2015-FSE-Suggesting accurate method and class names

SuggestingAccurateMethodandClassNames

MiltiadisAllamanis

School

EarlT.Barr

Dept.

ChristianBird CharlesSutton

ResearchMicrosoft

Redmond,WA,USA

Microsoft

{m.allamanis,csutton}@ed.ac.ukofInformatics

UniversityofEdinburghEdinburgh,EH89AB,UKofComputerScienceUniversityCollegeLondon

London,UK

e.barr@ucl.ac.ukcbird@http://www.77cn.com.cn

ABSTRACT

Descriptivenamesareavitalpartofreadable,andhencemaintain-able,code.Recentprogressonautomaticallysuggestingnamesforlocalvariablestantalizeswiththeprospectofreplicatingthatsuccesswithmethodandclassnames.However,suggestingnamesformeth-odsandclassesismuchmoredif cult.Thisisbecausegoodmethodandclassnamesneedtobefunctionallydescriptive,butsuggestingsuchnamesrequiresthatthemodelgoesbeyondlocalcontext.Weintroduceaneuralprobabilisticlanguagemodelforsourcecodethatisspeci callydesignedforthemethodnamingproblem.Ourmodellearnswhichnamesaresemanticallysimilarbyassigningthemtolocations,calledembeddings,inahigh-dimensionalcontin-uousspace,insuchawaythatnameswithsimilarembeddingstendtobeusedinsimilarcontexts.Theseembeddingsseemtocontainsemanticinformationabouttokens,eventhoughtheyarelearnedonlyfromstatisticalco-occurrencesoftokens.Furthermore,weintroduceavariantofourmodelthatis,toourknowledge,the rstthatcanproposeneologisms,namesthathavenotappearedinthetrainingcorpus.Weobtainstateoftheartresultsonthemethod,class,andeventhesimplervariablenamingtasks.Morebroadly,thecontinuousembeddingsthatarelearnedbyourmodelhavethepotentialforwideapplicationwithinsoftwareengineering.CategoriesandSubjectDescriptors:

D.2.3[SoftwareEngineering]:CodingToolsandTechniquesGeneralTerms:Algorithms

Keywords:Codingconventions,naturalnessofsoftware“Youshallknowawordbythecompanyitkeeps.”

—J.R.Firth

1.INTRODUCTION

Languagestartswithnames.Whileprogramming,developersmustnamevariables,parameters,functions,classes,and les.Theystrivetochoosenamesthataremeaningfulandconventional,i.e.consistentwithothernamesusedinrelatedcontextsintheircodebase.Indeed,leadingindustrialexperts,includingBeck[9],Mc-Connell[34],andMartin[33],havestressedtheimportanceofidenti ernaminginsoftware.Findinggoodnamesforprogram-minglanguageconstructsisdif cult;poornamesmakecodehardertounderstandandmaintain[29,50,30,7].Empiricalevidence

Permissiontomakedigitalorhardcopiesofallorpartofthisworkforpersonalorclassroomuseisgrantedwithoutfeeprovidedthatcopiesarenotmadeordistributedforpro torcommercialadvantageandthatcopiesbearthisnoticeandthefullcitationonthe rstpage.Tocopyotherwise,torepublish,topostonserversortoredistributetolists,requirespriorspeci cpermissionand/orafee.

FSE’15,August30–September4,2015,Bergamo,ItalyCopyright2015ACMX-XXXXX-XX-X/XX/XX...$15.00.

suggeststhatpoornamesalsoleadtosoftwaredefects[13,1].Codemaintenanceexacerbatesthedif cultyof ndinggoodnames,be-causetheappropriatenessofanamechangesovertime:anexcellentchoice,atthetimeaconstructisintroduced,candegradeintoapoorname,aswhenavariableisusedinnewcontextorafunction’ssemanticschanges.

Namesofmethodsandclassesareparticularlyimportant,andcanbedif culttochoose.Høstetal.eloquentlycapturedtheirimportance:“Methodsarethesmallestnamedunitsofaggregatedbehaviorinmostconventionalprogramminglanguagesandhencethecornerstoneofabstraction”[26].Semanticallydistinctmethodnamesarethebasictoolsforreasoningaboutprogrambehaviour.Programmersdirectlythinkintermsofthesenamesandtheircom-positions,sinceaprogrammerchosethemfortheunitsintowhichtheprogrammerdecomposedaproblem.Moreover,methodnamescanbehardtochange,especiallywhentheyareusedinanAPI.Whenpublishedinapopularlibrary,methodnamingdecisionsareespeciallyrigidandpoornamescandoomaprojecttoirrelevance.Inthispaper,wesuggestthatmodernstatisticaltoolsallowustoautomaticallysuggestdescriptive,idiomaticmethodandclassnamestoprogrammers.Wetacklethemethodnamingproblem:theproblemofinferringamethod’snamefromitsbody(oraclassfromitsmethods).Asdevelopersspendapproximatelyhalfoftheirdevelopmenttimetryingtounderstandandcomprehendcodeduringmaintenancealone[17],anyprogresstowardsolvingthemethodnamingproblemwillimprovethecomprehensibilityofcode[49]leadingtoanincreaseprogrammerproductivity[24].

Inpreviouswork,weintroducedtheNATURALIZEframework[2],whichlearnsthecodingconventionsusedinacodebaseandtacklesonenamingproblemprogrammersface—thatofnamingvariables—byexploitingthe“naturalness”orpredictabilityofcode[25].However,themethodnamingproblemismuchmoredif cultthanthevariablenamingproblem,becausetheappropriatenessofmethodandclassnamesdependsnotsolelyontheirusesbutalsoontheirinternalstructure—theirbodyortheirsetofmethods.Anadequatenamemustdescribenotjustwhatthemethodis,butwhatitdoes.Variablenames,bycontrast,canoftenbepredictedsolelyfromafewtokensoflocalcontext;forexample,itiseasytopredictthevariablenamethatfollowsthetokensfor(int.Becausemethodandclassnamesmustbefunctionallydescriptive,theyoftenhaverichinternalstructure:methodnamesareoftenverbphrasesandclassnamesareoftennounphrases.Butthismeansthatmethodandclassnamesareoftenneologisms,thatis,namesnotseeninthetrainingcorpus.Existingprobabilisticmodelsofsourcecode,includingthen-grammodelsusedinNATURALIZE,cannotsuggestneologisms.Theseaspectsofthemethodnamingproblemseverelyexacerbatethedatasparsityproblemfacedbyallprobabilisticlanguagemodels,becauseaddressingthembybuildingmodelsthatconsidermorecontextnecessarilymeansthatanyindividualcontextwillbeobservedlessoften.Therefore,themethodnamingproblemrequiresmodelsthat

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