Do They Really Smell Bad? A Study on Developers' Perception of Bad Code Smells

Do They Really Smell Bad? A Study on Developers’ Perception of Bad Code SmellsFabio Palomba, Gabriele Bavota, Massimiliano Di Penta, Rocco Oliveto, Andrea De Lucia

ICSME 2014Victoria - CanadaOctober 1st, 2014

giovedì 2 ottobre 14

Context

Bad Code Smells


Bad Code Smells


Moha et al., “DECOR: A Method for the Specification and Detection of Code and Design Smells” - TSE 2010


van Emden et al., “Java Quality Assurance by Detecting Code Smells” - WCRE 2002


Tsantalis et al., “Identification of Move Method Refactoring Opportunities” - TSE 2009

Fokaets et al., “Identification and Application of Extract Class Refactorings In Object Oriented Systems” - JSS 2012

Tsantalis et al., “Identification of Extract Method Refactoring Opportunities for the Decomposition of Methods” - JSS 2011


Kessentini et al., “Deviance from Perfection is a Better Criterion than Closeness to Evil when Identifying Risky Code” - ASE 2010


Palomba et al., “Detecting Bad Smells in Source Code using Change History Information” - ASE 2013


Abebe et al., “Lexicon Bad Smells in Software” - WCRE 2009


Not only detection techniques! But also...


A. Chatzigeorgiou et al., “Investigating the evolution of bad smells in object-oriented code” - QUATIC 2010


R. Peters and A. Zaidman, “Evaluating the lifespan of code smells using software repository mining” - CSMR 2012

R. Arcoverde, A. Garcia, and E. Figueiredo, “Understanding the longevity of code smells: preliminary results of an explanatory survey” - IWRT 2011


F. Khomh, M. Di Penta, Y.-G. Guéhéneuc, and G. Antoniol, “An exploratory study of the impact of antipatterns on class change- and fault-proneness” - EMSE 2012

W. Li and R. Shatnawi, “An empirical study of the bad smells and class error probability in the post-release object-oriented system evolution” - JSS 2007


M. Abbes, F. Khomh,Y.-G. Guéhéneuc, and G. Antoniol, “An empirical study of the impact of two antipatterns, blob and spaghetti code, on program comprehension” - CSMR 2011


“We don’t see things as they are, we see things as we are” Anais Nin


S. M. Olbrich, D. S. Cruzes, and D. I. K. Sjøberg, “Are all code smells harmful? A study of God Classes and Brain Classes in the evolution of three open source systems” - ICSM 2010


A. Yamashita and L. Moonen, “Do developers care about code smells? An exploratory survey” - WCRE 2013


Investingating the developers’ point of view


RQ1: To what extent do bad smells reflect developers’ perception of design problems?



RQ1: To what extent do bad smells reflect developers’ perception of design problems?


RQ2: What are the bad smells that developers feel as the most harmful?


Study Design


Study DesignClass Data Should Be Private

Complex ClassFeature Envy

God ClassInappropriate Intimacy

Lazy ClassLong Method

Long Parameter ListMiddle Man

Refused BequestSpaghetti Code

Speculative Generality


Study DesignClass Data Should Be Private

Complex ClassFeature Envy

God ClassInappropriate Intimacy

Lazy ClassLong Method

Long Parameter ListMiddle Man

Refused BequestSpaghetti Code


Argo UML 0.34Eclipse 3.6.1

jEdit 4.5.1


Study Design

Original Developers: 10

Industrial Developers9

Master’s Students15

Argo UML 0.34Eclipse 3.6.1

jEdit 4.5.1

Class Data Should Be PrivateComplex Class

Feature EnvyGod Class

Inappropriate IntimacyLazy Class

Long MethodLong Parameter List

Middle ManRefused BequestSpaghetti Code



Study Design

Smelly Class

Developer


Study Design

Smelly Class

Developer

In your opinion, does this code component exhibit any design and/or implementation problem?


Study Design

Smelly Class

Developer


• If YES, please explain what are, in your opinion, the problems affecting the code component.


Study Design

Smelly Class

Developer


• If YES, please explain what are, in your opinion, the problems affecting the code component.

• If YES, please rate the severity of the design and/or implementation problem by assigning a score on the following five-points Likert scale: 1 (very low), 2 (low), 3 (medium), 4 (high), 5 (very high).


Resultsgiovedì 2 ottobre 14

Smells generally not Perceived as Design or Implementation Problems

Class Data Should Be Private

Middle Man

Lazy Class

Inappropriate Intimacy

Long Parameter List



Class Data Should Be Private

Middle Man

Lazy Class

Inappropriate Intimacy

< 25% perceived < 24% IDENTIFIED

< 10% perceived < 5% IDENTIFIED

< 36% PERCEIVED

< 20% PERCEIVED

< 30% PERCEIVED

< 20% IDENTIFIED

< 5% IDENTIFIED

< 13% IDENTIFIED

Long Parameter List



Class Data Should Be Private < 25% perceived < 24% IDENTIFIED

0

5

10

15

20

25

30

M I O

Identified Perceived




0

5

10

15

20

25

30

M I O


M I O

Severity

1 2 2




0

5

10

15

20

25

30

M I O


M I O

Severity

“This class exposes all its fields, and this could look like bad coding.

However, at the end of the day this is an utility class with public static

fields that can be used from everywhere in the system”


Smells generally Perceived and Identified by Respondents

Complex Class

God Class

Long Method

Spaghetti Code



Complex Class

God Class

Long Method

Spaghetti Code

> 85% perceived > 83% IDENTIFIED



> 68% perceived < 65% IDENTIFIED



God Class

0

17

33

50

67

83

100

M I O





God Class

0

17

33

50

67

83

100

M I O


M I O

Severity


4 5 5


Refused Bequest

Smells whose Perception may vary


Feature Envy


Refused Bequest



Feature Envy

DEPENDS FROM

THE “INTENSITY” OF

THE PROBLEM



Refused Bequest

0102030405060708090

100

ArgoUML Eclipse jEdit

Perceived Identified

Master Students Perception on the Three Analyzed Systems



Refused Bequest Master Students Perception on the Three Analyzed Systems

0102030405060708090

100

ArgoUML Eclipse jEdit

Perceived Identified

1

1

4


Conclusion


?giovedì 2 ottobre 14

Do They Really Smell Bad? A Study on Developers' Perception of Bad Code Smells

Software

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