Steps to reproduce

Run mvn javadoc:javadoc against e.g. text-finder with Java 8.

Expected results

Note: These are the actual results when running with Java 11:

No warnings are printed:

[INFO] --- maven-javadoc-plugin:3.4.0:javadoc (default-cli) @ text-finder ---
[INFO] Configuration changed, re-generating javadoc.

Actual results

The following warning is printed:

[INFO] --- maven-javadoc-plugin:3.3.2:javadoc (default-cli) @ text-finder ---
[INFO] No previous run data found, generating javadoc.
[INFO] 
1 warning
[WARNING] Javadoc Warnings
[WARNING] javadoc: warning - Error fetching URL: https://javadoc.jenkins.io/

Evaluation

This is caused by the renaming of package-list to element-list in Java 10. I see https://javadoc.jenkins.io/element-list but https://javadoc.jenkins.io/package-list gives a 404 (Javadoc built with Java 11). In contrast, I see https://javadoc.jenkins.io/component/jenkins-test-harness/package-list but https://javadoc.jenkins.io/component/jenkins-test-harness/element-list gives a 404 (Javadoc built with Java 8). When element-list is copied to package-list, the warning disappears.

Solution

As long as both Java 8 and Java 11 builds continue to be supported (including supporting the ability to link against https://javadoc.jenkins.io), element-list must be copied to package-list as in gradle/gradle@5e88351dd456a5252d21f3a7ad25bff1b62a2fd2.