Modern Refactoring II Escola de Informtica Terica e Mtodos Formais - - PowerPoint PPT Presentation
Modern Refactoring II Escola de Informtica Terica e Mtodos Formais Volker Stolz 1 , Larissa Braz 2 , Anna M. Eilertsen 3, Fernando Macas 1 , Rohit Gheyi 2 Western Norway University of Applied Sciences, Universidade Federal de
Volker Stolz1, Larissa Braz2, Anna M. Eilertsen3, Fernando Macías1, Rohit Gheyi2
Supported by the bilateral SIU/CAPES project “Modern Refactoring” 2017/18
Western Norway University of Applied Sciences, Universidade Federal de Campina Grande, University of Bergen, Norway
II Escola de Informática Teórica e Métodos Formais
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(Everybody’s doing it; you should as well!)
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“A change made to the internal structure of software to make it easier to understand and cheaper to modify without changing its observable behaviour” [Fowler]
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Motivation:
From mathematical term “factor”: finding multiple occurrences of similar code and factoring it into a single reusable function
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with quicksort still a refactoring?
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action from menu.
the Abstract Syntax Tree (AST) in memory…
source code file.
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declared? What are the superclasses?)
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[Roberts, Brant, Johnson ’97]
[Fowler ’99]
[Murphy et al., 2006]
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Refactoring: Improving the Design of Existing Code Martin Fowler with Kent Beck, John Brant, William Opdyke, Jon Roberts Addison Wesley, 1999
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automated changes
when they can predict changes
refactoring touches on multiple contexts
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The agile workflow
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than 300 engineers who had used refactoring during Microsoft Windows development
2009
refactoring, but they see costs and risks as well.
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Software” [Gamma, Helm, Johnson, Vlissides, 1994]
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indicators of design deficiencies
repeated code (CS), long functions (CS)
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cyclometric complexity…
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identify problems
“competing” against each other
based composed refactorings”, NIK 2014
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“Source Code Rejuvenation” [Pirkelbauer, Dechev, Stroustrup ’10]
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From: Pirkelbauer, Dechev, Stroustrup, SOFSEM 2010
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vector<int> vec; // three consecutive push backs vec.push_back(1); vec.push_back(2); vec.push_back(3); // copying from an array int a[] = {1, 2, 3}; vector<int> vec(a,a+sizeof(a)/sizeof(int)); // rejuvenated source code in C++0x vector<int> vec = {1, 2, 3};
Inefficient! Sizeof() what again?! Now isn’t that pretty:
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…
(semantical overlap with OO-refactoring)
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Encapsulate Field: avoid direct field access 1) introduce setter & getter methods; 2) replace all field accesses with calls to new methods; 3) make field private.
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Right-click on a field and find the “Refactor” menu.
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IDEs will often have a helpful dialog, because further input is required.
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Enjoy your result!
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IDEs will even try to be helpful!
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Encapsulate Field: avoid direct field access 1) introduce setter & getter methods; 2) replace all field accesses with calls to new methods; 3) make field private. Let’s assume you have to program this refactoring. Can you see what happens if you swap steps 2 & 3? We will come back later to that.
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Compute complex (expensive) expression only once.
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Fowler has a pretty loooong list of refactorings in his book:
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https://refactoring.com/catalog/
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checkInitialConditions()
script
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special challenges…
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showed up in 1984
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[1] W. Opdyke, “Refactoring Object-Oriented frameworks,” Ph.D. dissertation, University of Illinois at Urbana-Champaign, 1992.
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Remember how you studied logic in your first year?
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grammar but also preprocessor directives
depending on the value of conditions evaluated during compilation.
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#ifdef A int x = 0; #else int x = 1; #endif
Code before preprocessing
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and outputs pure C code, where directives have been stripped out and substituted accordingly:
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#ifdef A int x = 0; #else int x = 1; #endif int x = 0; int x = 1;
Code after preprocessing Code before preprocessing A is enabled A is disabled
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disadvantages:
may no longer apply.
unmaintainable.
International Workshop on Principles of Software Evolution. ACM, 6–14.
Evolution and Process 25, 12 (2013), 1285–1304. 38
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Disciplined vs undisciplined conditional annotations
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#ifdef A int x = 0; #else int x = 1; #endif int x = #ifdef A 0; #else 1; #endif
Undisciplined Disciplined
(Don’t write that code!)
