New extension - Code Viewer

[ajbozarth]

Adds a new Elyra extension: Code Viewer

Code Viewer adds a command that will display a given chunk of
code (string) in a transient read-only "editor" without needing to
create a file.

The new command takes in a string of the code chunk or text to
display as well as an option mime type or extension to enable code
highlighting. It then opens a read-only "editor" containing the given
content. This allows for transient display of text without the need to
persist it to a file to display it to a user.

Frontend for #2549

Remaining To Do's:

• Add support for extensions in addition to mime types
• Remove temporary test code from pipeline editor

Developer's Certificate of Origin 1.1

   By making a contribution to this project, I certify that:

   (a) The contribution was created in whole or in part by me and I
       have the right to submit it under the Apache License 2.0; or

   (b) The contribution is based upon previous work that, to the best
       of my knowledge, is covered under an appropriate open source
       license and I have the right under that license to submit that
       work with modifications, whether created in whole or in part
       by me, under the same open source license (unless I am
       permitted to submit under a different license), as indicated
       in the file; or

   (c) The contribution was provided directly to me by some other
       person who certified (a), (b) or (c) and I have not modified
       it.

   (d) I understand and agree that this project and the contribution
       are public and that a record of the contribution (including all
       personal information I submit with it, including my sign-off) is
       maintained indefinitely and may be redistributed consistent with
       this project or the open source license(s) involved.

[elyra-bot]

Thanks for making a pull request to Elyra!

To try out this branch on binder, follow this link:

[ptitzler]

Would it be possible to enable the copy [to clipboard] action on the context menu?

Edit: it appears that users can use <cmd/ctrl><c> to copy selected text, so this is mostly a nice-to-have to improve usability.

[ajbozarth]

Would it be possible to enable the copy [to clipboard] action on the context menu?

I actually checked and I need to work on the context menu in general. If you open a md file then switch to a viewer the open preview option shows up and opens the preview for the md tab that was just open

[ptitzler]

Since there isn't anything code specific about the viewer's functionality, should we perhaps change the extension name to something more generic? For example, one might use the viewer to display plain text.

[ptitzler]

I've created a new label component:code-viewer in this repo to allow for proper classification of follow-up work.

[marthacryan]

Code LGTM - haven't tested locally

[ajbozarth]

I "solved" the context menu issues by simply disabling the jupyterlab context menu and letting the normal system context menu open when inside the viewer. (This lets users copy text).

I've also removed the test code so this is ready to merge. If further testing is desired you will want to check out the code then revert one commit to re-add the test code.

[ptitzler]

LGTM