RFR: 7070: Allow JMC to open compressed recordings with the extension .lz4

[Marcus Hirt]

On Thu, 20 May 2021 21:32:39 GMT, Alex Macdonald <aptmac at openjdk.org> wrote:

> This one-worder addresses JMC-7070 [[0]](https://bugs.openjdk.java.net/browse/JMC-7070), in which LZ4 compressed files cannot be opened while having the file extension ".lz4"
> 
> JMC-6701 added support for opening jfr files that were compressed using lz4 [[0]](https://github.com/openjdk/jmc/commit/b6e5bde2f45e7e44f252f42488332fc81b58506b). The functionality works, however the file association was not updated to include files ending in ".lz4" for flight recording files, so these compressed recordings must still be supplied with the file ending of ".jfr". This isn't ideal, because the default behaviour of `lz4` is to append ".lz4" to the end of the supplied file; in my example I have a file called `lol.jfr`, which when compressed becomes `lol.jfr.lz4` and cannot be opened by JMC without manually renaming it.
> 
> This one-word fix adds the file extension "lz4" to the extension list in `flightrecorder.ui`'s `plugin.xml` for `JfrEditor`, so that supplying a `*.lz4` file will result in trying to open a JfrEditor page.
> 
> [0] https://bugs.openjdk.java.net/browse/JMC-7070
> [1] https://github.com/openjdk/jmc/commit/b6e5bde2f45e7e44f252f42488332fc81b58506b
> 
> ### Before:
> - LZ4 does not exist as a valid file extension in the open file dialog
> ![0-before-opening](https://user-images.githubusercontent.com/10425301/119050175-7c314e00-b98f-11eb-91e6-540b8303d61b.png)
> - LZ4 does not have a valid file association in the preferences
> ![1-before-file-associations](https://user-images.githubusercontent.com/10425301/119050200-82272f00-b98f-11eb-99cd-c102729cae8a.png)
> - Dialog pops up complaining that no editor is associated with the file ending "lz4"
> ![2-before-opening](https://user-images.githubusercontent.com/10425301/119050186-7fc4d500-b98f-11eb-9cc3-cb37de6add2d.png)
> 
> ### After:
> - LZ4 is listed as a valid extension in the open file dialog
> ![2021-05-20-171807_192x239_scrot](https://user-images.githubusercontent.com/10425301/119050233-8fdcb480-b98f-11eb-873a-251e09d6a8ad.png)
> - LZ4 appears as a valid file extension in the preferences
> ![3-after-file-associations](https://user-images.githubusercontent.com/10425301/119050237-91a67800-b98f-11eb-9d86-3645bf5ff752.png)
> - Opening a LZ4 compressed recording works
> ![4-after-opened](https://user-images.githubusercontent.com/10425301/119050244-9539ff00-b98f-11eb-83fa-262fe47b2af7.png)

Marked as reviewed by hirt (Lead).

I think we should run with it for now. AFAIK no standard plug-in included in the Eclipse IDE distributions will use the lz4 extension. Also, it's becoming less common to run the Eclipse plug-in version of JMC.

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PR: https://git.openjdk.java.net/jmc/pull/250