Add foldEndPattern to settings to improve folding and Hydrogen selections

[kylebarron]

(I sent similar PRs to the language-python atom/language-python#274, and MagicPython MagicStack/MagicPython#161 syntax highlighters)

Note: I don't understand Julia's syntax too well, so the exact regular expression used in foldEndPattern is subject to debate. Regardless, this addition would serve Hydrogen+IJulia users.

Description of the Change

Add a value for foldEndPattern in the package settings. The regex used is ^\\s*\\]|^\\s*\\) in order to fold the end of arrays and functions. It folds the entire logical syntax item instead of leaving the ending character on a separate line. It also improves the use of Hydrogen when the ending ), or ] is on a separate line and not indented.

Many other Atom language grammars have a foldEndPattern; the regex used in this PR is taken from language-javascript because of the similarity in syntax used for data structures.

Benefits

1. Improve fold behavior by including the ending character (see screenshots below)

Expanded:

Current fold behavior:

New fold behavior:

2. This would also improve behavior with the Hydrogen package, as that uses Atom's fold regions to decide what block of code to send to the Jupyter kernel. (Currently you have to manually select the entire block in these cases).

Current Hydrogen behavior with ending character on separate line:

New Hydrogen behavior with ending character on separate line:

Applicable Issues

These issues refer to Python, but the same behavior exists when using IJulia.

• SyntaxError when creating multi-line dictionaries nteract/hydrogen#724
• code is only considered a block if indent is maintained nteract/hydrogen#155

[kylebarron]

Since Julia uses end to delimit the end of function definitions, it might be helpful to add ^\\s*end to the regex as well.

[pfitzseb]

Huh, interesting, I didn't even know this setting existed. Thanks for the PR!

I'll go ahead with merging this and will iterate on it in a future PR.

[kylebarron]

Yeah, I only discovered it when I was trying to debug why JavaScript in hydrogen ran blocks more accurately than Python. And I discovered it was because of this setting.