RFR: 5080391: ArrayIndexOutOfBounds during "undo" of Right-to-Left text insert [v2]

[Alexey Ivanov]

On Fri, 7 Oct 2022 09:01:35 GMT, Prasanta Sadhukhan <psadhukhan at openjdk.org> wrote:

> `getElement()` can return null [here](https://github.com/openjdk/jdk/blob/master/src/java.desktop/share/classes/javax/swing/text/AbstractDocument.java#L2619) and [here](https://github.com/openjdk/jdk/blob/master/src/java.desktop/share/classes/javax/swing/text/AbstractDocument.java#L2398) so it should not be enitrely impossible not to get null, so it should be a ok

I know it is possible _theoretically_. My point is for a valid offset in the document, this particular line must _never_ return `null`. If it does, the element tree is invalid. As such, we should rather catch the case of bad bidi element tree by throwing NPE rather than pretending nothing bad happened.

`BidiRootElement` is a `BranchElement`: https://github.com/openjdk/jdk/blob/096bca4a9c5e8ac2668dd965df92153ea1d80add/src/java.desktop/share/classes/javax/swing/text/AbstractDocument.java#L2700-L2713

And [`BranchElement.getElementIndex`](https://github.com/openjdk/jdk/blob/096bca4a9c5e8ac2668dd965df92153ea1d80add/src/java.desktop/share/classes/javax/swing/text/AbstractDocument.java#L2416-L2474) always returns a *valid* index.

So, I am against adding the `null`-check. It is not necessary here.

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PR: https://git.openjdk.org/jdk/pull/10446