APIDiff: Detecting API Breaking Changes (SANER 2018, Tools Track)

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APIDiff: Detecting API Breaking Changes Aline Brito, Laerte Xavier, Andre Hora, Marco Tulio Valente SANER 2018, Tool Track

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Motivation Libraries have a key importance in modern software development 2

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Motivation Libraries have a key importance in modern software development 3

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Library services are provided via APIs 4

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In theory, APIs should be stable 5

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But, 28% out of 500K API changes break backward compatibility Historical and Impact Analysis of API Breaking Changes: A Large-Scale Study SANER, 2017 6

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Which changes break my code? How stable is this library? 7

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8 On the owner side… Write migration documents Identify and revert accidental breaking changes

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9 On the client side… Analyze the amount of breaking changes over time Select more stable libraries to depend on

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APIDiff Detecting API Breaking Changes

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11 APIDiff The tool analyses libraries available on git

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Catalog of Breaking and Non-breaking Changes detected by APIDiff

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Breaking Changes (BC) Changes performed in API elements that may break client applications 13 We exclude changes performed on deprecated API elements

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14 Element Breaking Changes (BC) Type REMOVE TYPE, LOST VISIBILITY, CHANGE IN SUPERTYPE, ADD FINAL MODIFIER, REMOVE STATIC MODIFIER, RENAME TYPE, MOVE TYPE Method REMOVE METHOD, LOST VISIBILITY, CHANGE IN RETURN TYPE, CHANGE IN PARAMETER LIST, CHANGE IN EXCEPTION LIST, ADD FINAL MODIFIER, REMOVE STATIC MODIFIER, MOVE METHOD, RENAME METHOD, PUSH DOWN METHOD, INLINE METHOD Field REMOVE FIELD, LOST VISIBILITY, CHANGE IN FIELD TYPE, CHANGE IN FIELD DEFAULT VALUE, ADD FINAL MODIFIER, MOVE FIELD, PUSH DOWN FIELD

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Example: Change in Access Modifiers 15 public int M1(String){ ... } private int M1(String){ ... }

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Example: Change in Parameter List 16 public int M1(Context){ ... } public int M1(){ ... }

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Example: Element Removal 17 public class C1{ ... } public class C1{ ... }

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Example: Refactoring Operations 18 public int M1(String, Integer){ ... } public int M2(String, Integer){ ... }

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Non-breaking Changes (NBC) Changes that do not break clients 19

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20 Element Non-Breaking Changes (NBC) Type ADD TYPE, GAIN VISIBILITY, REMOVE FINAL MODIFIER, ADD STATIC MODIFIER, ADD SUPERTYPE, EXTRACT SUPERTYPE, DEPRECATED TYPE Method ADD METHOD, PULL UP METHOD, GAIN VISIBILITY, REMOVE FINAL MODIFIER, ADD STATIC MODIFIER, DEPRECATED METHOD, EXTRACT METHOD Field ADD FIELD, PULL UP FIELD, GAIN VISIBILITY, REMOVE FINAL MODIFIER, DEPRECATED FIELD

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Example: Change in Access Modifiers 21 private int M1(String){ ... } public int M1(String){ ... }

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Example: Add Element 22 public class C1{ public void M1(){ … } } public class C1{ }

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Examples 23

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24 An image loading and caching library 20K stars A framework to implement unit tests 6K stars

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Example 1: Detecting Changes in Version Histories 25

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26 Detecting Changes in Version Histories Useful to analyze several commits at once Useful to assess libraries stability

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Detecting Changes in Version Histories 27 APIDiff diff = new APIDiff( “bumptech/glide”, “https://github.com/bumptech/glide.git”); Result result = diff.detectChangeAllHistory(“master”, Classifier.API);

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Detecting Changes in Version Histories 28 APIDiff diff = new APIDiff( “bumptech/glide”, “https://github.com/bumptech/glide.git”); Result result = diff.detectChangeAllHistory(“master”, Classifier.API);

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Example 2: Fetching New Commits 29

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30 Fetching New Commits Useful to monitor changes in a repository Contributors are notified shortly after BCs are introduced

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Fetching New Commits 31 APIDiff diff = new APIDiff( “bumptech/glide”, “https://github.com/bumptech/glide.git”); Result result = diff.fetchAndDetectChange(Classifier.API);

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Fetching New Commits 32 APIDiff diff = new APIDiff( “bumptech/glide”, “https://github.com/bumptech/glide.git”); Result result = diff.fetchAndDetectChange(Classifier.API);

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Example 3: Detecting Changes in Specific Commits 33

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34 Detecting Changes in Specific Commits Useful to analyze pull requests Useful to detect accidental BCs

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Detecting Changes in Specific Commits 35 APIDiff diff = new APIDiff( “mockito/mockito”, “https://github.com/mockito/mockito.git”); Result result = diff.detectChangeAtCommit( "4ad5fdc14ca4b979155d10dcea0182c82380aefa", Classifier.API);

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Detecting Changes in Specific Commits 36 APIDiff diff = new APIDiff( “mockito/mockito”, “https://github.com/mockito/mockito.git”); Result result = diff.detectChangeAtCommit( "4ad5fdc14ca4b979155d10dcea0182c82380aefa", Classifier.API);

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Detecting Changes in Specific Commits 37 APIDiff diff = new APIDiff( “mockito/mockito”, “https://github.com/mockito/mockito.git”); Result result = diff.detectChangeAtCommit( "4ad5fdc14ca4b979155d10dcea0182c82380aefa", Classifier.API); Category: Add Method Description: Method answersWithDelay(long, Answer) added in class org.mockito.AdditionalAnswers

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Result Type 38 - category : String - description : String - path : String - element : String - javadoc : Boolean - deprecated : Boolean - breakingChange : Boolean - revCommit: RevCommit Change

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Example 4: Filtering Packages 39

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40 Filtering Packages It is also possible to filter in/out packages Useful to detect changes in internal implementations

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Filtering Packages 41 Result result = diff.detectChangeAtCommit( "4ad5fdc14ca4b979155d10dcea0182c82380aefa", Classifier.API);

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Architecture

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44 Processing Module ● Git operations ● Instances library

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45 Refactoring Module detects refactoring actions (reused from RefDiff) RefDiff: Detecting Refactorings in Version Histories Danilo Silva, Marco Tulio Valente - MSR, 2017

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46 Analysis Module detects the changes in the library history

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Future Work 47

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Future Work 48 ● Evaluate the precision of APIDiff ● Support to other programming languages ● Feature to analyze changes at release level

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https://github.com/aserg-ufmg/apidiff 49

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Thank you! Aline Brito, Laerte Xavier, Andre Hora, Marco Tulio Valente SANER 2018, Tool Track