Code comments support developers in understanding and maintaining codebases. Specifically in the Pharo environment, code comments serve as the main form of code documentation and usually convey information ranging from high-level design descriptions to low-level implementation details. Nevertheless, numerous important classes in Pharo still lack comments as developers find writing comments to be a tedious and effort-intensive task. Previous works in Java have recommended generating comments automatically to reduce commenting effort and save developers time. There exist several approaches to achieve this goal. One such popular approach is based on identifying stereotypes, i.e., a generalized set of characteristics supposed to represent an entity (object, class). However, this approach has not been tested for other programming languages. In this paper, we adopt the stereotype-based approach to automatically generate class comments in the Pharo programming environment.

1. Can We Automatically Generate Class
Comments in Pharo?
Pooja Rani, Alexandre Bergel,
Lino Hess, Timo Kehrer, Oscar Nierstrasz
University of Bern, Switzerland
International Workshop on Smalltalk Technologies,
Novi Sad, Serbia, 2022

2. 2

3. 3
High-quality code comments assist developers

4. 4
Developers find writing comments a boring and effort-intensive task

5. 5
To support developers in writing comments,
communities suggest coding guidelines
Apache
Oracle
Google Pharo
PEP8/257

6. 6
To support developers in writing comments,
communities suggest coding guidelines
Apache
Oracle
Google Pharo
PEP8/257

7. 7
To support developers in writing comments,
communities suggest coding guidelines
Apache
Oracle
Google Pharo
PEP8/257

8. 8
To support developers in writing comments,
communities suggest coding guidelines
Apache
Oracle
Google Pharo
PEP8/257

9. 9
- Rani et al., Empirical Software Engineering, 2021
Developers follow template inspired information types more often
To support developers in writing comments,
communities suggest coding guidelines
Apache
Oracle
Google Pharo
PEP8/257

10. 10
Color scale according to number of comments falling into a category
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Categories
Pharo
versions
(total
classes)
Developers follow template inspired information types more often
- Rani et al., Empirical Software Engineering, 2021

11. 11
Can we automatically generate these information types?
Color scale according to number of comments falling into a category
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Categories
Pharo
versions
(total
classes)

12. 12
Objects are responsible members of an
object community
Rebecca Wirfs-Brock
Object role stereotypes in 1992 in a Smalltalk Report article

13. 13
Objects are responsible members of an
object community
Rebecca Wirfs-Brock
Object role stereotypes in 1992 in a Smalltalk Report article

14. 14
Controller
Coordinator
Structure
Interface
Information holder
Objects are responsible members of an
object community
Rebecca Wirfs-Brock
Object role stereotypes in 1992 in a Smalltalk Report article

15. 15
Controller
Coordinator
Structure
Interface
Information holder
Objects are responsible members of an
object community
Object role stereotypes in 1992 in a Smalltalk Report article
Stereotype-based approach

16. 16
Previous works

17. 17
Previous works

18. 18
Previous works

19. 19
Previous works

20. 20
Methodology Dataset
Can We Automatically Generate Class Comments in
Pharo?
Previous works

21. 21
Methodology
Identify
class stereotype
Identify method
stereotypes
Pharo 8 Extract
method information
Extract
class
information
Fill
template
1 2 3 4 5

22. 22
• Accessor
• Getter
• Mutator
• Setter
• Creational
• Collaborator
• Degnerate
• Controller
Method Stereotypes
1

23. 23
4%
4%
4%
5%
10%
16%
28%
33%
Set
Get
Controller
Creational
Mutator
Degenerate
Collaborator
Accessor
Distribution of Stereotypes
• Accessor
• Getter
• Mutator
• Setter
• Creational
• Collaborator
• Degnerate
• Controller
Method Stereotypes
1

24. 24
• Entity
• Minimal Entity
• Data Provider
• Commander
• Boundary
• Factory
• Empty
• Small
• Controller
• Pure Controller
• Large
• Lazy
• Degenerate
• Data
Class Stereotypes
2
4%
4%
4%
5%
10%
16%
28%
33%
Set
Get
Controller
Creational
Mutator
Degenerate
Collaborator
Accessor
• Accessor
• Getter
• Mutator
• Setter
• Creational
• Collaborator
• Degnerate
• Controller
Method Stereotypes
1
Distribution of Stereotypes

25. 25
0%
1%
2%
2%
2%
2%
2%
3%
5%
6%
7%
9%
23%
42%
PureController
Lazy
Controller
Data
Entity
Factory
MinimalEntity
Empty
Commander
Small
Large
Degenerate
Boundary
DataProvider
4%
4%
4%
5%
10%
16%
28%
33%
Set
Get
Controller
Creational
Mutator
Degenerate
Collaborator
Accessor
• Entity
• Minimal Entity
• Data Provider
• Commander
• Boundary
• Factory
• Empty
• Small
• Controller
• Pure Controller
• Large
• Lazy
• Degenerate
• Data
Class Stereotypes
2
• Accessor
• Getter
• Mutator
• Setter
• Creational
• Collaborator
• Degnerate
• Controller
Method Stereotypes
1
Distribution of Stereotypes

26. 26
• Entity
• Minimal Entity
• Data Provider
• Commander
• Boundary
• Factory
• Empty
• Small
• Controller
• Pure Controller
• Large
• Lazy
• Degenerate
• Data
Class Stereotypes
2
• Accessor
• Getter
• Mutator
• Setter
• Creational
• Collaborator
• Degnerate
• Controller
Method Stereotypes
1

27. 27
Small
Controller
Pure Controller
Large
Lazy
Degenerate
Data
otypes
reational
ollaborator
egnerate
ontroller
eotypes

28. 28
• External used methods
• Internally used methods
Method Information
3
• Class name
• Class stereotype description
• Classes used by the class
• Dependent classes
• Relevant keywords
Class Information
4
Small
Controller
Pure Controller
Large
Lazy
Degenerate
Data
otypes
reational
ollaborator
egnerate
ontroller
eotypes

29. 29
• External used methods
• Internally used methods
Method Information
3
• Class name
• Class stereotype description
• Classes used by the class
• Dependent classes
• Relevant keywords
Class Information
4
Small
Controller
Pure Controller
Large
Lazy
Degenerate
Data
otypes
reational
ollaborator
egnerate
ontroller
eotypes

30. 30
• External used methods
• Internally used methods
Method Information
3
• Class name
• Class stereotype description
• Classes used by the class
• Dependent classes
• Relevant keywords
Class Information
4
Small
Controller
Pure Controller
Large
Lazy
Degenerate
Data
otypes
reational
ollaborator
egnerate
ontroller
eotypes

31. 31
24 class comments (auto generated)
3 developers: each comment evaluated by three
42 evaluations: 7 developers completed it
3 metrics: Adequacy, Conciseness, Comprehensibility
Evaluation

32. 32
Evaluation
Adequacy: 44% participants said the comment is missing some important information

33. 33
Conciseness- 54% participants said the comment contains a lot of
unnecessary information
Evaluation
Adequacy: 44% participants said the comment is missing some important information