JDK 13 RFR of JDK-8221264: Refactor SourceVersion#latestSupported

[Liam Miller-Cushon]

+1, thanks!

On Mon, Mar 25, 2019 at 4:34 PM Jonathan Gibbons <
jonathan.gibbons at oracle.com> wrote:

> Looks good to me.
>
> -- Jon
>
>
> On 03/25/2019 09:41 AM, Joe Darcy wrote:
> > Hello,
> >
> > Hopefully the final iteration of this patch; updated materials:
> >
> >     8221264 Refactor and update SourceVersion.latestSupported
> >     http://cr.openjdk.java.net/~darcy/8221264.2/
> >     NEW! CSR https://bugs.openjdk.java.net/browse/JDK-8221415
> >
> > I added a comment citing JEP 322: "Time-Based Release Versioning" to
> > justify the new implementation.
> >
> > A CSR is needed because of the update to the minimum version returned,
> > just an @apiNote would not necessarily need a CSR as the changes would
> > be informative rather than normative.
> >
> > The particular implementation below would only work on JDK 10 and
> > higher as it uses a method added in JDK 10. However, the lower-bound
> > of latest supported is raised to JDK *9* rather than JDK 10 since an
> > independent implementation of the API could be written to run and
> > compile against 9.
> >
> > A few additional comments. The most common way of using the
> > javax.lang.model API is expected to be the version bundled in the JDK.
> > There is one particular other use case that has always intended to be
> > supported by JSR 269, namely running the API from JDK N on JDK (N-1)
> > assuming the user had their own compilation of the API. If other
> > mix-and-match use cases work that is fine - and the new implementation
> > should accurately support a larger number of reasonable combinations -
> > but it is a non-goal to impose any additional engineering constraints
> > on the evolution of the API to maximize the range of JDKs it can be
> > run on.
> >
> > Patch below.
> >
> > Thanks,
> >
> > -Joe
> >
> > ---
> > old/src/java.compiler/share/classes/javax/lang/model/SourceVersion.java
> > 2019-03-25 08:53:35.544735632 -0700
> > +++
> > new/src/java.compiler/share/classes/javax/lang/model/SourceVersion.java
> > 2019-03-25 08:53:35.220573632 -0700
> > @@ -58,7 +58,7 @@
> >       *   9: modules, small cleanups to 1.7 and 1.8 changes
> >       *  10: local-variable type inference (var)
> >       *  11: local-variable syntax for lambda parameters
> > -     *  12: TBD
> > +     *  12: no changes (switch expressions in preview)
> >       *  13: TBD
> >       */
> >
> > @@ -208,38 +208,36 @@
> >
> >      private static final SourceVersion latestSupported =
> > getLatestSupported();
> >
> > +    /*
> > +     * The integer to release enum constant implemented by this method
> > +     * assumes the JEP 322: "Time-Based Release Versioning" scheme is
> > +     * in effect. This scheme began in JDK 10. If the JDK versioning
> > +     * scheme is revised, this method may need to be updated
> > +     * accordingly.
> > +     */
> >      private static SourceVersion getLatestSupported() {
> > -        try {
> > -            String specVersion =
> > System.getProperty("java.specification.version");
> > -
> > -            switch (specVersion) {
> > -                case "13":
> > -                    return RELEASE_13;
> > -                case "12":
> > -                    return RELEASE_12;
> > -                case "11":
> > -                    return RELEASE_11;
> > -                case "10":
> > -                    return RELEASE_10;
> > -                case "9":
> > -                    return RELEASE_9;
> > -                case "1.8":
> > -                    return RELEASE_8;
> > -                case "1.7":
> > -                    return RELEASE_7;
> > -                case "1.6":
> > -                    return RELEASE_6;
> > -            }
> > -        } catch (SecurityException se) {}
> > -
> > -        return RELEASE_5;
> > +        int intVersion = Runtime.version().feature();
> > +        return (intVersion >= 11) ?
> > +            valueOf("RELEASE_" + Math.min(13, intVersion)):
> > +            RELEASE_10;
> >      }
> >
> >      /**
> >       * Returns the latest source version fully supported by the
> > -     * current execution environment.  {@code RELEASE_5} or later must
> > +     * current execution environment.  {@code RELEASE_9} or later must
> >       * be returned.
> >       *
> > +     * @apiNote This method is included alongside {@link latest} to
> > +     * allow situations where the language model API is running on a
> > +     * platform version different than the latest version modeled by
> > +     * the API to be identified. One way that sort of situation can
> > +     * occur is if a IDE or similar tool is using the API to model
> > +     * source version <i>N</i> while running on platform version
> > +     * (<i>N</i> - 1). Running in this configuration is
> > +     * supported by the API. Running an API on platform versions
> > +     * earlier than (<i>N</i> - 1) or later than <i>N</i>
> > +     * may or may not work as an implementation detail.
> > +     *
> >       * @return the latest source version that is fully supported
> >       */
> >      public static SourceVersion latestSupported() {
> >
> >
>
>
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