> if they have setup their projects correctly. Can you be more clear about what "setup their projects correctly" means? If you are referring to usage of --release, you seem to be making a pretty strong argument that this will not be the case.
> We tested Apache Lucene and Apache Solr with Java 21. > We have extensive use of chains of stream() calls with Stream.of() and similar apis > Use of "var" is still seldom I'm sorry, but this doesn't seem to contradict the concern raised by Remi. He, apparently, has codebases that do not compile as a result of the SequencedCollections change. This means either * He is doing something in those codebases which is uncommon and the risk of wider breakage was adequately assessed by the Corpus experiment. * He is doing something that is more common than the Corpus experiment showed and that Corpus is not representative in a meaningful way. That Lucene and Solr are in the clear doesn't seem relevant. There is an implicit filter on the Java community of all the folks who even touch preview builds, who would feel comfortable using a mailing list, and who would feel comfortable offering a dissenting opinion. I don't know what that means in terms of statistical significance of his issues, but it would be insane if there was no effect. On Wed, May 17, 2023 at 3:58 AM Uwe Schindler <uschind...@apache.org> wrote: > Hi Remi, hi all, > I'd like to add some information from open source projects and why I don't > see the problem discussed here is a really serious one. > > Background: We tested Apache Lucene and Apache Solr with Java 21. The > compilation with Gradle went fine. So actually there are no problems with > the new superclasses. We have extensive use of chains of stream() calls > with Stream.of() and similar apis. Use of "var" is still seldom but we use > it now when newly introduced code around streams is added to spare > verbosity. But still we got no problems. But why is this so? > > A good open source project should trigger the compiler with "--release". > Apache Lucene uses Java 17 on main branch and Java 11 on 9.x branch. In > both cases compilation worked due to the use of "--release". If we would > change to Java 21 as compilation target, we may need to adapt our code. > > There are some problems with that: > > - Not all projects use "--release", some projects still use "--source > --target". The problem with that is Maven and Gradle still not making > "--release" a first class citizen. Default configs only use "--source > --target". > - Code still on Java 8 can't use "--release", as the compiler does not > support it. The Lucene 8.x branch still open for bugfixes has a trick: It > detects the compiler and if it is Java 8 it passes "--source 8 --target 8", > while starting with Java 9 compiler it passes "--release 8". On the other > hand code still supporting java 8 is unlikely affected by the problem, as > it cannot use "var". But still chains of Stream.of().foo().bar() may still > be affected. > > What is a more serious source-incompatibility issue that I would always > report to OpenJDK bug tracker: During testing Java 20 we were trapped by a > compiler change that caused a source incompatibility (which was reverted, > see https://bugs.openjdk.org/browse/JDK-8299416). So not even passing > "--release" fixed the issue, because the compiler changed its semantics. > This is in my opinion a breaking issue because it prevents code from > compiling! > > The changes in sequenced collections should not be a too big problem for > the community if they have setup their projects correctly. > > Uwe > > P.S.: To be honest: I tried to pass "--release 21" when compiling Lucene > and it failed, but not for sequenced collections reasons. It was more some > tests calling Runtime#runFinalization(). > > Am 05.05.2023 um 13:14 schrieb fo...@univ-mlv.fr: > > Hi Joe, > in this peculiar case, there are several reasons to be worried compared to > other potential breaking changes that has appeared in the past (see the > message of Tagir for an example). > > Unlike other changes > - this one touch the collection API, and those interfaces/types are widely > used, > - we know that the source compatibility changes occurs mostly if 'var' or > the "new" inference algorithm (the one from Java 8), so this is likely that > most of the issues will be found in Java 11+ source code, > - this changes may also affect all typed languages based on the JVM, not > only Java. Corpus of codes in Groovy, Kotlin and Scala also need to be > checked. In case of Kotlin and Scala, 'var' is the default behavior but > they have their own collections (or type system around collections in case > of Kotlin), so knowing the real impact of this change is hard here. > > The problem of using a corpus experiment is that the corpus may not > represent the current state of the Java ecosystem, or at least the one that > may be impacted. > > The problem with the corpus experiment is also that you need to be aware > that most moden open source projects use "--release" flag, so you have to > patch it away from the build system. > > In my case, on my own repositories (public and private), i had only one > occurrence of the issue in the main source codes because many of those > repositories are not using 'var' or even the stream API but on the corpus > of the unit tests we give to students to check their implementations, > little less than a third of those JUnit classes had source compatibility > issues because those tests are using 'var' and different collections > heavily. > > And the situation is a little worst than that because in between now and > the time people will use Java 21, a lot of codes will be written using Java > 11 and 17 and may found incompatible later. > > A source incompatibility issue is not a big deal, as said in this thread, > most of the time, explicitly fixing the type argument instead of inferring > it make the code compile again. > So the house is not burning, but we should raise awareness of this issue > given that it may have a bigger impact than other source incompatible > changes that occur previously. > > Rémi > > ------------------------------ > > *From: *"joe darcy" <joe.da...