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F . Medeiros, M. Ribeiro, R. Gheyi, S. Apel, C. Kästner, B. Ferreira, L. Carvalho, and B. Fonseca: Discipline Matters: Refactoring of Preprocessor Directives in the #ifdef Hell. Transactions on Software Engineering (2017). To appear.
Refactoring improves code quality
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e.g. during Continuous Integration
(e.g. through ticketing system)
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Wright et al., ICSM 2013.
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new strings::Split() API
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https://www.youtube.com/watch?v=mVbDzTM21BQ
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“A change made to the internal structure of software to make it easier to understand and cheaper to modify without changing its observable behaviour” [Fowler] Challenge: Can we predict the effect of applying a refactoring?
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Output: 1735600054 ← Method n() called on two different objects 21685669
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Output now: 1735600054 ← Method n() called on the same object! 1735600054 (changed behaviour)
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Output now: 1735600054 Exception in thread ”main” java.lang.AssertionError
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parameter instead of this!
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be subjected to additional tests
→ less likely to discover fault
→ better chances of discovery
[Alves et al., 2017: Test coverage of impacted code elements for detecting refactoring faults: An exploratory study]
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implemented)
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Implemented through JastAdd meta-compilation system
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Analyzing Refactorings on Software Repositories
difference detected between source and target programs
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Average of: refactoring frequency, granularity, scope, and test coverage
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Soares et al.: Analyzing Refactorings on Software Repositories
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UML diagrams.
source, but an intermediate representation. Example: class diagram derived from Java code.
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(e.g. UML) and domain-specific modelling languages
(reverse engineering and modernisation)
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process (horseshoe)
Source: Erik Philippus
transformations
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dependencies
using graph transformation." Software and Systems Modeling, 2007
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EMF Refactor
class diagrams (Ecore metamodels)
for any EMF-based model
Source: eclipse.org
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refactoring using a model transformation engine”, 2005
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Mantz et al. “Co-evolving meta-models and their instance models: A formal approach based on graph transformation”, 2015
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[Li et al., Interactive Transformations from Object- Oriented Models to Component-Based Models]
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to describe transformations
→ complex transformations
instance of refactoring correct (with proof obligations)
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important software engineering topic.
refactoring always needs improvement.
& semantics, grammars & parsing, ASTs, typing rules)
also useful for security analysis)
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Foundations:
. Opdyke. Refactoring object-oriented frameworks. Technical Report GAX93-05645, University of Illinois at Urbana-Champaign, 1992.
3(4):253–263, 1997.
Software”, 1994
Evolution, 20(5):345–364, 2008.
. Pirkelbauer, D. Dechev, B. Stroustrup: Source Code Rejuvenation Is Not Refactoring. SOFSEM 2010
Foundations of Softw. Eng. ACM, 2010
23(4), 2006.
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“Modern” Reading:
. Bailey, and R. E. Johnson. Use, disuse, and misuse of automated refactorings. In 34th Intl. Conf. on Software Engineering (ICSE 2012). IEEE, 2012.
. Black. How we refactor, and how we know it. Software Engineering, IEEE Transactions on, 38(1):5–18, 2012.
. Steimann. Refactoring tools are trustworthy enough and trust must be earned. IEEE Software, 32:80– 83, 2015.
SBES 2011
. Borba. Making refactoring safer through impact analysis. SCP , 93:39–64, 2014.
Systems Modeling, 6(3):269–285, 2007.
Languages, and Applications (OOPSLA) ’10. ACM, 2010.
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. Medeiros, M. Ribeiro, R. Gheyi, S. Apel, C. Kästner, B. Ferreira, L. Carvalho, and B. Fonseca: Discipline Matters: Refactoring of Preprocessor Directives in the #ifdef Hell. Transactions on Software Engineering (2017).
5th International Workshop on Principles of Software Evolution. ACM, 6–14.
Software: Evolution and Process 25, 12 (2013), 1285–1304.
.D. de Lima Machado: Test coverage of impacted code elements for detecting refactoring faults: An exploratory study. J. Systems and Software 123, 2017.
Component-Based Models. FACS 2011, LNCS, Springer 2011.
. Mantz, et al.: Co-evolving meta-models and their instance models: A formal approach based on graph transformation. Science of Computer Programming 104 (2015): 2-43.
transformation engine. Model-driven Software Development 23 (2005).
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