BarcelonaJUG2016: walkmod: how to run and design code transformations

walkmodhttp://www.walkmod.com-‐ twitter: @walkmod Raquel Pau (rpau@walkmod.com) Let’s start working with clean code! 1

A bit of me • Technical lead at Walkmod • Software engineer at Sparsity-‐Technologies • JavaCodeGeekswriter • Research publications about UML/OCL 2

First Law of Software Quality error = (more code)2 E = mc2 Moral: some errors always come back 3

Walkmod is for.. • Automatizing the resolution of problems detected by code quality tools • Automatizing the practice of code conventions in development teams (e.g create CRUD services) • Automatizing global code changes (e.g migrations) 7

and it is... • Open source (LGPL v3) – Discover what is happening with your code! – It is the result of contributions by people with the same needs. • Editor/ide independent – Command line interface – Maven/Gradle plugin 8

challenges • Automatic source code fixes must be applied without re-‐formatting • False-‐positives are not allowed • Plugins support for custom code conventions • Automatic software updates. 9

LET’S PLAY APPLYING WALKMOD IN GOOGLE/GUAVA 10

commands (1) • walkmod plugins • walkmod inspect ${pluginid} • walkmod add ${pluginid:transformationid} • walkmod apply / check 11

commands (2) • walkmod set-‐reader -‐d ${path} ${reader} • walkmod set-‐writer -‐d ${path} ${writer} • walkmod add-‐excludes ${file} • walkmod add-‐includes ${file} 12

google/guava results 501 java files in 113 sec ~ 4,4 files/sec 13

HOW IT WORKS FROM BOTTOM TO TOP 14

Execution Workflow 1. Parsing process 2. Semantic analysis 3. Run code transformations 4. Write the applied changes 15

parsing process CompilationUnit cu = ASTManager.parse( "public class Foo { "+ "public boolean test(int[] x[]) { "+ "return false;"+ " }"+ " } "); TypeDeclaration td = cu.getTypes().get(0); MethodDeclaration md = (MethodDeclaration) td.getMembers().get(0); 16

semantic analysis: type resolution • Resolves the java.lang.Class of every single expression “hello”.substring(1).indexOf(“o”) + 3 • Resolves the java.lang.Method of every single MethodCallExpression node. c. getEmployees().get(0) string string int int int com.foo.Company#getEmployees() java.util.List#get(int) 17

semantic analysis: definitions and references class MyClass { private int my_field; } class MyClass { private int myField; } All my_field references need to be updated! this.my_field = my_field; this.myField = my_field; 18

Semantic analysis: API • SymbolDataAware#getSymbolData() • SymbolDefinition#getUsages() • SymbolReference#getSymbolDefinition() • ScopeAware Interface for SymbolDefinition, SymbolReference & BlockStmt – #getVariableDefinitions() – #getTypeDefinitions() – #getMethodDefinitions() • Refactorizable#rename(String name) Interface for VariableDeclaration & Parameter. Applies safe updates to all the references to that variable/parameter. 19

semantic analysis: External symbol references RefactorConfigurationController #getMethodRefactorRules class MyClass { public int bar_(){} } class MyClass { public int bar(){} } {Foo:bar_() => Foo:bar()} 20

semantic analysis benefits • Ensures non false-‐positives J • Powerful transformations: – Remove dead code – Naming conventions / migrations – Class hierarchy queries 21

code transformations @RequiresSemanticAnalysys public class HelloVisitor extends VoidVisitorAdapter<VisitorContext> { ... @Override public void visit(MethodDeclaration md, VisitorContext ctx){ //TODO super.visit(md, ctx); } @Override public void visit(FieldDeclaration fd, VisitorContext ctx){ //TODO fd.getType().accept(this, ctx); } } 22

Semantic rules testing public class UseCollectionIsEmptyTest extends SemanticTest { @Test public void testEqualsToZero() throws Exception { CompilationUnit cu = compile( "import java.util.List; “+ ” public class Foo { “+ ”public boolean testIsEmpty(List list){“+ ” return list.size() == 0; }}"); UseCollectionIsEmpty visitor = new UseCollectionIsEmpty(); cu.accept(visitor, null); MethodDeclaration md = (MethodDeclaration) cu.getTypes() .get(0).getMembers().get(0); BlockStmt block = md.getBody(); ReturnStmt returnStmt = (ReturnStmt) block.getStmts().get(0); Assert.assertTrue(returnStmt.getExpr() instanceof MethodCallExpr); } } 23

writing the applied changes • eclipse-formatter (default): files are written using an eclipse formatter configuration. • javalang:string-writer: files are written applying the minimum change set. > walkmod set-writer ${writer} 24

CREATING A CODE CONVENTION TO FIX A SONAR RULE VIOLATION 25

General working procedure 1. Fork walkmod/walkmod-sonar-plugin 2. Git checkout master 3. Create a new visitor per rule 4. Create a test 5. Define it in the walkmod-sonar-plugin.xml 6. Create pull request 7. We deploy the changes under a new version to the maven repository 26

Let’s go to implement this rule 27

Local integration tests 1. Go to the walkmod-‐sonar-‐plugin directory 2. Execute mvn install 3. Replace jars: 1. Open the following directory: ${HOME}/.ivy2/cache/org.walkmod/walkmod-‐sonar-‐plugin/jars 2. Replace the jar that has the same name than walkmod-‐sonar-‐plugin/target/walkmod-‐sonar-‐plugin-‐${version}.jar 4. Run walkmod apply -‐-‐offline 28

ROADMAP TO IMPROVE THE USER EXPERIENCE 29

our roadmap is • More fine incremental execution • Report the changes introduced by each transformation. Why they appear? • Support more sonar/checkstyle/pmd rules ;) • Full integration with Intellij/eclipse/netbeans 30

and...walkmodhub • SaaS to run walkmod after: – Every push or pull request to Github – Incremental execution – Sends a pull request with the required changes • Get your clean code sticker! 31

THANKS Raquel Pau rpau@walkmod.com 32

BarcelonaJUG2016: walkmod: how to run and design code transformations

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