Guide Refactorings With Behavioral Code Analysis @AdamTornhill craft-conf.com 

Modify someone else’s C++ code The Human Potential Hard Impossible Land on the Moon Sequence the Human Genome Revive the Dinosaurs The Pyramids Fusion Power Understand Consciousness @AdamTornhill 

Lehman’s “Laws” of Software Evolution Continuing Change “a system must be continually adapted or it becomes progressively less satisfactory” @AdamTornhill Increasing Complexity “as a system evolves, its complexity increases unless work is done to maintain or reduce it” M. Lehman, “Programs, life cycles, and laws of software evolution”, 1980 

The Two Forms Of Accidental Complexity Complex Parts Complex Inter-Dependencies @AdamTornhill 

Behavioral Code Analysis - What Is It? Code: Important Evolution and Behavior: More Important @AdamTornhill 

Version-Control: A Behavioral Data Source Commit: b557ca5 Date: 2016-02-12 Author: Kevin Flynn Fix behavior of StartsWithPrefix 8 27 src/Mvc.Abstractions/ModelBinding/ModelStateDictionary.cs 1 10 src/Mvc.Core/ControllerBase.cs 1 1 src/Mvc.Core/Internal/ElementalValueProvider.cs 1 39 src/Mvc.Core/Internal/PrefixContainer.cs Commit: fd6d28d Date 2016-02-10 Author: Professor Falken Make AddController not overwrite existing IControllerTypeProvider 8 1 src/Core/Internal/ControllersAsServices.cs 48 0 test/Core.Test/Internal/ControllerAsServicesTest.cs 13 0 test/Mvc.FunctionalTests/ControllerFromServicesTests.cs Commit: 910f013 Date :2016-02-05 Author Lisbeth Salander Fixes #4050: Throw an exception when media types are empty. 20 1 src/Mvc.Core/Formatters/InputFormatter.cs Social Information A Time Dimension Progress on Tasks Co-changing Files @AdamTornhill 

Prefer Simple Metrics Metrics are a Guide, not a Replacement for Expertise because @AdamTornhill 

Extract The Signal via a Human in the Loop View Complexity Through the Lens of Behavioral Data 

Case Study: Android The Platform Framework Base in Numbers 3 Million Lines of Code 2,1 Million Lines of Java 2,000 Unique Authors @AdamTornhill 

Case Study: Android The Platform Framework Base in Numbers 3 Million Lines of Code 2,1 Million Lines of Java 2,000 Unique Authors @AdamTornhill 

Case Study: Android Code Complexity Code Change Frequency Hotspot @AdamTornhill 

What we normally care about… A simpler view! Ref to Python script… What’s Code Complexity Anyway? Implementation: https://github.com/adamtornhill/maat-scripts/blob/master/miner/complexity_analysis.py @AdamTornhill 

Case Study: Android 20,097 Lines of Code 2,009 Commits 

Trade-Offs: Improvements vs New Features 

Programming As If Social Factors Mattered Author #1 Author #2 Author #N The Relative Contributions of Each Author contributors Fractal Value: M. D’Ambros, M. Lanza, and H Gall. Fractal Figures: Visualizing Development Effort for CVS Entities. 

The Splinter Pattern The splinter pattern provides a structured way to break up hotspots into manageable pieces that can be divided among several developers to work on, rather than having a group of developers work on one large piece of code. https://pragprog.com/book/atevol/software-design-x-rays 

ActivityStack.java Translucence.java DeviceOwnership.java ActivityLifecycle.java delegate delegate delegate Stack behavior Translucence 
 behavior Ownership 
 behavior Lifecycle behavior Splinter Context Original Context The Splinter Pattern Unmodified, copy-pasted (yes, really) content @AdamTornhill 

Splinter: Resulting Context ActivityStack.java Translucence.java DeviceOwnership.java ActivityLifecycle.java Better alignment between problem and solution domain 
 => facilitates parallel work Individual Parts that can be refactored in isolation @AdamTornhill 

ActivityStack.java @AdamTornhill Cut The Middle Man 

Measure and Visualize Improvements The effects of a Splinter refactoring @AdamTornhill 

Methods and Functions: Where Do We Start? @AdamTornhill 

Function Level Hotspots Parse Recommended functions to improve. Hotspots: X-Ray ActivityManagerService.java @AdamTornhill 

X-Ray of ActivityManagerService.java @AdamTornhill 

https://codescene.io/ Source Code: 
 https://github.com/adamtornhill/code-maat Tooling: Try it on your own Code Track functions with git log -L :: @AdamTornhill 

Code Duplication and DRY Violations 5-20% of all Code is Duplicated to Some Extent @AdamTornhill 

@AdamTornhill DRY Violations in handleMessage (Andoid) 

@AdamTornhill DRY Violations in handleMessage (Andoid) Next refactoring step: Design Pattern COMMAND? 

