Hi everyone, Happy to see a JEP improving support for code snippets! I’ve got some feedback from the user perspective, and from some prototyping to support Javadoc snippet compilation:
> hide = regex — Would it be possible to have a simpler mechanism? For example, Rust code snippets use # at the beginning of the line to hide it [1]. From the user perspective, it is very easy to use and maintain — you don’t have to design a regex, you won’t get any surprises from its evaluation, or read/maintain some over-complicated pattern that slipped through code review. [1]: https://doc.rust-lang.org/rustdoc/documentation-tests.html#hiding-portions-of-the-example > lang=name — […] Valid names are java, properties and text Would it be possible to specify any language, as the goal seems to be to pass this information to any rendering tools? Some converter libraries might use snippets with configs (xml, json, …), some FFI libs — in C++/Rust, some libs might provide examples for some JVM-based languages. > region=name — Would it make sense to provide some kind of selectors for Java constructs? E.g., block:<method_name, or class_name> selecting the corresponding method or class? This plugin for Mkdocs does that, but it operates on text, not on AST, therefore, some unexpected curly braces break it (e.g., in string literals) [2]. However, even simple text-based selection works well. Does the Javadoc have the luxury of having ready access to the AST? Or is it too complex to implement/maintain? [2]: https://github.com/rnorth/mkdocs-codeinclude-plugin#usage > For inline snippets, especially those that are not a full compilation unit, it will be up to the test infrastructure to "wrap" the code fragment in a full compilation unit, such that it can be compiled and possibly executed. Would it be possible to keep the non-goal of not providing a standard tool to test them (to limit the scope of the JEP), but suggest a format/restrictions/expansion procedure on the snippets to support such test infra well (or enable adding it to JDK in the future)? I agree that external snippets work well (especially for large-ish fragments), but for some small things it is an overkill (you have to somehow configure the build system to build these files, but exclude from the final artifact, etc.), yet as a user I’d love to check their correctness. Would it make sense to: - Specify a standard way how a snippet is expanded (e.g., wrapped inside Callable#call, or some standard template — Java language designers are in a perfect position to pick a great one). [3] - Specify a set of tags that define the expectations of the expanded snippet behaviour (not sure it can be pulled into the scope, but the tools will require that information): [4] - Compiles/fails compilation - Runs successfully/Throws exception - Is totally ignored. In Rust doctests, for example, all these things are supported: [3] https://doc.rust-lang.org/rustdoc/documentation-tests.html#pre-processing-examples (adds main unless you do that) [4] https://doc.rust-lang.org/rustdoc/documentation-tests.html#attributes Finally, you might be interested in the previous attempts to implement such a tool for Java: https://github.com/jakewins/javadoctest Beware the docs aren’t updated, its current version does not require writing test manually, and finds and extracts snippets on itself, e.g.: https://github.com/jakewins/javadoctest/blob/master/junit-platform-engine/src/test/java/javadoctest/engine/fixture/FixtureDocTestSimple.java#L18-L22 -- Best regards, Dmitry Timofeev
