match sequence ([A-Za-z_:] NAME_CHAR{0, }) at line 1 char 2. | `- Failed to match [A-Za-z_:] at line 1 char 2. `- Failed to match sequence ('<!--' (!COMMENT_TAG_END .){0, } COMMENT_TAG_END) at line 1 char 1. `- Expected "<!--", but got "</di" at line 1 char 1. # ./spec/parser/html_tag_spec.rb:9:in `block (3 levels) in <top (required)>' 13/13: 100% |==========================================| Time: 00:00:00 Finished in 0.01879 seconds 13 examples, 1 failure
77. 1. Create a grammar What should be legal syntax? 2. Annotate the grammar: What is important data? 3. Create a transformation: How do I want to work with that data?
78. Transformations tree = {left: {int: '1'}, op: '+', right: {int: '2'}} class T < Parslet::Transform rule(int: simple(:x)) { Integer(x) } end T.new.apply(tree) # => {:left=>1, :op=>"+", :right=>2}
79. Transformations tree = {left: {int: '1'}, op: '+', right: {int: '2'}} class T < Parslet::Transform rule(int: simple(:x)) { Integer(x) } rule(op: '+', left: simple(:l), right: simple(:r)) { l + r } end T.new.apply(tree) # => 3
80. Transformations rule(:content => subtree(:c), :attributes => subtree(:a)) do |dict| {:content => dict[:c], :opts => RedCloth::Ast::Attributes.new(dict[:a])} end rule(:table => subtree(:a)) do RedCloth::Ast::Table.new(a[:content], a[:opts]) end rule(:bq => subtree(:a)) do RedCloth::Ast::Blockquote.new(a[:content], a[:opts]) end
81. Who you callin’ slow?
82. class ErbParser < Parslet::Parser rule(:ruby) { (str('%>').absent? >> any).repeat.as(:ruby) } rule(:expression) { (str('=') >> ruby).as(:expression) } rule(:comment) { (str('#') >> ruby).as(:comment) } rule(:code) { ruby.as(:code) } rule(:erb) { expression | comment | code } rule(:erb_with_tags) { str('<%') >> erb >> str('%>') } rule(:text) { (str('<%').absent? >> any).repeat(1) } rule(:text_with_ruby) { (text.as(:text) | erb_with_tags).repeat.as(:t root(:text_with_ruby) end
83. class ErbParser < Parslet::Parser rule(:ruby) { (str('%>').absent? >> any).repeat.as(:ruby) } rule(:expression) { (str('=') >> ruby).as(:expression) } rule(:comment) { (str('#') >> ruby).as(:comment) } rule(:code) { ruby.as(:code) } rule(:erb) { expression | comment | code } rule(:erb_with_tags) { str('<%') >> erb >> str('%>') } rule(:text) { (str('<%').absent? >> any).repeat(1) } rule(:text_with_ruby) { (text.as(:text) | erb_with_tags).repeat.as(:t root(:text_with_ruby) end class ErbParser < Parslet::Parser rule(:ruby) { (str('%>').absent? >> any).repeat.as(:ruby) } rule(:expression) { (str('=') >> ruby).as(:expression) } rule(:comment) { (str('#') >> ruby).as(:comment) } rule(:code) { ruby.as(:code) } rule(:erb) { expression | comment | code } rule(:erb_with_tags) { str('<%') >> erb >> str('%>') } rule(:text) { (str('<%').absent? >> any).repeat(1) } rule(:text_with_ruby) { (text.as(:text) | erb_with_tags).repeat.as(:t root(:text_with_ruby) end
84. class ErbParser < Parslet::Parser rule(:ruby) { (str('%>').absent? >> any).repeat.as(:ruby) } rule(:expression) { (str('=') >> ruby).as(:expression) } rule(:comment) { (str('#') >> ruby).as(:comment) } rule(:code) { ruby.as(:code) } rule(:erb) { expression | comment | code } rule(:erb_with_tags) { str('<%') >> erb >> str('%>') } rule(:text) { (str('<%').absent? >> any).repeat(1) } rule(:text_with_ruby) { (text.as(:text) | erb_with_tags).repeat.as(:t root(:text_with_ruby) end class ErbParser < Parslet::Parser rule(:ruby) { (str('%>').absent? >> any).repeat.as(:ruby) } rule(:expression) { (str('=') >> ruby).as(:expression) } rule(:comment) { (str('#') >> ruby).as(:comment) } rule(:code) { ruby.as(:code) } rule(:erb) { expression | comment | code } rule(:erb_with_tags) { str('<%') >> erb >> str('%>') } rule(:text) { (str('<%').absent? >> any).repeat(1) } rule(:text_with_ruby) { (text.as(:text) | erb_with_tags).repeat.as(:t root(:text_with_ruby) end include Parslet::Accelerator optimized = apply( parser, rule( (str(:x).absent? >> any).repeat ) { GobbleUp.new(x, 0) } )
85. Custom Atoms • Parse a limited set of natural-language queries • “Who makes the best cheesesteaks in Boston?” • EngTagger: a corpus-trained, probabilistic tagger • Custom Parslet::Atom
86. rule(:question) do interrogative.maybe.as(:int) >> verb_phrase.maybe.as(:verb) >> superlative_phrase.maybe.as(:sup) >> subject.as(:subj) >> prepositional_phrase.repeat.as(:preps) >> sentence_end.repeat.as(:punct) end rule(:verb_phrase) { (verb_present | verb_past | verb_future).as(:vp) } rule(:verb_present) { word(:VBZ, :VB).as(:present) } rule(:verb_past) { word(:VBD).as(:past) } rule(:verb_future) { word(:MD).as(:future) >> word(:VB).maybe.as(:infinitive) }
87. Other Crazy Uses
88. Other Crazy Uses •User-supplied formulas / logic
89. Other Crazy Uses •User-supplied formulas / logic •Logs
90. Other Crazy Uses •User-supplied formulas / logic •Logs •Streaming text
91. Other Crazy Uses •User-supplied formulas / logic •Logs •Streaming text •The Right Reverend and Right Honourable the Lord Bishop of London Richard John Carew Chartres
92. Who will write the next awesome DSL?
93. Who will write the next awesome DSL!. You
94. Conclusions
95. Conclusions • DSLs make life better
96. Conclusions • DSLs make life better • internal_dsl > external_dsl if internal_dsl.practicable?
97. Conclusions • DSLs make life better • internal_dsl > external_dsl if internal_dsl.practicable? • Keep your parser clean
98. Conclusions • DSLs make life better • internal_dsl > external_dsl if internal_dsl.practicable? • Keep your parser clean • “Situational awareness!”
99. @jasongarber @promptworks jason@promptworks.com