1 - yes 2 - yes (Maven tries hard to simplify things for users, but heh) 3 - yes, model ordering matters, most easily checked with `mvn help:effective-pom`, so to say if depency A is before dependency B in effective POM, same should be true for classpath as well.
HTH T PS: Sorry for bloated answers, a I just spotted that this is user ML not dev ML.... On Thu, Jul 27, 2023 at 5:29 PM <mark.yagnatin...@barclays.com.invalid> wrote: > Thank you! I think my main takeaway here is that things (1) in flux (and > hopefully will improve in Maven 4) and (2) a bit complicated but > (3) I can still guarantee something comes first by listing it as the first > thing in the pom (is that right?) > > Thanks once more! > Mark. > > -----Original Message----- > From: Tamás Cservenák <ta...@cservenak.net> > Sent: Thursday, July 27, 2023 10:52 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. > 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/15t5z3XK8nENdtkfvA1F3?h=Efy8jMRjTS28CUJyvgBnMOlaMr07e6ETXpi8khKLG3k=&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/15t5pP8kDYsBp16pq3Cwo?h=8f2DByrPlQLfzEcejbPLFPQGuQ8TsuWhXGbnYcguXpQ=&u=https://github.com/apache/maven-resolver/blob/maven-resolver-1.9.14/maven-resolver-util/src/main/java/org/eclipse/aether/util/graph/visitor/PreorderNodeListGenerator.java > > The example output: > > https://clicktime.symantec.com/15t5jYwTkwBbQ4GuHUooB?h=T619edEwyisQy-KWGy3VvRfMFWDbZCgujjHUqdh8Wfg=&u=https://gist.github.com/cstamas/ca113c1d6697540a4cf55c3098b9a550 > > 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/15t5uDL2gAYnDwvkNbc6R?h=Oo9ciO2fkPcfkh29sRGMpRA_gqMZXDNvOTPIvINgw_A=&u=https://github.com/apache/maven-resolver/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/15t5ZtYtqhpQaAd4CN1Vw?h=XDVhSYMduTltP5c > > FPTLr7pXDMQ0hXrn_euWrugDjQoo=&u=http://people.apache.org/~jvanzyl/mave > > n-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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