Docs generated by Java8 Javadoc are incompatible with "javadoc -source 8"

[Roman Marchenko]

Hi Jon,

Thank you for the answer.

I'm wondering if it's possible to implement support for 'old' form of anchors while generating docs with '-source 8' option to make the docs compatible with Java8 docs. I guess this would make many people (which had issues with docs compatibility before, but didn't say about it) happy. Do you think it is a bad idea? Will it interfere the ongoing work of standardization?

There is another question related to this topic. It seems like Javadoc v11...15 cannot generate links to the external docs.oracle.com/javase/8/docs/api at all. So docs generated using ''-source 8' have no links to external documentation. There is JDK-8216497 which, I guess, fixed this for later versions, but I don't understand why it's not backported below. Are there any reasons to block backporting this to lower versions?

Of course, the problems above don't seem significant, however Javadoc seems inconsistent for now. So, I think, it'd be good to make it fixed if possible.

Best regards,
Roman

From: javadoc-dev <javadoc-dev-retn at openjdk.org> On Behalf Of Jonathan Gibbons
Sent: Friday, November 18, 2022 8:30 PM
To: javadoc-dev at openjdk.org
Subject: Re: Docs generated by Java8 Javadoc are incompatible with "javadoc -source 8"


Hi Roman,

TL;DR: The behavior is as expected.

If nothing else, note that `--source` describes the language level of the input source code, and has no relationship whatsoever to HTML version used for the output. This is somewhat similar to javac, where `--source` specifies the version of the input source files, and `--target` specifies the classfile version of the generated class files.

There are other major differences between JDK 8 javadoc and more recent versions.  More obvious than the version of HTML, there is the difference in the page layout: JDK 8 javadoc uses frames and predates the Search facility; later versions do not use frames, and provide the Search mechanism and more in-page links to aid with navigation.

The issue of the form of anchors generated by different versions is an interesting special case, with no easy solution at this time, other than to use compatible versions of javadoc for the API being cross-linked. There is no information available to the `-link` or `-linkoffline` options to know the form of anchors used in the documentation being linked to.

That being said, there is ongoing work to standardize _and specify_ the form of anchors and major structural elements to mitigate against problems going forward.

-- Jon
On 11/18/22 7:32 AM, Roman Marchenko wrote:
Hi,

As far as I know, Html4 support was removed from Javadoc a time ago. So now Javadoc generates html5-like anchors even with “-source 8” or “-release 8” option specified. There is JDK-8187521 added TestAnchorNames.testHtml5 which checks if Html5-like anchors are generated for “-source 8” option.

On the other hand, Java8’s Javadoc still supports html4 and doesn’t support html5. So it turns that docs generated by Java8’s Javadoc are not compatible with docs generated by any other (I guess starting from jdk17 and above) “Javadoc -release 8” because they use different types of anchors. So it’s impossible to use cross links in such cases.

I haven’t found any discussion explaining that, so could anyone explain, please, if it is correct behavior or not?

- Roman

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