Treesitter

Introduction to Tree-sitter and Code Folding

Tree-sitter is a parsing library that provides fast, accurate syntax highlighting and code analysis by building a concrete syntax tree for your code. In LunarVim, Tree-sitter is pre-configured and powers advanced features like:

• Semantic syntax highlighting
• Smart code folding (collapsing/expanding code blocks)
• Refactoring-aware navigation

For JSON files, Tree-sitter understands nested objects, arrays, and key-value pairs, allowing you to fold sections of your JSON data logically. This is especially useful for large configuration files, API responses, or data dumps.

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Why Tree-sitter Folding for JSON?

Traditional folding in Vim relies on indentation or regex patterns, which often fail with complex nested JSON. Tree-sitter folding, however:

• Folds based on the actual syntax structure (e.g., objects, arrays).
• Handles nested hierarchies perfectly.
• Works instantly, with no manual setup in LunarVim.

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Setting Up Tree-sitter for JSON in LunarVim

LunarVim includes Tree-sitter by default, but ensure the JSON parser is installed:

1. Open LunarVim.
2. Run :LvimSyncCorePlugins to update parsers.
3. Verify JSON support with :TSInstallInfo (look for json in the list).

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Folding/Unfolding JSON: Keybindings

LunarVim uses Neovim’s native folding commands, enhanced by Tree-sitter. Use these default keybindings:

Action	Keybinding
Toggle fold at cursor	za
Close fold	zc
Open fold	zo
Close all folds	zM
Open all folds	zR
Fold level 1	z1
Fold level 2	z2
…	…

Custom LunarVim Shortcuts (if using Space as leader):

• Space + fc: Close all folds (zM)
• Space + fo: Open all folds (zR)

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Example: Folding a JSON File

Consider this JSON data:

{  
  "users": [  
    {  
      "id": 1,  
      "name": "Alice",  
      "roles": ["admin", "user"]  
    },  
    {  
      "id": 2,  
      "name": "Bob",  
      "roles": ["user"]  
    }  
  ]  
}  

Step-by-Step Workflow

1. Open the JSON file in LunarVim.
2. Navigate to a foldable block (e.g., the users array).
3. Press zc to collapse the array:

   {  
     "users": [ ... ],  
   }  

4. Press zo to expand it again.
5. Use zM to collapse all nested objects/arrays at once.

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Advanced Tips

1. Fold with Precision

• Fold specific levels: Use z2 to fold up to level 2 (e.g., collapse outer objects but leave inner arrays open).

2. Customize Fold Appearance

Add this to your config.lua to show fold indicators:

vim.opt.foldcolumn = '1'  -- Shows a fold indicator gutter  
vim.opt.fillchars = { fold = " " }  -- Cleaner look  

3. Use Fold Navigation

• Jump between folds with zj (next fold) and zk (previous fold).

4. Persist Folds

Add this to retain folds when closing/reopening files:

vim.opt.viewoptions:append('folds')  -- Save folds per file  

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Troubleshooting

• Folding not working? Run :TSUpdate json to update the JSON parser.
• Folds look incorrect? Ensure foldexpr is set to nvim_treesitter#foldexpr():

  vim.opt.foldmethod = 'expr'  
  vim.opt.foldexpr = 'nvim_treesitter#foldexpr()'  

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Conclusion

With Tree-sitter in LunarVim, managing JSON folding becomes intuitive and precise. Whether you’re working with massive configuration files or deeply nested API data, these keybindings and workflows will keep your workspace clutter-free.