@AdamTornhill The Dirty Secret of Copy Paste Image from https://en.wikipedia.org/wiki/Rorschach_test 

B() A() Change Coupling: Patterns That Emerge Over Time Commit #1 Commit #2 E() Commit #3 Changed code B() A() Changed code 

Case Study: Code Clones in Linux @AdamTornhill The Linux Kernel in Numbers 16 Million Lines of Code 15 Million Lines of C 15,000 Unique Authors 

Inside the Main Hotspot: intel_display.c 11,383 Lines of Code 3,040 Commits 

Inside The Main Hotspot: intel_display.c 11,383 Lines of Code 3,040 Commits 

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Inside the Main Hotspot: intel_display.c 11,383 Lines of Code 3,040 Commits 

A bug due to omission? A context-specific check? 

Combine copy-paste Detection techniques with change coupling to identify the code clones that really need refactoring. Clone Detector Applications Clone Digger (Java and Python): http://clonedigger.sourceforge.net/
 Simian (.NET): http://www.harukizaemon.com/simian/ @AdamTornhill 

Duplication goes Beyond Code Similarity @AdamTornhill 

Case Study: Refactoring Entity Framework Core @AdamTornhill Entity Framework Core in Numbers 574,000 Lines of Code 365,000 Lines of C# 102 Unique Authors 

Code Clones in Entity Framework - Refactor? 

The Principle of Proximity 

The Principle of Proximity in Code @AdamTornhill 

The Proximity Refactoring 

Image from https://thedailywtf.com/articles/comments/Enterprise-Dependency-Big-Ball-of-Yarn Reducing Complex Inter-Dependencies 

Image from https://thedailywtf.com/articles/comments/Enterprise-Dependency-Big-Ball-of-Yarn The Heuristic of Surprise 

Case Study: jUnit5 @AdamTornhill jUnit5 in Numbers 59,000 Lines of Code 51,000 Lines of Java 74 Unique Authors 

Unit tests that change together in ~70% of all commits @AdamTornhill 

X-Ray of the Coevolving jUnit Tests @AdamTornhill 

Let’s Look at the Code… ExceptionHandlingTests.java ReportingTests.java TestCaseWithInheritanceTests.java @AdamTornhill 

Refactoring jUnit: Express Our Domain 

Refactoring jUnit: Express Our Domain 

Express Tests in the Language of your Domain; Generic Assertions are at Odds with that Goal. @AdamTornhill 

The Costs of Implicit Dependencies Increase with Architectural Distance @AdamTornhill 

UI code implemented in JavaScript… …changed coupled to backend code implemented in Clojure (different repository) @AdamTornhill 

Git Repository Analysis Engine Backend UI Data Mining Git Repository Git Repository Change Coupling! 

How Can You Track Changes Across Repositories? @AdamTornhill e9e57e48 2017-05-26 D.Cooper [email protected] 
 Bugfix: the owls are not what they seem. Task: CLJ-2141 A specific commit Use a Task ID or Ticket Reference 

UI code implemented in JavaScript… …changed coupled to backend code implemented in Clojure (different repository) @AdamTornhill 

X-Ray Across Repository Boundaries JavaScript function… …that changes with Clojure business logic. @AdamTornhill 

Let Features Drive Architectural Building Blocks, not Technology. @AdamTornhill 

@AdamTornhill Blog on Behavioral Code Analysis http://www.empear.com/blog/ Your Code As A Crime Scene https://pragprog.com/book/atcrime/your-code-as-a-crime-scene Software Design X-Rays https://pragprog.com/book/atevol/software-design-x-rays Test the Analyses in CodeScene: https://codescene.io/ [email protected]