Add Check Support for Java 17 Sealed Classes: AnnotationOnSameLine

[mahfouz72]

child of #14969

Check documentation : https://checkstyle.org/checks/annotation/annotationonsameline.html#AnnotationOnSameLine

---

PS D:\CS\test> javac src/Test.java
PS D:\CS\test> cat config.xml
<?xml version="1.0"?>
<!DOCTYPE module PUBLIC
"-//Puppy Crawl//DTD Check Configuration 1.3//EN"
"http://www.puppycrawl.com/dtds/configuration_1_3.dtd">
<module name="Checker">
<property name="charset" value="UTF-8"/>
<module name="TreeWalker">
<module name="AnnotationOnSameLine">
<property name="tokens" value="INTERFACE_DEF, CLASS_DEF,IMPLEMENTS_CLAUSE"/>
</module>
</module>
</module>
PS D:\CS\test> cat src/Test.java
import java.lang.annotation.Target;

import static java.lang.annotation.ElementType.*;
import static java.lang.annotation.ElementType.TYPE_USE;
class Test{}

sealed @Ann // violation
@Ann2 interface A permits B {}

final @Ann2 // violation
class B implements @Ann // violation
A {}

@Ann // violation
sealed
@Ann2 // violation
class C permits D {}

@Ann sealed
@Ann2 // violation
class E permits F {}


final class D extends C {}
final class F extends E {}

 @Target({TYPE_USE}) @interface Ann {}
@Target({TYPE_USE}) @interface Ann2 {}

PS D:\CS\test> java -jar checkstyle-10.17.0-all.jar -c config.xml src/Test.java
Starting audit...
[ERROR] D:\CS\test\src\Test.java:7:8: Annotation 'Ann' should be on the same line with its target. [AnnotationOnSameLine]
[ERROR] D:\CS\test\src\Test.java:10:7: Annotation 'Ann2' should be on the same line with its target. [AnnotationOnSameLine]
[ERROR] D:\CS\test\src\Test.java:11:20: Annotation 'Ann' should be on the same line with its target. [AnnotationOnSameLine]
[ERROR] D:\CS\test\src\Test.java:14:1: Annotation 'Ann' should be on the same line with its target. [AnnotationOnSameLine]
[ERROR] D:\CS\test\src\Test.java:16:1: Annotation 'Ann2' should be on the same line with its target. [AnnotationOnSameLine]
[ERROR] D:\CS\test\src\Test.java:20:1: Annotation 'Ann2' should be on the same line with its target. [AnnotationOnSameLine]
Audit done.
Checkstyle ends with 6 errors.
PS D:\CS\test>

---

This check working correctly no update is needed.

Note that annotations are not acceptable after permits

PS D:\CS\test> cat src/Test.java
sealed @Ann
@Ann2 interface A permits @Ann // compile time error
B {}

final @Ann2
class B implements @Ann
A {}
....
PS D:\CS\test> javac src/Test.java
src\Test.java:8: error: <identifier> expected
@Ann2 interface A permits @Ann
^
src\Test.java:9: error: class, interface, enum, or record expected
B {}
^
2 errors
PS D:\CS\test>

[rnveach]

@mahfouz72 I am not seeing a compile check that this is valid syntax.

I expect a violation on the annotation after permits

https://docs.oracle.com/javase/specs/jls/se22/html/jls-8.html#jls-ClassPermits
I am not seeing annotations listed as acceptable here in permits.

If this was allowed, why would someone put an annotation on a permits?

[mahfouz72]

sorry this won't compile IntelliJ didn't show an error on this line and I forgot to check Javac. First post is updated

[rnveach]

sealed @Ann // violation
@Ann2 interface A permits B {}

Is it possible for annotations to be before sealed? Show an example with and without violations if you can.

[mahfouz72]

it is possible and I think it works correctly please check first post

[mahfouz72]

@ann sealed
@ann2 // violation
class E permits F {}

I am not sure about this part.

@Ann 's target is class E but we added it before sealed modifier so should this be a violation because the annotation is not on the same line as its target class?

EDIT: I tried to use a public modifier instead of sealed to see how the check deals with this case and the behavior is similar.

@Ann public
@Ann2  // violation
class E {}

[rnveach]

should this be a violation because the annotation is not on the same line as its target class?

https://checkstyle.org/checks/annotation/annotationonsameline.html#Description

Checks that annotations are located on the same line with their targets

If @ann is targeting E then this seems like a yes, this should be a violation.

If the following isn't a violation, then this seems like a bug, but unrelated to sealed classes.

@Ann public
@Ann2 class E {}

@target({CONSTRUCTOR, FIELD, METHOD, PARAMETER, TYPE, TYPE_PARAMETER, TYPE_USE}) @interface Ann {}

You don't use most of these like constructor or field. I would trim these down to the bare minimum and confirm just so we aren't making some type of mistake here on what the "target" is.

[rnveach]

@mahfouz72 I see updates were done, please remember to ping me back so I can remember to come back here and view. So much is going on that I rely on notifications a lot more now.

If the following isn't a violation, then this seems like a bug, but unrelated to sealed classes.

Did you confirm this?

[mahfouz72]

Yes, this bug is unrelated to the sealed class it exists with any modifier. When the Anno is on the same line with the target class modifier but not on the same line with the target class itself

PS D:\CS\test> javac src/Test.java                                               
PS D:\CS\test> cat config.xml                                                    
<?xml version="1.0"?>
<!DOCTYPE module PUBLIC
          "-//Checkstyle//DTD Checkstyle Configuration 1.3//EN"
          "https://checkstyle.org/dtds/configuration_1_3.dtd">

<module name="Checker">
  <module name="TreeWalker">
    <module name="AnnotationOnSameLine"/>
  </module>
</module>
PS D:\CS\test> cat src/Test.java                                                 
import java.lang.annotation.Target;

import static java.lang.annotation.ElementType.TYPE_USE;

public  class Test {
@Ann public   // expected
@Ann2 class E {}

@Ann private  // expected
@Ann2 class A {}

@Ann sealed  // expected
@Ann2 class B permits C {}

@Ann final  // expected
@Ann2 class C extends B {}


@Target({TYPE_USE}) @interface Ann {}
@Target({TYPE_USE}) @interface Ann2 {}
}
PS D:\CS\test> java  -jar checkstyle-10.17.0-all.jar -c config.xml  src/Test.java
Starting audit...
Audit done.

@rnveach I guess we should close this and open a new issue with this code because this is not related to sealed directly

[rnveach]

this is not related to sealed directly

I agree. I feel we can just repurpose this existing issue by updating the title and first post. I am not against just creating a new issue.

[mahfouz72]

@rnveach I updated title and first post please approve if you are good

[nrmancuso]

@mahfouz72 please make a new issue as @rnveach suggested

[mahfouz72]

This can be closed no update is needed related to sealed classes. The discoverd (unrelated to sealed classes) bug has been moved to a new issue #15161