JDK 15 RFR of JDK-8240130: Improve and update discussion of visitor evolution warnings

Joe Darcy joe.darcy at oracle.com
Fri Mar 13 19:13:52 UTC 2020 

On 3/13/2020 11:38 AM, Jonathan Gibbons wrote:
>
> Generally OK, although you may have removed a bit too much text (i.e. 
> the @param tags) in
> src/java.compiler/share/classes/javax/lang/model/util/AbstractElementVisitor8.java
>
Thanks for catching this; will fix before pushing.


> I note inconsistent use of a blank line after `@apiNote`. I'm not sure 
> if that is intentional.
>
Before pushing, I'll re-flow the paragraphs and delete and a spacer line 
between @apiNote and the subsequent text.

-Joe

> -- Jon
>
>
> On 03/13/2020 11:16 AM, Joe Darcy wrote:
>>
>> Hello,
>>
>> Following an off-list suggestion from Jon, I've re-worked the change 
>> to remove most of the WARNING paragraphs and replace them with @see 
>> links:
>>
>> http://cr.openjdk.java.net/~darcy/8240130.2
>>
>> Each root visitor/scanner has a slightly different wording; the 
>> element kind visitor is not strictly correct without a specialized 
>> wording. Therefore, visitors other than the AbstractFooVisitor6 have 
>> warning paragraphs.
>>
>> Thanks Jon for the helpful suggestion.
>>
>> -Joe
>>
>> On 3/10/2020 10:09 PM, Joe Darcy wrote:
>>>
>>> Hello,
>>>
>>> Updated and expanded version of the webrev:
>>>
>>> http://cr.openjdk.java.net/~darcy/8240130.1
>>>
>>> A few notes on reviewing:
>>>
>>>     * The delta for each FooVisitor$N utility visitor family should 
>>> be the same. I confirmed this visually by aligning up the udiffs of 
>>> each family and switching between tabs.
>>>
>>>     * To highlight the text differences, I did *not* reflow the 
>>> paragraphs in this webrev. I'll do that before a push.
>>>
>>>     * Some visitors had a tip
>>>
>>>> Note that annotating methods in concrete
>>>> subclasses with {@link java.lang.Override @Override} will help
>>>>  ensure that methods are overridden as intended.
>>>
>>>     While this may have been useful back in JDK 6, I don't think it 
>>> is needed in JDK 15 and I'm proposing to remove these notes.
>>>
>>>     * The wording in TypeKindVisitor$N was updated to explicitly 
>>> mention the possibility of new enum values being added, aligning 
>>> with the wording already in use in ElementKindVisitor$N.
>>>
>>> Thanks,
>>>
>>> -Joe
>>>
>>>
>>> On 3/5/2020 12:18 PM, Jonathan Gibbons wrote:
>>>>
>>>> Looks good to me.
>>>>
>>>> Consider using a ':' instead of ',' on this line in the first file:
>>>>
>>>> 66 * visitUnknown}, behavior that will be overridden in concrete
>>>> -- Jon
>>>>
>>>> On 2/26/20 10:00 PM, Joe Darcy wrote:
>>>>> Hello,
>>>>>
>>>>> Please review the documentation changes for
>>>>>
>>>>>     JDK-8240130: Improve and update discussion of visitor 
>>>>> evolution warnings
>>>>> http://cr.openjdk.java.net/~darcy/8240130.0/
>>>>>
>>>>> Patch below. Some discussion of and rationale for the changes, the 
>>>>> original javax.lang.model visitor interfaces and concrete visitor 
>>>>> types had various warning about the unusual compatibility policies 
>>>>> those types would use. Unlike other post-Java SE 6 era types, it 
>>>>> was anticipated methods would be added to interfaces. Prior to 
>>>>> default methods in JDK 8, such additions were a highly unusual 
>>>>> occurrence for public types in the JDK. After default methods were 
>>>>> used commonly in jDK 8, such additions are of less concern. The 
>>>>> risk of a true source compatibility is also low for a new 
>>>>> "visitFoo" method since it will have a parameter of type Foo, 
>>>>> which is new to the release, and thus not have an overloading 
>>>>> conflict with a method in an existing visitor outside of the JDK.
>>>>>
>>>>> The warnings are thus toned down and adjusted to note that the 
>>>>> envisioned additions have already occurred for prior language 
>>>>> additions. For example, the current policy is only to deprecate 
>>>>> the constructors of obsolete visitor classes rather than the whole 
>>>>> class. The "directly or indirectly call" visitUnknown is to 
>>>>> accurately describe, but not limit to, the current policy of the 
>>>>> visitFoo methods in affected concrete visitors calling the 
>>>>> visitFoo default method on the *interface*, which in turn calls 
>>>>> visitUnknown.
>>>>>
>>>>> The warning text is pulled into an apiNote to avoid getting 
>>>>> inherit-doc-ed for any subclasses. Once the shape of the changes 
>>>>> for the interface and visitor classes are agree to, I'll 
>>>>> replicated the changes for the other types.
>>>>>
>>>>> Thanks,
>>>>>
>>>>> -Joe
>>>>>
>>>>> --- 
>>>>> old/src/java.compiler/share/classes/javax/lang/model/element/ElementVisitor.java 
>>>>> 2020-02-26 13:13:00.848880601 -0800
>>>>> +++ 
>>>>> new/src/java.compiler/share/classes/javax/lang/model/element/ElementVisitor.java 
