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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For important disclosures, please see: https://www.cib.barclays/disclosures/sales-and-trading-disclaimer.html regarding marketing commentary from Barclays Sales and/or Trading desks, who are active market participants; https://www.cib.barclays/disclosures/barclays-global-markets-disclosures.html regarding our standard terms for Barclays Corporate and Investment Bank where we trade with you in principal-to-principal wholesale markets transactions; and in respect to Barclays Research, including disclosures relating to specific issuers, see: http://publicresearch.barclays.com. __________________________________________________________________________________ If you are incorporated or operating in Australia, read these important disclosures: https://www.cib.barclays/disclosures/important-disclosures-asia-pacific.html. __________________________________________________________________________________ For more details about how we use personal information, see our privacy notice: https://www.cib.barclays/disclosures/personal-information-use.html. __________________________________________________________________________________
