Feature Request: Option to Always Expand JSON Objects to Multiline

[jdwillemse]

Summary

Currently, Biome formats JSON objects inline when they fit within the configured lineWidth. There is no configuration option to force all JSON objects to be expanded into multiline form.

I would like to request an option to always expand JSON objects, regardless of line width.

Current Behavior

Given:

{ "a": 1, "b": 2 }

Biome keeps this inline if it fits within lineWidth.

Expected Behavior

With a configuration option enabled (for example json.formatter.objectExpand: "always"), the same input would format as:

{
  "a": 1,
  "b": 2
}

Even if the object would fit on a single line.

Use Case

• Improved readability in configuration files (package.json, tsconfig.json, etc.)
• Cleaner diffs in version control
• Enforcing a consistent multiline JSON style across a codebase
• Parity with workflows that previously relied on Prettier with aggressive wrapping

Proposed Configuration (Example)

{
  "json": {
    "formatter": {
      "objectExpand": "always"
    }
  }
}

Alternative naming could be:

• objectWrap: "always"
• multilineObjects: true
• Extend existing expand behavior to support "always"

Additional Context

Currently, reducing lineWidth is the only workaround, but this affects all formatting and is not JSON-specific.

It would be helpful to have a dedicated JSON formatting option for this behavior.

I think it would be good to also include an option for whether or not to handle arrays in the same way but I don't want to increase the scope of this request at this time

[Netail]

I think we already have such option: https://biomejs.dev/reference/configuration/#formatterexpand (set to "aways")

[siketyan]

I think we can extend the option to enable expanding for only objects or arrays

[derekcarepa]

I proposed something similar in #8305 — separate expand settings for arrays and objects. This would be a good addition.