Blessed modifier order does not include sealed/non-sealed

Wed Jan 3 01:49:39 UTC 2024

Hello,

Some time back, the java.lang.reflect package level docs had a brief 
discussion added concerning what exactly core reflection is modeling. 
[1]. tl;dr -- mostly a class file level view. As such, a contingent 
property of the design of JEP 409 is that sealed/non-sealed happens to 
_not_ to expressed JVM-level access flags/modifiers. However, it would 
be reasonable IMO for Class.toGenericString(), but not Class.toString(), 
to be updated to expose some sealing-related information. I've filed 
JDK-8322878: "Including sealing information Class.toGenericString()."

-Joe

[1] Added under     JDK-8262807: "Note assumptions of core reflection 
modeling and parameter handling" in JDK 17:

> Java programming language and JVM modeling in core reflection
>
> The components of core reflection, which include types in this package 
> as well as Class, Package, and Module, fundamentally present a JVM 
> model of the entities in question rather than a Java programming 
> language model. A Java compiler, such as javac, translates Java source 
> code into executable output that can be run on a JVM, primarily class 
> files. Compilers for source languages other than Java can and do 
> target the JVM as well.
>
> The translation process, including from Java language sources, to 
> executable output for the JVM is not a one-to-one mapping. Structures 
> present in the source language may have no representation in the 
> output and structures not present in the source language may be 
> present in the output. The latter are called synthetic structures. 
> Synthetic structures can include methods, fields, parameters, classes 
> and interfaces. One particular kind of synthetic method is a bridge 
> method. It is possible a synthetic structure may not be marked as 
> such. In particular, not all class file versions support marking a 
> parameter as synthetic. A source language compiler generally has 
> multiple ways to translate a source program into a class file 
> representation. The translation may also depend on the version of the 
> class file format being targeted as different class file versions have 
> different capabilities and features. In some cases the modifiers 
> present in the class file representation may differ from the modifiers 
> on the originating element in the source language, including final on 
> a parameter and protected, private, and static on classes and interfaces.
>
> Besides differences in structural representation between the source 
> language and the JVM representation, core reflection also exposes 
> runtime specific information. For example, the class loaders and 
> protection domains of a Class are runtime concepts without a direct 
> analogue in source code.

https://download.java.net/java/early_access/jdk23/docs/api/java.base/java/lang/reflect/package-summary.html

On 1/2/2024 8:56 AM, Roger Riggs wrote:
> Hi Pavel,
>
> It better to look to javax.lang.model.element.Modifier 
> <https://docs.oracle.com/en/java/javase/21/docs/api/java.compiler/javax/lang/model/element/Modifier.html> 
> for the language view of the class.
>
> java.lang.reflect.Modifier covers the modifier flags as represented in 
> the class file and defined in the JVMS.
> * The values for the constants * representing the modifiers are taken 
> from the tables in sections * {@jvms 4.1}, {@jvms 4.4}, {@jvms 4.5}, 
> and {@jvms 4.7} of * <cite>The Java Virtual Machine Specification</cite>.
> Sealing is represented in the class file as a non-empty list of 
> permitted classes. Hence the method of java.lang.Class.
>
> Since java.lang.Modifier.toString is based on the flag bits from the 
> class file, "sealed" would not appear in any string it generates.
>
>
> It might be possible to inject a comment in the toString method 
> similar to the comment about interface not being a true modifier and 
> including a reference to the javax.lang.model.element.Modifier enum.
>
> Roger
>
>
> On 1/2/24 11:31 AM, Pavel Rappo wrote:
>> Hi Roger,
>>
>> Happy New Year to you too!
>>
>> Although it's a _somewhat_ separate issue, I found that the shell script refers to java.lang.reflect.Modifier#toString which does NOT mention either `sealed` or `non-sealed`. More precisely, the script refers to the JDK 8 version of that method, but [the method](https://docs.oracle.com/en/java/javase/21/docs/api/java.base/java/lang/reflect/Modifier.html#toString(int))  hasn't changed since 2009 and states that:
>>
>>      ...The modifier names are returned in an order consistent with the suggested modifier orderings given in sections 8.1.1, 8.3.1, 8.4.3, 8.8.3, and 9.1.1 of The Java Language Specification. The full modifier ordering used by this method is:
>>
>>      public protected private abstract static final transient volatile synchronized native strictfp interface
>>
>> It does not seem like `sealed` and `non-sealed` are even modelled by java.lang.reflect.Modifier, although `sealed` is modelled by `java.lang.Class#isSealed`. It cannot be overlook, can it?
>>
>>> On 2 Jan 2024, at 14:38, Roger Riggs<roger.riggs at oracle.com>  wrote:
>>>
>>> Hi Pavel,
>>>
>>> yes, a PR would be next.
>>>
>>> Happy New Year, Roger
>>>
>>> On 1/2/24 7:08 AM, Pavel Rappo wrote:
>>>> I assume the order for `sealed` and `non-sealed` has effectively been decided by JLS:https://docs.oracle.com/javase/specs/jls/se21/html/jls-8.html#jls-8.1.1
>>>>
>>>>      8.1.1. Class Modifiers
>>>>      ...
>>>>           ClassModifier:
>>>>      (one of)
>>>>      Annotation public protected private
>>>>      abstract static final sealed non-sealed strictfp
>>>>           ...
>>>>
>>>>      If two or more (distinct) class modifiers appear in a class declaration, then it is customary, though not required, that they appear in the order consistent with that shown above in the production for ClassModifier.
>>>>
>>>>
>>>> Shall I just create a PR?
>>>>
>>>>> On 2 Jan 2024, at 11:56, Pavel Rappo<pavel.rappo at oracle.com>  wrote:
>>>>>
>>>>> I couldn't find any prior discussions on this matter.
>>>>>
>>>>> I noticed that bin/blessed-modifier-order.sh has not been updated for the [recently introduced](https://openjdk.org/jeps/409) `sealed` and `non-sealed` keywords. I also note that we already have cases in OpenJDK where those keywords are ordered differently. If we have a consensus on how to extend the "blessed order" onto those new keywords, I can create a PR to update the script.
>>>>>
>>>>> -Pavel
>>>>>
>
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