Auto Indentation and Pairing

JLine provides features for auto-indentation and auto-pairing of brackets and quotes, which can enhance the user experience when writing multi-line commands or code snippets.

AutopairWidgets

A simple plugin that auto-closes, deletes and skips over matching delimiters in JLine. AutopairWidgets has been ported to JLine/Java from zsh-autopair.

Loading snippet: AutopairWidgetsExample...

Functionality

AutopairWidgets does 5 things for you:

1. It inserts matching pairs (by default, that means brackets, quotes and spaces):

   e.g. echo | => " => echo "|"

2. It skips over matched pairs:

   e.g. cat ./*.{py,rb|} => } => cat ./*.{py,rb}|

3. It auto-deletes pairs on backspace:

   e.g. git commit -m "|" => backspace => git commit -m |

4. And does all of the above only when it makes sense to do so. e.g. when the pair is balanced and when the cursor isn't next to a boundary character:

   e.g. echo "|"" => backspace => echo |"" (doesn't aggressively eat up too many quotes)

5. Spaces between brackets are expanded and contracted:

   e.g. echo [|] => space => echo [ | ] => backspace => echo [|]

Note: In above examples cursor position is marked as |.

Configuration

By default curly brackets {} are not paired by AutopairWidgets. Curly bracket pairing can be enabled by creating AutopairWidgets as:

AutopairWidgets autopairWidgets = new AutopairWidgets(reader, true);

Key Bindings

This plugin provides autopair-toggle widget that toggles between enabled/disabled autopair.

Auto Indentation

Command line auto indentation has been implemented in DefaultParser and LineReaderImpl classes.

Loading snippet: AutoIndentationExample...

Functionality

Widget accept-line calls Parser's method parser(...) that in case of unclosed brackets will throw EOFError exception that is caught by accept-line widget. EOFError exception contains necessary information to add indentation and the next closing bracket to the buffer.

Note that the last closing bracket must be entered manually even when option INSERT_BRACKET has been set to true.

Best Practices

When using auto-indentation and pairing in JLine, consider these best practices:

1. Selective Enabling: Enable these features only when they add value to the user experience, such as in REPL environments or code editors.

2. User Control: Always provide a way for users to toggle these features on/off.

3. Consistent Indentation: Use a consistent indentation size throughout your application.

4. Bracket Handling: Consider whether you want to include curly brackets in auto-pairing based on your application's needs.

5. Documentation: Document these features and their key bindings for your users.

6. Testing: Test these features with various input patterns to ensure they behave as expected.

7. Combine with Syntax Highlighting: These features work best when combined with syntax highlighting to provide visual feedback.

8. Language-Specific Configuration: Consider customizing these features based on the programming language or command syntax your application supports.