Understanding mobile-specific code smells Presented by: Sarra - PowerPoint PPT Presentation

Understanding mobile-specific code smells Presented by: Sarra Habchi Advisor: Examiners: - Romain Rouvoy - Jean-Christophe Routier Rapporteurs: - Naouel Moha - Andy Zaidman - Tegawendé-François Bissyande - Yann-Gaël Guéhéneuc

2 Raconteur.net

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Performance matters! 9

Performance practices matter! 10

Performance bad practices 11

Performance bad practices ● Resource leaks (Guo et al. 2013) ● 3 anti-patterns (Liu et al. 2014) ● 30 code smells (Reimann et al. 2014) → Mobile-specific code smells 12

Mobile-specific code smells ● Catalog ● Reused & extended in later studies ● 14 studies 13

Official documentation Catalog of 30 Developer Android code smells Semi-automated blogs & talks ... analysis performance Q&A forums 14

UI Overdraw 15

1 overdraw 2 overdraws 3 overdraws 4 overdraws 16

Detection tools 17

Detection tools ● Paprika (Hecht et al. 2015) ● aDoctor (Palomba et al. 2017) ● MOGP approach (Kessentini and Ouni 2017) 18

Impact on performance 19

Impact on performance ● UI & Memory (Hecht et al. 2016) ● Energy (Carette et al. 2017) ● Energy (Palomba et al. 2019) 20

Code smell Detection Impact on catalog tools performance ? 21

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Causes Relevance Adequate tools 23

We have: Code smell Detection Impact on catalog tools performance We lack: Understand Refactoring Refactoring code smells catalog tools 24

1. Extent 2. Causes 3. Developers’ perception Understanding mobile code smells 25

1. Extent 2. Causes 3. Developers’ perception Understanding mobile code smells 26

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Code Smells in iOS Apps: How do they compare to Android? ● Identified 6 iOS-specific code smells ● Common code smells between Android and iOS ● Proposed a detection tool for iOS ● Android apps tend to have more smells than the iOS ones 28

1. Extent 2. Causes 3. Developers’ perception Understanding mobile code smells 29

1. Extent 2. Causes 3. Developers’ perception Understanding mobile code smells 30

Motives of technical debt (Tom et al. 2013) Pragmatism Prioritisation Process Attitudes Ignorance Oversight 31

Motives of technical debt (Tom et al. 2013) Pragmatism Prioritisation Process Attitudes Ignorance Oversight 32

Motives of technical debt (Tom et al. 2013) Pragmatism Prioritisation Process Attitudes Ignorance Oversight 33

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1- Commits 2- Developers 3- Survival 35

1- Commits 2- Developers 3- Survival 36

Code smell Code smell removal introduction ... ... Commit 0 Commit 1 Commit k Commit n Instance A Instance A Instance A Instance A Instance B Instance B 37

Instance A Instance A Instance C ... Commit p Commit m ... ... Commit 0 Commit 1 Commit k Commit n Instance A Instance A Instance A Instance A Instance B Instance B 38

RegistrationSocket.java GcmSocket.java Commit 303d1ac : File renaming link Instance Instance RegistrationSocket$Verification GcmSocket$Verification 39

Branches + Renamings 40

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Sniffer Git link to 1 -Extract app 2 - Detect 3 - Analyse Instances Commits an app data code smells change history Full code Repository smell history model 42

Sniffer ● Track branches ● Detect renamings ● Validated with: ○ F1-score=0.96 43

Dataset ● 324 open-source apps ● 255,000 commits ● 4,525 developers 44

LIC Leaking Inner Class MIM Member Ignoring Method NLMR No Low Memory Resolver HMU HashMap Usage UIO UI Overdraw UHA Unsupported Hardware Acceleration IOD Init OnDraw UCS Unsuited Cache Size 45

Introductions 46

% Removals 47

79% of code smell instances are removed 48

Intended removal? 49

No Low Memory Resolver 50

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Source code deletion 53

% Removals by deletion 54

59% of code smell removals are accompanied with source code deletion 55

Manual analysis ● 561 code smell instances ○ Commit actions ○ Commit message 56

How are code smells removed? ● Removal is a side effect of evolution ○ Source code deleted ○ Empty methods filled (MIM) 57

How are code smells removed? ● Only refactoring: ○ Code smells detected by Android Lint ■ Init OnDraw (IOD) ■ UI Overdraw (UIO) 58

Most of code smell removals are a side-effect of other activities 59

Motives of technical debt Pragmatism Prioritisation Process Attitudes Ignorance Oversight 60

How do releases impact code smell introductions and removals? 61

1 Day 1 Week 1 Month 62

Releases do not have any impact on code smell introductions or removals. 63

Motives of technical debt Pragmatism Prioritisation Process Attitudes Ignorance Oversight 64

1- Commits 2- Developers 3- Survival 65

1- Commits 2- Developers 3- Survival 66

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Who is involved? 68

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Mainly 38% 1 commit 70

Involved developers 71

Introducers Removers 72

Introducers 18% 73

Introducers BOTH Removers 18% 8% 74

Expected Removals Introductions 75

⍴ = 0.77 76

Introducers ≃ Removers 77

Seniority and code smells ● Contribution = commits/project size ● Reputation ≃ followers “Developers with lots of followers were treated as local celebrities. Their activities were retold almost as local parable” 78 (Dabbish et al. 2012)

⍴ = 0.27 ⍴ = 0.24 79

Junior Senior Junior Senior → Seniority does not impact developers’ behavior 80

● Introducers ⋍ Removers ● Newcomer ⟹ Bad contributor ฀ ● Senior || Reputable ⟹ Good contributor ฀ 81

Motives of technical debt Pragmatism Prioritisation Process Attitudes Ignorance Oversight 82 82

1- Commits 2- Developers 3- Survival 83

1- Commits 2- Developers 3- Survival 84

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Survival analysis ● S(t) = Probability(t < T) ● T: a random lifetime from the population “Chances for a code smell to be still present in the source code after t time” ● 180.000 code smell lifelines 86

441 days 14 months 87

9 commits 88

14 months vs. 9 effective commits 89

Variables: project properties ● Project size ○ #Classes ○ #Commits ○ #Developers ● Project releases ○ #Releases ○ Cycle 90

Variables: Code smell properties ● Tool integration ○ Linted (detectable by Android Lint) ○ Linter priority ● Code smell type ○ Granularity 91

Variables: Code smell properties ● Tool integration ○ Linted (detectable by Android Lint) ○ Linter priority ● Code smell type ○ Granularity 92

→ Static analysers have an impact on mobile code smells → Tool prioritisation matters 93

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Motives of technical debt Pragmatism Prioritisation Process Attitudes Ignorance Oversight 95 95

1. Extent 2. Causes: - Change history 3. Developers’ perception Understanding mobile code smells 96

1. Extent 2. Causes: - Change history 3. Developers’ perception Understanding mobile code smells 97

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Catalog of performance code smells How do they use the linter to deal with performance concerns? 99

Semi-structured Experienced Interviews Android developers Analytical strategy Qualitative approach of (Schmidt et al. 2004) 100 100