Nestify — JSON Flatten & Nest

Turn nested JSON into flat dot-joined keys, and turn it back, without leaving the editor.

// before                          // after "Nestify: Flatten JSON"
{                                  {
  "app": {                           "app.name": "nestify",
    "name": "nestify",               "app.window.width": 800
    "window": { "width": 800 }     }
  }
}

Handy for i18n message files, .env-style config, flat key/value stores, and any diff that is easier to read one line per key.

How to use it

Select the JSON you want to convert, or select nothing to convert the whole file. Then pick whichever is closest to hand:

• Toolbar — on a .json file, two buttons sit top-right of the editor: flatten and nest.
• Right-click — Nestify → Flatten JSON / Unflatten (Nest) JSON.
• Command Palette — Cmd+Shift+P / Ctrl+Shift+P, then type Nestify.
• Sidebar — the Nestify icon in the Activity Bar lists every converter; click one to run it. It states what would be converted — key count and nesting depth of the file or your selection — and a converter that would not help right now says why instead of offering itself. Hovering a row reveals a copy button, which puts the result on the clipboard and leaves the file alone. Nestify: Copy Converted… does the same from the Command Palette.

Converting a selection leaves it selected, so you can see what changed; converting a whole file puts the cursor at the top of it. Invalid JSON changes nothing, tells you what is wrong, and puts the cursor on the character the parser stopped at.

JSON with comments is not supported: the conversion is written back with JSON.stringify, which would drop every comment in the file.

No shortcuts are bundled, so nothing of yours is overridden. To add your own, bind nestify.flatten or nestify.unflatten in Keyboard Shortcuts.

Settings

If your keys already contain dots, set nestify.separator to "/" or "_".

One thing to know about arrays

Flattening an array turns each index into a path segment, so { "tags": ["a"] } becomes { "tags.0": "a" }, and nesting turns it back into the array it came from. Keys that are not exactly the indices 0…n-1 — a gap, or "01" — stay an object, since no array could hold them without inventing values.

The one shape this cannot tell apart is an object whose keys already are "0", "1", … : it flattens the same way an array does, so it comes back as an array — including the file itself, which turns from an object into a JSON array when its own top-level keys are indices. Set nestify.arrays to "objects" if that is your data, and every container stays an object on the way back.

A key that already contains the separator is refused, because once joined it cannot be told from a path: flattening { "app": { "v1.2": { "x": 1 } } } would produce app.v1.2.x, which nests back four levels deep instead of the three that were written. The refusal names a separator the file leaves free and offers to set it for you, so one click converts the same file cleanly; nestify.separator takes whatever character you prefer if you would rather choose it yourself. Keys that clash, contain an empty segment, or use the reserved name __proto__ are refused too, in both directions, and the message names the key at fault. Whatever flattens can be nested back.

Nesting makes the same offer from the other side. A file whose keys are joined with something other than your separator — a .NET appsettings.json, whose paths use : and whose last segment is a dotted namespace like Serilog:MinimumLevel:Override:Microsoft.Extensions.Diagnostics — is refused under ., since the namespace splits and collides with the key beside it. The message offers the : those keys are actually written with, under which the file nests cleanly. It works the other way round just as well: with nestify.separator set to : for those config files, a dot-joined file has no key to split, so rather than handing it back unchanged Nestify offers the . it is written with. A file that is already nested has nothing to do under any separator, and converts quietly.

Contributing

Setup, architecture, and how to add a converter live in CONTRIBUTING.md.

License

MIT