>>>>> 2020-02-26 13:13:00.512880601 -0800
>>>>> @@ -40,10 +40,17 @@
>>>>>   * is {@code null}; see documentation of the implementing class for
>>>>>   * details.
>>>>>   *
>>>>> - * <p> <b>WARNING:</b> It is possible that methods will be added to
>>>>> + * @apiNote
>>>>> + *
>>>>> + * WARNING: It is possible that methods will be added to
>>>>>   * this interface to accommodate new, currently unknown, language
>>>>>   * structures added to future versions of the Java™ 
>>>>> programming
>>>>> - * language.  Therefore, visitor classes directly implementing this
>>>>> + * language.
>>>>> + *
>>>>> + * Such additions have already occurred to support language features
>>>>> + * added after this API was introduced.
>>>>> + *
>>>>> + * Visitor classes directly implementing this
>>>>>   * interface may be source incompatible with future versions of the
>>>>>   * platform.  To avoid this source incompatibility, visitor
>>>>>   * implementations are encouraged to instead extend the appropriate
>>>>> @@ -52,21 +59,15 @@
>>>>>   * parameters, return type, etc. rather than one of the abstract
>>>>>   * classes.
>>>>>   *
>>>>> - * <p>Note that methods to accommodate new language constructs could
>>>>> - * be added in a source <em>compatible</em> way if they were 
>>>>> added as
>>>>> - * <em>default methods</em>.  However, default methods are only
>>>>> - * available on Java SE 8 and higher releases and the {@code
>>>>> - * javax.lang.model.*} packages bundled in Java SE 8 were 
>>>>> required to
>>>>> - * also be runnable on Java SE 7.  Therefore, default methods
>>>>> - * were <em>not</em> used when extending {@code javax.lang.model.*}
>>>>> - * to cover Java SE 8 language features.  However, default methods
>>>>> - * are used in subsequent revisions of the {@code 
>>>>> javax.lang.model.*}
>>>>> - * packages that are only required to run on Java SE 8 and higher
>>>>> - * platform versions.
>>>>> - *
>>>>> - * @apiNote
>>>>> + * <p>Methods to accommodate new language constructs are expected to
>>>>> + * be added as default methods to provide strong source 
>>>>> compatibility,
>>>>> + * as done for {@link visitModule visitModule}. The 
>>>>> implementations of
>>>>> + * the default methods will in turn call {@link visitUnknown
>>>>> + * visitUnknown}, behavior that will be overridden in concrete
>>>>> + * visitors supporting the source version with the new language
>>>>> + * construct.
>>>>>   *
>>>>> - * There are several families of classes implementing this visitor
>>>>> + * <p>There are several families of classes implementing this 
>>>>> visitor
>>>>>   * interface in the {@linkplain javax.lang.model.util util
>>>>>   * package}. The families follow a naming pattern along the lines of
>>>>>   * {@code FooVisitor}<i>N</i> where <i>N</i> indicates the
>>>>> --- 
>>>>> old/src/java.compiler/share/classes/javax/lang/model/util/AbstractElementVisitor6.java 
>>>>> 2020-02-26 13:13:01.560880601 -0800
>>>>> +++ 
>>>>> new/src/java.compiler/share/classes/javax/lang/model/util/AbstractElementVisitor6.java 
>>>>> 2020-02-26 13:13:01.196880601 -0800
>>>>> @@ -36,7 +36,9 @@
>>>>>   * appropriate for the {@link SourceVersion#RELEASE_6 RELEASE_6}
>>>>>   * source version.
>>>>>   *
>>>>> - * <p> <b>WARNING:</b> The {@code ElementVisitor} interface
>>>>> + * @apiNote
>>>>> + *
>>>>> + * <strong>WARNING:</strong> The {@code ElementVisitor} interface
>>>>>   * implemented by this class may have methods added to it in the
>>>>>   * future to accommodate new, currently unknown, language structures
>>>>>   * added to future versions of the Java™ programming language.
>>>>> @@ -46,12 +48,12 @@
>>>>>   * methods with names beginning with {@code "visit"}.
>>>>>   *
>>>>>   * <p>When such a new visit method is added, the default
>>>>> - * implementation in this class will be to call the {@link
>>>>> + * implementation in this class will be to directly or indirectly 
>>>>> call the {@link
>>>>>   * #visitUnknown visitUnknown} method.  A new abstract element 
>>>>> visitor
>>>>>   * class will also be introduced to correspond to the new language
>>>>>   * level; this visitor will have different default behavior for the
>>>>> - * visit method in question.  When the new visitor is introduced, 
>>>>> all
>>>>> - * or portions of this visitor may be deprecated.
>>>>> + * visit method in question.  When a new visitor is introduced,
>>>>> + * portions of this visitor class may be deprecated, including 
>>>>> its constructors.
>>>>>   *
>>>>>   * @param <R> the return type of this visitor's methods. Use {@link
>>>>>   *            Void} for visitors that do not need to return results.
>>>>>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://mail.openjdk.java.net/pipermail/compiler-dev/attachments/20200313/05142c78/attachment-0001.htm>

More information about the compiler-dev mailing list