The Even Darker Art of Rails Engines

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The Even-Darker Art of Rails Engines

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@lazyatom

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github.com/lazyatom/engines

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Rails 2.3

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history

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November 2005

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it’s distracting!

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reuse is overrated!

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Evil! Evil! Evil! Evil! Evil! Evil! Evil! Evil! Shit!

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eek!

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appable_plugins

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desert

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merb slices?

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engines

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!"#$%&!"#$'#(%&$#)&!"#$%&*$+,#-.!) !"#$%&'() $$*%&'()$++,$-'%!.%&'()./0#'12%)/'0 "0! 3$405/0"6$%1"$7-(5/06$8/)9$%0$%77:$!/1";)'1<= !"#$"05/0"> $$9%6.%77.!/1";)'1<> "0! 3$?")(106$)1("$/#$)9"$"05/0"$69/76$8/)9$%$1'()/05$#/-" !"#$1'()"!> $$@/-"="A/6)>B1'()/05.#/-"C "0! !"#$D/"8.7%)9 $$@/-"=E'/0B!/1";)'1

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app/controllers/ models/ helpers/ views/ metal/

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*$+,#-&"**&23-'!3$$(!&*$+,#-523-'!3$$(!.!) ;-%66$H-(5/0I'0)1'--"1/0/1**$#2"'#3-43-'!3$$(! $$!"#$/0!"A $$$$1"0!"1$J)"A)$,K$LM"--'F$H-(5/0NL $$"0! "0!

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9"-7"1$J%-- won’t load from your plugin

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Ticket #1905

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conﬁg/routes.rb

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O;)/'0I'0)1'--"1JJ?'()/05JJ?'()"6=!1%8$!'$+2%7+ $$2%7=;'00";)$G:7%)9GF$J;'0)1'--"1$,K$L7-(5/0LF$ $$$$$$$$$$$$$$$$$$$$$$$J%;)/'0$,K$L/0!"AL "0! *$+,#-&23-6#,&!3+'(%.!)

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top precedence

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O;)/'0I'0)1'--"1JJ?'()/05JJ?'()"6=!1%8$!'$+2%7+ $$2%7=;'00";)$G:7%)9GF$J;'0)1'--"1$,K$L7-(5/0LF$ $$$$$$$$$$$$$$$$$$$$$$$J%;)/'0$,K$L/0!"AL "0! O;)/'0I'0)1'--"1JJ?'()/05JJ?'()"6=!1%8$!'$+2%7+ $$3$===$')9"1$1'()"6$=== $$2%7=;'00";)$G:7%)9GF$J;'0)1'--"1$,K$L%77LF$ $$$$$$$$$$$$$$$$$$$$$$$J%;)/'0$,K$L/0!"AL $$3$===$')9"1$1'()"6$=== "0! in your plugin: in your app:

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Ticket #2592 (also Ticket #329)

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785*$+,#-&$#)&785*$+,#-.!) 2'!(-"$P

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what’s missing?

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public assets

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copy

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ﬁle clash

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83+!5*$+,#--%'"$$.!) 2<./2%5"6$,$H%)90%2"=0"8B@/-"=!/10%2"B..@QR4..CC$S$ $$$$$$$$$$$$$$L%66")6:/2%5"6L )%15")$,$?%/-6=1'')$S$L7(&-/;:/2%5"6:2<.7-(5/0L @/-"T)/-6=2U!/1.7B)%15")C 2<./2%5"6=;9/-!1"0="%;9$!'$+"+$ $$$$@/-"T)/-6=;7.1B"F$)%15")$S$"=&%6"0%2"C$ "0!

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83+!5*$+,#--%'"$$.!) 2<./2%5"6$,$H%)90%2"=0"8B@/-"=!/10%2"B..@QR4..CC$S$ $$$$$$$$$$$$$$L%66")6:/2%5"6L )%15")$,$?%/-6=1'')$S$L7(&-/;:/2%5"6:2<.7-(5/0L )%15")=2%U".6<2-/0UB2<./2%5"6C$(0-"66$)%15")="A/6)>

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migrations

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simple DSL

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rollback

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!&:2/51%)": $$VWWXWYWYYVYVZ[.%-79%=1& version 20090101121234 20090102142345 2008123123456 VWWXWYWVY[VZ[\.&")%=1& 7-(5/0:!&:2/51%)": $$VWW]YVZYZ[\^.5%22%=1&

