Wow, so this stuff is literally "hot off the press"! Is this likely to end up in the 3.x series, or need to upgrade to 4? Also, once it goes in, can this please be documented somewhere more "official" than a release notes thingy?
-----Original Message----- From: Tamás Cservenák <ta...@cservenak.net> Sent: Thursday, July 27, 2023 11:29 AM To: Maven Users List <users@maven.apache.org> Subject: Re: maven class path order documentation CAUTION: This email originated from outside our organisation - ta...@cservenak.net Do not click on links, open attachments, or respond unless you recognize the sender and can validate the content is safe. And here it is: https://clicktime.symantec.com/15sipz7F5STrvRGrevHBY?h=7Y8hfhGCp9uBBufC8Pdra11MjKQK1pB9sZxKj0WyVT4=&u=https://github.com/apache/maven/pull/1212 To have this tested, first build this https://clicktime.symantec.com/15sik9uxcpnGWUSw7Mt2v?h=Ykgfx9FlWtp9Mzx3hItBj6j3zdtVOq7AohrAHo-SEhg=&u=https://github.com/apache/maven-resolver/pull/322 then this: https://clicktime.symantec.com/15sipz7F5STrvRGrevHBY?h=7Y8hfhGCp9uBBufC8Pdra11MjKQK1pB9sZxKj0WyVT4=&u=https://github.com/apache/maven/pull/1212 And you will end up with maven: - that fully delegates to resolver classpath ordering (removed all places where they are "sorted", it is done by resolver) - resolver supports "preOrder, "postOrder" and "levelOrder" transformation Examples: preOrder https://clicktime.symantec.com/15siaVXPhbR5gao62F5jg?h=ZNj2Gfw4KUWOqAboOy7hrW4_dA-8ANFsatojmBQ23HU=&u=https://gist.github.com/cstamas/d1cb11d96938cdb9e6da2b46eec449b6 levelOrder https://clicktime.symantec.com/15siQq8pnN3trh9Ew8HSS?h=SFbeFNH1ZOnGqJUbSsU15ER7BNDe9eZuFYruemWExQo=&u=https://gist.github.com/cstamas/6498cfb31afe74ded1471c02d982eee6 Observe how collected trees are TOTALLY SAME, but classpath order differs. Thanks T On Thu, Jul 27, 2023 at 4:51 PM Tamás Cservenák <ta...@cservenak.net> wrote: > What a coincidence... > > I just started looking at an old issue (was looking at some edge > cases) where even reproducer exists and tackles similar topic: > https://clicktime.symantec.com/15siupJXY49TLN6nCUgLA?h=7vkUPM03eakDwHh > dabKdvr3cDonDm1gylwtF58tHzag=&u=https://issues.apache.org/jira/browse/ > MNG-6357 > > Then I went to maven sources and resolver sources to ensure what is > happening. > > Sadly, maven is not quite consistent in this matter, but is at least > aligned: > - at some places it uses PreorderNodeListGenerator to generate > classpath (and/or ordered artifacts) > - at some other places it relies on resolver ordering (that ALSO > implicitly uses preorder) > > The class in question: > > https://clicktime.symantec.com/15sifKigAD6g6Xd1ZoUtJ?h=SEFwjM88CuRbMjD > -_g1kUUwvb0y9AuM49l0EoicAJ_o=&u=https://github.com/apache/maven-resolv > er/blob/maven-resolver-1.9.14/maven-resolver-util/src/main/java/org/ec > lipse/aether/util/graph/visitor/PreorderNodeListGenerator.java > > The example output: > https://clicktime.symantec.com/15siVfL7EyjVGdyAUggb4?h=eKPHFWmgDwUy2Jd > 9zqj7FZMg0YLR8cEQ_HTJ5N88EVk=&u=https://gist.github.com/cstamas/ca113c > 1d6697540a4cf55c3098b9a550 > > As you can see in example, the classpath is basically ordered as > "reading the tree", this causes that for example maven-dependency-tree > (2nd level > dependency) comes BEFORE enforcer-api (1sd level) dependency. > > So, I myself find this wrong as well, but at least the statement you > found "introduced deterministic ordering of dependencies on the > classpath" still stands today: is PreOrder. > > Then occurred to me that this is easily customisable, so I went for > start to create this: > https://clicktime.symantec.com/15sik9uxcpnGWUSw7Mt2v?h=Ykgfx9FlWtp9Mzx > 3hItBj6j3zdtVOq7AohrAHo-SEhg=&u=https://github.com/apache/maven-resolv > er/pull/322 > > But this is only half of the story, as the Maven part is missing, > especially where Maven sorts itself... > > All in all, an interesting coincidence.... > > As for your other question: what resolver does is > - builds a "dirty tree" (graph more precisely, it may have loops), we > have two algorithms for this: original depth-first (DF) and new > breadth-first > (BF) > - applies conflict resolution (this is where "winners" are set, ie. > "closest wins" in case of duplicates) > - resulted "clean tree" is transformed into list of (resolved) > artifacts, possibly into classpath as well > - OR the resolved graph is with class like (but > consistently) PreorderNodeListGenerator used to create classpath -- so > PreOrder is applied always > > Thanks > T > > > On Thu, Jul 27, 2023 at 3:51 PM > <mark.yagnatin...@barclays.com.invalid> > wrote: > >> Re-sending... didn't go through I think: >> >> In the release notes for Maven 2.0.9: >> >> https://clicktime.symantec.com/15siFAkFs8gi2oVPr1V9C?h=CzqA8kBOdhB05Y >> fPbEvxwyofbPnfsaxl96JNiQ24c3U=&u=http://people.apache.org/~jvanzyl/ma >> ven-3.1.1/docs/2.0.9/release-notes.html >> It says: "introduced deterministic ordering of dependencies on the >> classpath. In the past, natural set ordering was used and this lead >> to odd results. The ordering is now preserved from your pom, with >> dependencies added by inheritance added last" >> Is this info still current? Is it documented anywhere aside from >> this release note? If not, perhaps it should be? And more details >> would be nice too. For instance: >> >> * Suppose my module M has parent P and grandparent G. Also, M >> depends on A and B, in that order. Further, suppose A depends on X, >> which in turn depends on Y. Meanwhile, B depends on Z. >> >> Based on the sentence above, both of these are plausible orders: >> >> a. M, A, B, X, Z, Y, P, G >> >> b. M, A, X, Y, B, Z, P, G >> >> c. Maybe others too? >> >> * How does this relate to the dependency "mediation" algorithm >> maven uses when there are conflicting versions of a dependency requested? >> >> As far as I understand, that uses a breadth-first search, where the >> parent pom comes FIRST rather than last. >> >> Does that mean that mediation algorithm is basically unrelated to >> class path algorithm, or do they still have some things in common? >> >> E.g., ordering (a) above is also a breadth-first search, whereas (b) >> is depth-first. >> Any words of wisdom would be nice. >> >> Thanks, >> Mark. >> >> This message is for information purposes only. It is not a >> recommendation, advice, offer or solicitation to buy or sell a >> product or service, nor an official confirmation of any transaction. >> It is directed at persons who are professionals and is intended for >> the recipient(s) only. It is not directed at retail customers. 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