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67 lines
2.3 KiB
Markdown
67 lines
2.3 KiB
Markdown
## Moving the selection with syntax-aware motions
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`Alt-p`, `Alt-o`, `Alt-i`, and `Alt-n` (or `Alt` and arrow keys) allow you to move the
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selection according to its location in the syntax tree. For example, many languages have the
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following syntax for function calls:
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```js
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func(arg1, arg2, arg3);
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```
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A function call might be parsed by tree-sitter into a tree like the following.
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```tsq
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(call
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function: (identifier) ; func
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arguments:
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(arguments ; (arg1, arg2, arg3)
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(identifier) ; arg1
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(identifier) ; arg2
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(identifier))) ; arg3
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```
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Use `:tree-sitter-subtree` to view the syntax tree of the primary selection. In
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a more intuitive tree format:
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```
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┌────┐
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│call│
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┌─────┴────┴─────┐
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│ │
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┌─────▼────┐ ┌────▼────┐
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│identifier│ │arguments│
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│ "func" │ ┌────┴───┬─────┴───┐
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└──────────┘ │ │ │
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│ │ │
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┌─────────▼┐ ┌────▼─────┐ ┌▼─────────┐
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│identifier│ │identifier│ │identifier│
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│ "arg1" │ │ "arg2" │ │ "arg3" │
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└──────────┘ └──────────┘ └──────────┘
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```
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If you have a selection that wraps `arg1` (see the tree above), and you use
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`Alt-n`, it will select the next sibling in the syntax tree: `arg2`.
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```js
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// before
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func([arg1], arg2, arg3)
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// after
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func(arg1, [arg2], arg3);
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```
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Similarly, `Alt-o` will expand the selection to the parent node, in this case, the
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arguments node.
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```js
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func[(arg1, arg2, arg3)];
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```
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There is also some nuanced behavior that prevents you from getting stuck on a
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node with no sibling. When using `Alt-p` with a selection on `arg1`, the previous
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child node will be selected. In the event that `arg1` does not have a previous
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sibling, the selection will move up the syntax tree and select the previous
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element. As a result, using `Alt-p` with a selection on `arg1` will move the
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selection to the "func" `identifier`.
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[lang-support]: ./lang-support.md
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