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version 20090101121234 20090102142345 2008123123456 1%U"$!&J1'--&%;U P/51%)'1=1'--&%;U P/51%)'13;(11"0).D"16/'0 P/51%)'132/51%)"!=-%6) P/51%)'1=5").%--.D"16/'06 BL_4R4I`$D"16/'0$@?aP$ $ $ $$6;9"2%.2/51%)/'06LC =2%7BbJ)'./C=6'1)

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it gets worse

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!&:2/51%)": $$WWY.%-79%=1& version 001 002 WWV.&")%=1& 7-(5/0:!&:2/51%)": $$WWY.5%22%=1&

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http://www.ﬂickr.com/photos/bk2204/475332962/

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single timeline

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app migration 1 app migration 2 plugin migration 1 app migration 3 plugin migra install upgrade You Me

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app migration 1 app migration 2 plugin migration 1 app migration 3 plugin migration 2 You

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WW[.!"-)%=1& !&:2/51%)": $$WWY.%-79%=1& WWV.&")%=1& 7-(5/0:!&:2/51%)": $$WWY.5%22%=1& WWZ.7-(5/0.)'.WWY=1&

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WW[.!"-)%=1& !&:2/51%)": $$WWY.%-79%=1& WWV.&")%=1& 7-(5/0:!&:2/51%)": $$WWY.5%22%=1& WWZ.7-(5/0.)'.WWY=1& Copy & Retimestamp? Reference? Symlink?

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Ticket #2058 interblah.net/plugin-migrations

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my recommendation? (for the moment, at least)

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write a generator c$6;1/7):5"0"1%)"$%;)6.%6.#(.2/51%)/'06 $$$$ $$$"A/6)6$$!&:2/51%)" $$$;1"%)"$$!&:2/51%)":VWWXW\W\YYYZZd.&-%9=1& c$=== (within your plugin)

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techniques

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overriding functionality

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views just work

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controllers

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straight override

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module

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namespaced

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playing nice with the class cache

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1/23*8/36/1**$#2"'#3-43-'!3$$(!/ 9"%/)((-/!(73:(;/6!37/'9(/73;+$(/ '!((/)+'/#%/%'#$$/"2'#:(<< < < < < < < !

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O;)/D"_(77'1)JJe"7"0!"0;/"6=-'%!.'0;".7%)96

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ApplicationController AppController PluginController

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ApplicationController PluginController

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23-6#,&(-:#!3-7(-'.!) ?%/-6JJQ0/)/%-/f"1=1(0$!'$+;'0#/5+ $$3$");=== $$;'0#/5=1"-'%!.7-(5/06$,$)1(" $$ "0!

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83+!5*$+,#-&"**&23-'!3$$(!%&,33;523-'!3$$(!.!) ;-%66$g''!I'0)1'--"1$h$=== $$(0-'%!%&-" $$ $$3$");$=== "0!

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init.rb woes

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;'0#/5=)'.71"7%1"$!' $$ "0! 785*$+,#--#'.!) $$_'2"O77I-%66="A)"0!BP

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testing

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ApplicationController PluginController AppController

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ApplicationController PluginController Their Code Your Code

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! " # $

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unit test?

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test in your own rails environment?

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plugin_test_helper

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I care about testing my chunk

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You care about testing your whole app

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empower the developer

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avoiding fail

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;%6"$;'!"=;'06(2"1 $$89"0$;'!"=%()9'1 $$$$1"(6"=2'6)-<$,j$:"##";)/D": $$89"0$1%0!B!"D"-'7"1C $$$$1"(6"=)1/;U/"1.&().7'66/&-"B)1("C $$"-6" $$$$1"(6"='D"11%)"!N "0!

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consume wisely

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Serving Size 14 kloc Nutrition Facts Amount Per Serving 1 bad engine Calories 10,666 Long Methods 1578g 34% God Objects 326g 7% Stress 320mg 119% Total Fat 2674g 98% Hairloss 45g 45.8% % Daily Value* Technical Debt 13g 87% Untested Code 1578mg 34% Hidden Bugs 326mg 7% Benefit 1mg 0.1%

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you will not be able to write some engines.

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you will not be able to use some engines.

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extract speciﬁc functionality

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establish some clear integration points

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you are customer #1

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READ the CODE

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james@lazyatom.com lets@gofreerange.com FIN