walkmodhttp://www.walkmod.com-­‐ twitter:  @walkmod

Raquel  Pau  (rpau@walkmod.com)

Let’s  start  working  with  clean  code!

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A bit of me

• Technical  lead  at  Walkmod

• Software  engineer  at  Sparsity-­‐Technologies

• JavaCodeGeekswriter

• Research  publications  about  UML/OCL

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First Law of Software Quality

error  =  (more  code)2E  =  mc2

Moral: some errors always come back

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Ok, we need some help…

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Really?

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Developers principle

DRY6

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.gmigrations)

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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

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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.

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LET’S PLAYAPPLYING WALKMOD IN GOOGLE/GUAVA

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commands (1)

• walkmod  plugins

• walkmod  inspect  ${pluginid}

• walkmod  add  ${pluginid:transformationid}

• walkmod  apply  /  check

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commands (2)

• walkmod  set-­‐reader  -­‐d  ${path}  ${reader}

• walkmod  set-­‐writer  -­‐d  ${path}  ${writer}

• walkmod  add-­‐excludes  ${file}

• walkmod  add-­‐includes  ${file}

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google/guava results

501  java  files  in  113  sec  ~  4,4  files/sec

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HOW  IT  WORKSFROM BOTTOM TO TOP

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Execution Workflow

1. Parsing  process  2. Semantic  analysis  3. Run  code  transformations4. Write  the  applied  changes

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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);

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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;

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Semantic analysis:API

• SymbolDataAware#getSymbolData()

• SymbolDefinition#getUsages()• SymbolReference#getSymbolDefinition()

• ScopeAwareInterface  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.

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semantic analysis:External symbol references

RefactorConfigurationController#getMethodRefactorRules

class MyClass {public int bar_(){}

}

class MyClass {public int bar(){}

}

{Foo:bar_() => Foo:bar()}

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semantic analysis benefits

• Ensures  non  false-­‐positives  J

• Powerful  transformations:– Remove  dead  code– Naming  conventions  /  migrations– Class  hierarchy  queries

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code transformations

@RequiresSemanticAnalysyspublic class HelloVisitor   extendsVoidVisitorAdapter<VisitorContext>   {...@Overridepublic void visit(MethodDeclaration  md,  VisitorContext  ctx){//TODOsuper.visit(md,   ctx);

}

@Overridepublic void visit(FieldDeclaration   fd,  VisitorContext  ctx){//TODOfd.getType().accept(this,   ctx);

}

}  

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Semantic rules testing

public class UseCollectionIsEmptyTest extends SemanticTest {

@Testpublic 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);}

}

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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}

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CREATING  A  CODE  CONVENTIONTO FIX A SONAR RULE VIOLATION

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General working procedure

1. Fork  walkmod/walkmod-sonar-plugin

2. Git checkout  master3. Create  a  new  visitor  per  rule4. Create  a  test5. Define  it  in  the  walkmod-sonar-plugin.xml

6. Create  pull  request7. We  deploy  the  changes  under  a  new  version  

to  the  maven  repository

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Let’s go to implement this rule

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Local integration tests

1. Go  to  the  walkmod-­‐sonar-­‐plugin  directory2. Execute  mvn install3. 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

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ROADMAPTO IMPROVE THE USER EXPERIENCE

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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

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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!

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THANKS

Raquel  Pau  rpau@walkmod.com

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