Source code diff revolution 

How are developers reviewing code? 

A screenshot of a computer Description automatically generated 

Eugene Myers Language independent Super-fast and scalable Does not handle well moves 

Abstract Syntax Tree diff Fine-grained diff between AST nodes (not just lines) Supports moves and updates (not just additions and deletions) Still has limitations (coming up soon…) 

A screenshot of a computer Description automatically generated 

2007 Change Distiller Fluri et al. 2014 GumTree Falleri et al. 2016 MTDiff Dotzler et al. 2018 IJM Frick et al. 2023 iASTMapper Zhang et al. 2024 RMiner 3 Alikhanifard et al. Language aware Partial matching Language independent Largest identical subtrees Language independent Move action optimizations Tree Matching Statement Mapping 

No support for multi-mappings Limitation #1 “A given node can only belong to one mapping” 

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GumTree Simple 

GumTree Greedy 

RefactoringMiner calls to extracted method 

Incorrect matching of program declarations Limitation #2 “The algorithm is independent of any language specificity” 

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GumTree Simple renamed new method 

RefactoringMiner call to extracted method 

Semantic ignorance Limitation #3 “Mappings involve two nodes with identical labels” 

GumTree Greedy Type matched with variable Variable matched with method call Variable matched with lambda parameter For body block matched with method body block 

RefactoringMiner 

Refactoring un-awareness Limitation #4 

GumTree Simple RefactoringMiner Rename object to item Extract variable itemKey object matched with itemKey object matched with item 

No support for commit-level analysis Limitation #5 

GumTree Greedy 

RefactoringMiner Pulled up to superclass AbstractDQLPlanNode Moved from class NestedLoop 

Poor evaluation standards Limitation #6 

Is shorter (edit script) better? 

The path of Virtue or Vice Bench marks shorter edit script 

AST Diff benchmark • Process (6 months): 1. Run all ASTDiff tools (GumTree 3.0, GumTree 2.1, IJM, MTDiff, RMiner) 2. Manually validate the diffs 3. Construct the “perfect” diff • Datasets: • 800 bug fixings commits from Defects4J • 187 refactoring commits from Refactoring Oracle 

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Approach 

RefactoringMiner Statement mappings Program declaration mappings Import declaration mappings Refactoring mappings based on mechanics Tree Matcher Tree Matcher Overwrite conflicting mappings AST mappings AST mappings Final AST mappings Edit script version1 version2 

Evaluation results 

AST mapping accuracy dataset RMiner 3 Precision Recall GumTree greedy Precision Recall GumTree simple Precision Recall iASTMapper Precision Recall Defects4J 99.7 99.3 97.5 93.1 98.4 97.8 98.5 99 Refactoring 99.6 99.2 84.1 70.2 86.7 72.4 91.8 79.2 Overall 99.7 99.3 93.8 86.1 95.2 90 96.7 92.9 1. RMiner 3.0 99.5% 2. iASTMapper 94.8% 3. GumTree simple 92.6% 4. GumTree greedy 89.8% Tree Matching Statement Mapping Ranking based on F-score ±1-6% ±8-29% 99.4% 85.0% 78.9% 76.5% Refactoring only 

How can I use your tool? 1. dependency 2. Command line tool 3. Docker image 4. git rmd APIs: 1. With a commit of a locally cloned git repository 2. With a commit fetched directly from GitHub 3. With the files changed in a GitHub Pull Request 4. With two directories https://github.com/tsantalis/RefactoringMiner 

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File split to multiple files 

Code from different files merged to a single file 

https://github.com/tsantalis/RefactoringMiner https://github.com/pouryafard75/DiffBenchmark