- The document describes an approach called ChangeCommander for recommending context changes to method invocations based on patterns learned from past context changes that fixed bugs. - An initial validation of the approach on five open source projects showed it was able to recommend true positive context changes that later fixed bugs, with a varying number of false positive and false negative recommendations depending on the project. - The goal of the ChangeCommander approach is to integrate recommendations into the development process to potentially reduce future bugs.

1. ChangeCommander
Recommending Method Invocation
Context Changes
Beat Fluri, Jonas Zuberbühler, and Harald C. Gall
s.e.a.l. - software evolution & architecture lab
Department of Informatics
University of Zurich, Switzerland
University of Zurich
Department of Informatics software evolution & architecture lab

2. Which changes fix bugs?
Bug fix change study on Eclipse
43 plugins from Platform, JDT, and PDE
15% of bugs fixes contain context changes
of method invocation statements

3. Which changes fix bugs?
Bug fix change study on Eclipse
43 plugins from Platform, JDT, and PDE
15% of bugs fixes contain context changes
of method invocation statements
Method Invocation Context Change
Moving a method invocation into the
then or the else-part of an if-statement.

4. Which changes fix bugs?
Bug fix change study on Eclipse
43 plugins from Platform, JDT, and PDE
visited.add(outputFolder);
15% of bugs fixes contain context changes
of method invocation statements
Method Invocation Context Change
Moving a method invocation into the
then or the else-part of an if-statement.

5. Which changes fix bugs?
Bug fix change study on Eclipse
43 pluginsif (!visited.contains(outputFolder)) {
from Platform, JDT, and PDE
visited.add(outputFolder);
15% of bugs fixes contain context changes
of method invocation statements
}
Method Invocation Context Change
Moving a method invocation into the
then or the else-part of an if-statement.

6. Context changes tend to be similar
Similar conditions for all methods
Similar conditions for specific methods

7. Context changes tend to be similar
Similar conditions for all methods
if (myObject != null) { if (list != null) {
list.add(myObject); list.add(myObject);
} }
Similar conditions for specific methods

8. Context changes tend to be similar
Similar conditions for all methods
if (myObject != null) { if (list != null) {
list.add(myObject); list.add(myObject);
} }
Similar conditions for specific methods
if (!list.contains(myObject)) {
list.add(myObject);
}

9. Pattern extraction process

10. Pattern extraction process
Context
changes

11. Pattern extraction process
Context
changes

12. Pattern extraction process
Context
changes

13. Pattern extraction process
Context Invocation
changes aggregation

14. Pattern extraction process
Context Invocation Pattern
changes aggregation extraction

15. Pattern extraction process
Context Invocation Pattern
changes aggregation extraction

16. Invocation aggregation
Method invocations Invocation signature
list.add(myObject) java.util.List.add(MyClass)

17. Invocation aggregation
Method invocations Invocation signature
list.add(myObject) java.util.List.add(MyClass)

18. Invocation aggregation
Method invocations Invocation signature
list.add(myObject) java.util.List.add(MyClass)

19. Invocation aggregation
Method invocation Invocation signature
list.add(anObject) java.util.List.add(MyClass)

20. Invocation aggregation
Method invocation Invocation signature
list.add(anObject) java.util.List.add(MyClass)
Same Package

21. Invocation aggregation
Method invocation Invocation signature
list.add(anObject) java.util.List.add(MyClass)
Same Package
Imports

22. Invocation aggregation
Method invocation Invocation signature
list.add(anObject) java.util.List.add(MyClass)
JDT
Same Package
Imports

23. Invocation aggregation
Method invocation Invocation signature
list.add(anObject) java.util.List.add(MyClass)
JDT
Same Package
Imports

24. Invocation aggregation
Method invocation Invocation signature
list.add(anObject) java.util.List.add(MyClass)
Post Resolver
JDT
Match in scope
variables
Match in imports
...
Same Package
Imports

25. Invocation aggregation
Method invocation Invocation signature
list.add(anObject) java.util.List.add(MyClass)
Post Resolver
JDT
Match in scope
variables
Match in imports
...
Same Package
Imports

26. Pattern extraction
Aggregated invocations Context change patterns
list != null && <qualifier> != null
!list.contains(myObject) !<qualifier>.contains(<argument_0>)
list.add(myObject)

27. Pattern extraction
Aggregated invocations Context change patterns
list != null && <qualifier> != null
!list.contains(myObject) !<qualifier>.contains(<argument_0>)
list.add(myObject)

28. Pattern extraction
Aggregated invocations Context change patterns
list != null && <qualifier> != null
!list.contains(myObject) !<qualifier>.contains(<argument_0>)
list.add(myObject)

29. Pattern extraction
Aggregated invocations Context change patterns
list != null && <qualifier> != null
!list.contains(myObject)
!<qualifier>.contains(<argument_0>)
Split compound
conditions into
single conditions

30. Pattern extraction
Aggregated invocations Context change patterns
list != null && <qualifier> != null
!list.contains(myObject)
!<qualifier>.contains(<argument_0>)
Split compound
conditions into Token streams for
single conditions - conditions
- method invocation

31. Pattern extraction
Aggregated invocations Context change patterns
list != null && <qualifier> != null
!list.contains(myObject)
!<qualifier>.contains(<argument_0>)
Split compound
conditions into Token streams for
single conditions - conditions
- method invocation

32. Pattern extraction
Aggregated invocations Context change patterns
list != null && <qualifier> != null
!list.contains(myObject)
!<qualifier>.contains(<argument_0>)
Split compound
conditions into Token streams for
single conditions - conditions
- method invocation
list.add(myObject)

33. Pattern extraction
Aggregated invocations Context change patterns
list != null && <qualifier> != null
!list.contains(myObject)
!<qualifier>.contains(<argument_0>)
Split compound
conditions into Token streams for
single conditions - conditions
- method invocation
list.add(myObject)

34. Pattern extraction
Aggregated invocations Context change patterns
list != null && <qualifier> != null
!list.contains(myObject)
!<qualifier>.contains(<argument_0>)
Split compound
conditions into Token streams for
single conditions - conditions
- method invocation
list.add(myObject)

35. Recommendation

36. Recommendation

37. Recommendation

38. Recommendation
java.util.List.add(MyClass)

39. Recommendation
java.util.List.add(MyClass)

40. Recommendation
java.util.List.add(MyClass)

41. Recommendation
java.util.List.add(MyClass)
x
x
Surrounding if
already contains
condition
Filter predefined
method
invocations

42. Recommendation
java.util.List.add(MyClass)
x
x
Surrounding if
already contains
condition
Filter predefined
method
invocations

43. ChangeCommander

44. A first validation
Split history
Training set: Past context changes up to a
certain release
Test set: Context changes after that
particular release
Recommended context change
True positive (TP): in test set
False positive (FP): not in test set
False negative (FN): context change in test set but not recommended

45. A first validation
Project TP #B FP FN
ArgoUML 29 11 4675 75
Azureus 15 3 - 82
Eclipse JDT 51 27 - 158
Eclipse PDE 35 25 8011 46
jEdit 1 0 1307 13

46. A first validation
Project TP #B FP FN
ArgoUML 29 11 4675 75
Azureus 15 3 - 82
Eclipse JDT 51 27 - 158
Eclipse PDE 35 25 8011 46
jEdit 1 0 1307 13

47. Conclusions
Recommending context changes
We leverages context change data to
suggest corresponding modifications on
existing or newly added method
invocations.
ChangeCommander
By integrating our recommendation
approach into the development
process, we aim at reducing future
bugs.