[jdk18] RFR: 8206181: ExceptionInInitializerError: improve handling of exceptions in user-provided taglets

[Pavel Rappo]

Using a custom taglet may result in exceptions, not all of which are javadoc bugs. Some of these exceptions are taglet bugs.

It was noticed that an exception in a static initializer of a custom taglet looks like a javadoc bug, which it is not. The fix was to trivially catch java.lang.ExceptionInInitializerError and translate it into an error like it is already done for some other exceptions.

While working on this fix, I noticed that there were no tests that cover various exceptions that could arise while registering a taglet:

  * ClassNotFoundException
  * NoSuchMethodException
  * InstantiationException
  * InvocationTargetException

I added a test to cover all of those as well as ExceptionInInitializerError and ClassCastException, which I proactively handled similarly to ExceptionInInitializerError.

I note that a typical taglet-registration error message is quite poor and should be improved in the future. For example, it is unclear that the method that javadoc cannot find is the nullary (i.e. parameterless or no-arg) MyTaglet constructor:

    Error - Exception java.lang.NoSuchMethodException thrown while trying to register Taglet MyTaglet...

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Commit messages:
 - Merge branch 'openjdk:master' into 8206181
 - Initial commit

Changes: https://git.openjdk.java.net/jdk18/pull/44/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk18&pr=44&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8206181
  Stats: 442 lines in 8 files changed: 430 ins; 11 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk18/pull/44.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk18 pull/44/head:pull/44

PR: https://git.openjdk.java.net/jdk18/pull/44