I'd love less verbose XML. Gary
On Fri, Dec 11, 2020, 17:40 Will Iverson <wiver...@gmail.com> wrote: > One of the biggest complaints about Maven has long been the verbosity of > the XML format. The verbosity is due in large part to the exclusive > reliance on XML elements in Maven. > > Proposal: Allow Maven pom.xml to treat attributes as a short-hand for > declaring configuration elements. > > Example: One of the most verbose sections of the pom for most projects is > dependencies. A typical example: > > <dependency> > <groupId>commons-io</groupId> > <artifactId>commons-io</artifactId> > <version>2.8.0</version> > </dependency> > > Here is the same declaration expressed with attribute shortcuts: > > <dependency groupId="commons-io" artifactId="commons-io" version="2.8.0" /> > That's an 80% reduction in LoC, and would make Maven comparable with other > popular build tools (e.g. compare and contrast with other build tools at > https://mvnrepository.com/artifact/commons-io/commons-io/2.8.0) > > REQUEST: Feedback on if this is something to pursue. I've done some > research, happy to submit patches, but don't want to pursue if there is > either a) technical reason[s] not to proceed I'm not aware of or b) a lack > of enthusiasm for the entire idea from the community. > > Basically, I'm looking for some feedback along the lines of a) love it - > please submit patches so we can check it out, b) huh, maybe, willing to > look at it, or c) this is a terrible idea, because X. Effectively, a > totally non-binding vote on if this is worth exploring. > > I've discussed this with others online and done some research, so are a few > answers to objections/Qs as I currently understand. I may be > wrong/uninformed about certain aspects, which would be very helpful > feedback. > > Q: Won't this require a new Maven XSD to be generated? > A: No. The current Maven XSD declares many elements, but is not actually > involved in validation. While the current XSD is valuable for tools and > documentation, it does not actually perform validation. > > Q: Wait, so what actually does the validation? > A: It's all done in Java code generated by Modello. The maven-model project > (https://github.com/apache/maven/tree/maven-3.6.3/maven-model) relies on > the Modello Maven Plugin ( > http://codehaus-plexus.github.io/modello/modello-maven-plugin/) which in > turn relies on Modello core (http://codehaus-plexus.github.io/modello/) to > generate the Java code that processes the pom.xml > > The proposal is to submit a patch for Modello that would allow the > generated source to accept an attribute as an alias for input. If it's a > valid element per the Maven maven.mdo file ( > > https://github.com/apache/maven/blob/maven-3.6.3/maven-model/src/main/mdo/maven.mdo > ) > it will now accept an attribute as a shortcut. > > Q: Wouldn't this break, like, everything? > A: It would only affect pom.xml files that are read at runtime. All emitted > pom.xml files would remain exactly the same. > > Q: Does this involve changing or rewriting the user's pom.xml? Isn't that > the thing that's making it hard to support alternative formats for pom.xml > like polyglot poms, etc? > A: Nope, the pom.xml on disk is still the pom.xml. A > <prerequisites><maven>X.X.X<maven></prerequisites> would be the only flag > recommended to declare that a pom.xml uses attributes for shorthand. > > Q: How much work is this to actually implement? > A: It starts with a few lines added to the Modello code generation to allow > for attribute aliasing with a feature flag. Testing those changes through > the rest of the dependency chain. Adding test cases throughout. > Documentation. although as "now you can use attributes" is conceptually > simple it's not too bad. Tools in the Maven ecosystem would be able to > indicate they have been updated to support this by referring to the simple > term, "attribute shortcuts". Because nothing else changes, the only real > documentation change would be "things that were elements can also be > declared as attributes." The trickiest part is probably sorting out how to > manage the feature flag across the various components. I'm sure there's > more with a huge ecosystem like this, but the actual changes to the Modello > code gen appear to be surprisingly minor. > > Q: What about tooling, like IDEs, publishing to Maven Central & Maven > repositories, etc? > A: Many IDEs appear to have implemented validation logic on top of Maven > that currently will flag attributes as errors in a pom.xml. Those IDEs and > other tools would require updates to this validation logic. Because the > rendered pom.xml output remains the same publishing tool chains and Maven > repositories should be completely unaffected. > > Q: Any big issues you've identified? > A: Many sub-elements are not actually processed by Modello or Maven Model, > but are instead passed along to the plugin. For example, <configuration> > elements. It would be up to each of these projects to eventually allow for > attribute aliasing (or not). Maven projects that rely on Modello would have > the choice to adopt the new version and turn on the feature flag (or not). > It's possible that this would be confusing for some users - i.e. "why can I > declare dependencies with attributes but not configuration values"? That > said, I think it's manageable and would allow the ecosystem to slowly > update. > Q: Shouldn't we wait for Maven 5 to tackle this? > A: There's an issue going back to 2008 about the verbosity of pom.xml - > https://issues.apache.org/jira/browse/MNG-3397 - so... that's 12 years. > While writing this email, I just realized I commented on that issue back in > 2014. Any proposal to dramatically change the pom is going to be a *huge* > effort and is not at all what I'm proposing. This is literally the simplest > possible change I can think of that accomplishes the goal (dramatically > reducing the verbosity of the pom.xml) with the least possible impact to > the ecosystem. It's been twelve years. Maven 5 is years away. > > I know there is a voting system for changes to Maven, and this would be a > huge userland change. If there is even a soft exploratory "yes" I'm happy > to submit patches. Even better would be the assistance of an existing Maven > committer willing to help me navigate Apache requirements. If the feedback > is generally negative, that's fine too - I'll just go ahead and close the > issue. What I don't want to do is submit patches and then have everyone > yell at me. The Internet can be rough, you know. :) > > I know this is a long email - thanks for reading, and looking forward to > feedback. > > Thanks, > -Will > > P.S. I've been tracking my research on this approach with this issue > https://issues.apache.org/jira/browse/MNG-7044, in case you are curious > about the research/additional links. >
