Moving the selection with syntax-aware motions

Alt-p, Alt-o, Alt-i, and Alt-n (or Alt and arrow keys) allow you to move the selection according to its location in the syntax tree. For example, many languages have the following syntax for function calls:

func(arg1, arg2, arg3);

A function call might be parsed by tree-sitter into a tree like the following.

(call function: (identifier) ; func arguments: (arguments ; (arg1, arg2, arg3) (identifier) ; arg1 (identifier) ; arg2 (identifier))) ; arg3

Use :tree-sitter-subtree to view the syntax tree of the primary selection. In a more intuitive tree format:

┌────┐ │call│ ┌─────┴────┴─────┐ │ │ ┌─────▼────┐ ┌────▼────┐ │identifier│ │arguments│ │ "func" │ ┌────┴───┬─────┴───┐ └──────────┘ │ │ │ │ │ │ ┌─────────▼┐ ┌────▼─────┐ ┌▼─────────┐ │identifier│ │identifier│ │identifier│ │ "arg1" │ │ "arg2" │ │ "arg3" │ └──────────┘ └──────────┘ └──────────┘

If you have a selection that wraps arg1 (see the tree above), and you use Alt-n, it will select the next sibling in the syntax tree: arg2.

// before func([arg1], arg2, arg3) // after func(arg1, [arg2], arg3);

Similarly, Alt-o will expand the selection to the parent node, in this case, the arguments node.

func[(arg1, arg2, arg3)];

There is also some nuanced behavior that prevents you from getting stuck on a node with no sibling. When using Alt-p with a selection on arg1, the previous child node will be selected. In the event that arg1 does not have a previous sibling, the selection will move up the syntax tree and select the previous element. As a result, using Alt-p with a selection on arg1 will move the selection to the "func" identifier.