Add foldEndPattern to settings

[kylebarron]

Description of the Change

Add a value for foldEndPattern in the package settings. This improves the folding behavior for dictionaries, lists, and functions when not using the tree-sitter parser. 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 core 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.

Alternate Designs

The regex is ^\\s*\\}|^\\s*\\]|^\\s*\\) in order to fold the end of dictionaries, lists, and functions/tuples, respectively.

At first thought, it might be desirable to add ^\\s*""" to the regex in order to fold multi-line strings, but since the same characters are used to open a multiline string, this can create bugs. In fact, this used to be the value of foldEndPattern in this package, but was removed upon unintended effects used with Hydrogen.

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. A hacky solution to this was developed (read executed line to get indentation level and expand code nikitakit/hydrogen-python#10, code) in a Python-specific extension to Hydrogen, but the plugin's use is not widespread among all Hydrogen Python users.

Current Hydrogen behavior with ending character on separate line:

New Hydrogen behavior with ending character on separate line:

Possible Drawbacks

Those who prefer the current behavior could be disappointed? I can't think of any others.

Applicable Issues

• Atom/Hydrogen plugin: SyntaxError when creating multi-line dictionaries MagicStack/MagicPython#80
• SyntaxError when creating multi-line dictionaries nteract/hydrogen#724
• code is only considered a block if indent is maintained nteract/hydrogen#155

[rgbkrk]

This would be fantastic for us in nteract's hydrogen @maxbrunsfeld. 🙇 Thank you for all the Atoms.

[kylebarron]

Just pinging another maintainer @50Wliu. It would be great if this could be included in the next release of Atom.

[lee-dohm]

Would you mind taking a look at this when you get the chance @50Wliu ?

[kylebarron]

Just pinging again.

[winstliu]

Just a minor syntactic change to shorten the regex, but otherwise this looks good.

[winstliu]

Sorry for the delay!