@oracle.com> <joe.da...@oracle.com> > *To: *"Ethan McCue" <et...@mccue.dev> <et...@mccue.dev>, "Raffaello > Giulietti" <raffaello.giulie...@oracle.com> > <raffaello.giulie...@oracle.com> > *Cc: *"Remi Forax" <fo...@univ-mlv.fr> <fo...@univ-mlv.fr>, "Stuart > Marks" <stuart.ma...@oracle.com> <stuart.ma...@oracle.com>, > "core-libs-dev" <core-libs-...@openjdk.java.net> > <core-libs-...@openjdk.java.net> > *Sent: *Friday, May 5, 2023 4:38:16 AM > *Subject: *Re: The introduction of Sequenced collections is not a source > compatible change > > A few comments on the general compatibility policy for the JDK. > Compatibility is looked after by the Compatibility and Specification Review > (CSR) process ( Compatibility & Specification Review). Summarizing the > approach, > > The general compatibility policy for exported APIs implemented in the JDK > is: > > * Don't break binary compatibility (as defined in the Java Language > Specification) without sufficient cause. > * Avoid introducing source incompatibilities. > * Manage behavioral compatibility changes. > > https://wiki.openjdk.org/display/csr/Main > > None of binary, source, and behavioral compatibly are absolutes and > judgement is used to assess the cost/benefits of changes. For example, > strict source compatibility would preclude, say, introducing new public > types in the java.lang package since the implicit import of types in > java.lang could conflict with a same-named type *-imported from another > package. > > When a proposed change is estimated to be sufficiently disruptive, we > conduct a corpus experiment to evaluate the impact on the change on many > public Java libraries. Back in Project Coin in JDK 7, that basic approach > was used to help quantify various language design choices and the > infrastructure to run such experiments has been built-out in the subsequent > releases. > > HTH, > > -Joe > CSR Group Lead > On 5/4/2023 6:32 AM, Ethan McCue wrote: > > I guess this a good time to ask, ignoring the benefit part of a cost > benefit analysis, what mechanisms do we have to measure the number of > codebases relying on type inference this will break? > > Iirc Adoptium built/ran the unit tests of a bunch of public repos, but > it's also a bit shocking if the jtreg suite had nothing for this. > > On Thu, May 4, 2023, 9:27 AM Raffaello Giulietti < > raffaello.giulie...@oracle.com> wrote: > >> Without changing the semantics at all, you could also write >> >> final List<Collection<String>> list = >> Stream.<Collection<String>>of(nestedDequeue, nestedList).toList(); >> >> to "help" type inference. >> >> >> >> >> On 2023-05-03 15:12, fo...@univ-mlv.fr wrote: >> > Another example sent to me by a fellow French guy, >> > >> > final Deque<String> nestedDequeue = new ArrayDeque<>(); >> > nestedDequeue.addFirst("C"); >> > nestedDequeue.addFirst("B"); >> > nestedDequeue.addFirst("A"); >> > >> > final List<String> nestedList = new ArrayList<>(); >> > nestedList.add("D"); >> > nestedList.add("E"); >> > nestedList.add("F"); >> > >> > final List<Collection<String>> list = Stream.of(nestedDequeue, >> nestedList).toList(); >> > >> > This one is cool because no 'var' is involved and using >> collect(Collectors.toList()) instead of toList() solves the inference >> problem. >> > >> > Rémi >> > >> > ----- Original Message ----- >> >> From: "Stuart Marks" <stuart.ma...@oracle.com> >> >> To: "Remi Forax" <fo...@univ-mlv.fr> >> >> Cc: "core-libs-dev" <core-libs-...@openjdk.java.net> >> >> Sent: Tuesday, May 2, 2023 2:44:28 AM >> >> Subject: Re: The introduction of Sequenced collections is not a source >> compatible change >> > >> >> Hi Rémi, >> >> >> >> Thanks for trying out the latest build! >> >> >> >> I'll make sure this gets mentioned in the release note for Sequenced >> >> Collections. >> >> We'll also raise this issue when we talk about this feature in the >> Quality >> >> Outreach >> >> program. >> >> >> >> s'marks >> >> >> >> On 4/29/23 3:46 AM, Remi Forax wrote: >> >>> I've several repositories that now fails to compile with the latest >> jdk21, which >> >>> introduces sequence collections. >> >>> >> >>> The introduction of a common supertype to existing collections is >> *not* a source >> >>> compatible change because of type inference. >> >>> >> >>> Here is a simplified example: >> >>> >> >>> public static void m(List<Supplier<? extends Map<String, >> String>>> factories) { >> >>> } >> >>> >> >>> public static void main(String[] args) { >> >>> Supplier<LinkedHashMap<String,String>> supplier1 = >> LinkedHashMap::new; >> >>> Supplier<SortedMap<String,String>> supplier2 = TreeMap::new; >> >>> var factories = List.of(supplier1, supplier2); >> >>> m(factories); >> >>> } >> >>> >> >>> >> >>> This example compiles fine with Java 20 but report an error with Java >> 21: >> >>> SequencedCollectionBug.java:28: error: method m in class >> SequencedCollectionBug >> >>> cannot be applied to given types; >> >>> m(factories); >> >>> ^ >> >>> required: List<Supplier<? extends Map<String,String>>> >> >>> found: List<Supplier<? extends SequencedMap<String,String>>> >> >>> reason: argument mismatch; List<Supplier<? extends >> SequencedMap<String,String>>> >> >>> cannot be converted to List<Supplier<? extends >> Map<String,String>>> >> >>> >> >>> >> >>> >> >>> Apart from the example above, most of the failures I see are in the >> unit tests >> >>> provided to the students, because we are using a lot of 'var' in them >> so they >> >>> work whatever the name of the types chosen by the students. >> >>> >> >>> Discussing with a colleague, we also believe that this bug is not >> limited to >> >>> Java, existing Kotlin codes will also fail to compile due to this bug. >> >>> >> >>> Regards, >> >>> Rémi >> > > -- > Uwe schindleruschind...@apache.org > ASF Member, Member of PMC and Committer of Apache Lucene and Apache Solr > Bremen, Germanyhttps://lucene.apache.org/https://solr.apache.org/ > >
