ICSE’2016 | Austin | May 19, 2016

Davood Mazinanian Nikolaos Tsantalis

: Clone Refactoring

Raphael Stein Zackary Valenta

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38th International Conference on Software Engineering (ICSE'2016)Formal Tool Demonstration Session

Department of Computer Science and Software EngineeringConcordia University

ICSE’2016 | Austin | May 19, 2016

Clones are harmful

•Error-prone due to inconsistent updates(Juergens et al. @ ICSE’09)

• Increase maintenance effort and cost (Lozano et al. @ ICSM’08)

•Change-prone(Mondal et al. @ ACM SAC’12)

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ICSE’2016 | Austin | May 19, 2016

Clones are good

•Positive impact on maintainability(Kasper & Godfrey @ EMSE’08)

•Less buggyLess effort to fix bugs(Rahman, Bird & Devanbu @ EMSE’12)

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ICSE’2016 | Austin | May 19, 2016

Clone management

Clones that change frequently & are buggy might need some refactoring

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Motivation

Current clone refactoring support is poor

Tairas & Gray (IST’12) studied 1,200 Type-II clones detected in 9 open-source projects:• 10% could be refactored by Eclipse• CeDAR (IST’12) refactored 19%

We need better clone refactoring tools

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ICSE’2016 | Austin | May 19, 2016

Our goal

Help developers:1. Explore clone groups and understand

their relations2. Inspect and understand the differences

between clones

3. Refactor safely the clones

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ICSE’2016 | Austin | May 19, 2016

Clone Group Explorationfeatures

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Clone import

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Subclone information

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Clone filtering

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Clone monitoring

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Clone Pair Visualizationfeatures

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ICSE’2016 | Austin | May 19, 2016

Our approach

common

nesting trees

if (orientation == VERTICAL) { Line2D line = new Line2D.Double(); double x0 = dataArea.getMinX(); double x1 = dataArea.getMaxX(); g2.setPaint(im.getOutlinePaint()); g2.setStroke(im.getOutlineStroke());}

if (orientation == VERTICAL) { Line2D line = new Line2D.Double(); double x0 = dataArea.getMinX(); double x1 = dataArea.getMaxX(); g2.setPaint(im.getOutlinePaint()); g2.setStroke(im.getOutlineStroke());}else if(orientation == HORIZONTAL) { Line2D line = new Line2D.Double(); double y0 = dataArea.getMinY(); double y1 = dataArea.getMaxY(); g2.setPaint(im.getOutlinePaint()); g2.setStroke(im.getOutlineStroke());}

Detected clones

Control StructureMatching

PDGMapping

differences

unmappedstatements

PreconditionExamination

Refactorable clones

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Assessing the Refactorability of Software Clones, IEEE TSE, Nov. 2015

ICSE’2016 | Austin | May 19, 2016

Clone pair visualization

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Semantic tooltips

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ICSE’2016 | Austin | May 19, 2016

Renamed variables

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Clone Pair Refactoringfeatures

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Automatic clone refactoring

Based on the location of the clones, the best refactoring strategy is automatically determined

1. Extract Method (same file)

2. Pull Up Method (common superclass)a) Template Method (clones call local methods)b) Extract Superclass (external common superclass)

3. Introduce Utility Method (static clones)

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Refactoring Preview

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Future work

• Support multi-clone refactoring (>2 clones)

• Explore lambda expressions

• Automated refactoring engine testing

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Visit our project athttp://jdeodorant.org

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Advanced matches

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ICSE’2016 | Austin | May 19, 2016

Advanced matches

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