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

[Jonathan Gibbons]

+1 on an RFE to get a numeric version from a source version, either now 
or in a follow-up RFE ... and potentially the reverse as well, to get a 
SourceVersion from a numeric argument.  Both would help with analyzing 
and creating command-line arguments, without excessive string-bashing or 
side-maps.

-- Jon


On 03/22/2019 11:14 AM, Liam Miller-Cushon wrote:
> Thanks Joe,
>
> This looks good to me overall, for what it's worth.
>
> Some minor notes:
>
> * I think it might still be helpful to capture some of your 
> explanation from the bug in the javadoc for latestSupported(), to help 
> users understand when the use of that method is appropriate.
>
> * Your explanation of the lower bound might make a good implementation 
> comment to explain the use of RELEASE_9.
>
> * Also, have you considered including the numeric feature version in 
> the enum constants in SourceVersion? It might avoid some of the 
> hard-coded version numbers in getLatestSupported. I'm imagining 
> something along the lines of:
> http://cr.openjdk.java.net/~cushon/8221264/webrev.00/src/java.compiler/share/classes/javax/lang/model/SourceVersion.java.sdiff.html 
> <http://cr.openjdk.java.net/%7Ecushon/8221264/webrev.00/src/java.compiler/share/classes/javax/lang/model/SourceVersion.java.sdiff.html>
>
> On Fri, Mar 22, 2019 at 10:34 AM Joe Darcy <joe.darcy at oracle.com 
> <mailto:joe.darcy at oracle.com>> wrote:
>
>     Hello,
>
>     Responding to an rfe filed by Liam, please review a refactoring of
>     the
>     SourceVersion.latestSupported method:
>
>          JDK-8221264: Refactor SourceVersion#latestSupported
>     http://cr.openjdk.java.net/~darcy/8221264.0/
>     <http://cr.openjdk.java.net/%7Edarcy/8221264.0/>
>
>     Patch below.
>
>     With this version, when it comes time to rev a release for 14, the
>     line
>
>     +            return valueOf("RELEASE_" + Math.min(13, intVersion));
>
>     will need to be changed to
>
>     +            return valueOf("RELEASE_" + Math.min(14, intVersion));
>
>     In general the JSR 269 packages, javax.lang.model and
>     javax.annotation.processing, are constrained by bootstrapping
>     issue to
>     be runnable on JDK (N-1); in other words, they cannot only run on
>     JDK N.
>     It may or may not be possible to compile the code to run on JDK
>     (N-2) or
>     earlier. For example, since JDK 9, the JSR 269 API has used default
>     methods so the API certainly cannot be compiled and run earlier
>     than JDK 8.
>
>     The Runtime.Version type was introduced in JDK 9; its feature()
>     method
>     in 10.
>
>     The proposed implementation is simple, even if it is not completely
>     accurate in a current lower bound for running the API; I don't think
>     being more accurate on this lower bound is necessary.
>
>     Thanks,
>
>     -Joe
>
>     ---
>     old/src/java.compiler/share/classes/javax/lang/model/SourceVersion.java
>
>     2019-03-22 10:09:33.870668998 -0700
>     +++
>     new/src/java.compiler/share/classes/javax/lang/model/SourceVersion.java
>
>     2019-03-22 10:09:33.526668998 -0700
>     @@ -209,30 +209,13 @@
>           private static final SourceVersion latestSupported =
>     getLatestSupported();
>
>           private static SourceVersion getLatestSupported() {
>     -        try {
>     -            String specVersion =
>     System.getProperty("java.specification.version");
>     +        int intVersion = Runtime.version().feature();
>
>     -            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;
>     +        if (intVersion >= 10) {
>     +            return valueOf("RELEASE_" + Math.min(13, intVersion));
>     +        } else {
>     +            return RELEASE_9;
>     +        }
>           }
>
>           /**
>

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