json-tool-lsp

json-tool-lsp

json-tool-lsp is a Zed extension for working with JSON buffers. It provides code actions for minifying and formatting the current editor buffer through a small companion LSP server.

The extension is adapted from the VSCode extension eriklynd.json-tools-1.0.2, with the editor integration rewritten for Zed. Because Zed extensions cannot read editor buffers directly, this extension uses LSP document synchronization to receive the current buffer text and returns WorkspaceEdit edits through code actions.

Features

• JSON Tool: Minify JSON

  • Replaces the current JSON buffer with compact JSON.
  • Supports one JSON value or a stream of multiple JSON values.
  • When multiple JSON values are present, the result is one minified JSON value per line.
  • Preserves large JSON numbers without converting them to floating point values.
  • Preserves object key order.

• JSON Tool: Format JSON

  • Uses a target maximum line length of 120 characters.
  • Formats the current JSON buffer with 4-space indentation.
  • Keeps arrays and objects on one line when they fit within the target line length.
  • Expands arrays and objects across multiple lines when they exceed the target line length.
  • Supports JSON streams, including JSON log files where each line is one JSON object.
  • Also supports irregular multi-line JSON objects when they can be parsed as a valid JSON value stream.

Supported Languages

The extension is enabled for:

• JSON
• JSONC

JSONC is currently parsed with the same parser as JSON, so comments and trailing commas are not accepted yet.

Usage

1. Open a JSON or JSONC file in Zed.
2. Open code actions for the current buffer.
3. Choose one of:
   • JSON Tool: Minify JSON
   • JSON Tool: Format JSON

If the buffer cannot be parsed as JSON, the extension does not offer a JSON edit.

JSON Streams

This extension intentionally supports more than a single top-level JSON value. This is useful for JSON log files and NDJSON-like files.

Input:

{"level":"info","message":"started"}
{"level":"warn","message":"slow request","duration_ms":1234}

Format output:

{"level": "info", "message": "started"}
{"level": "warn", "message": "slow request", "duration_ms": 1234}

Minify output:

{"level":"info","message":"started"}
{"level":"warn","message":"slow request","duration_ms":1234}

When a value is longer than the target line length, formatting expands it:

{
    "level": "info",
    "message": "a long message that pushes the object beyond the configured line width",
    "metadata": { "request_id": "abc", "status": 200 }
}

Local Development

For local development, this repository includes helper scripts that build the extension and copy only the extension manifest and wasm into the local Zed data directory:

scripts/install-dev.sh

For Zed Preview on macOS, pass the data directory explicitly:

scripts/install-dev.sh --data-dir "$HOME/Library/Application Support/Zed Preview"

Restart Zed after installation.

The script builds these local development artifacts:

• the Zed extension wasm
• the native json-tool-lsp server

It installs only the extension files into:

<Zed data dir>/extensions/installed/json-tool-lsp

The local LSP server is not bundled into the extension. Point Zed at the locally built server with lsp.json-tool-lsp.binary.path:

{
    "lsp": {
        "json-tool-lsp": {
            "binary": {
                "path": "/absolute/path/to/json-tool-lsp"
            }
        }
    }
}

These scripts are for local development only. Published builds download the platform-specific LSP server from GitHub Releases or use a user-provided server path.

Development Commands

Run LSP tests:

cargo test --manifest-path server/Cargo.toml

Build the extension wasm:

cargo build --release --target wasm32-wasip2

Build the LSP server:

cargo build --release --manifest-path server/Cargo.toml

Clean build outputs:

scripts/clean.sh

Uninstall the local development extension:

scripts/uninstall-dev.sh --data-dir "$HOME/Library/Application Support/Zed Preview"

LSP Server Resolution

At runtime, the Zed extension resolves json-tool-lsp in this order:

1. lsp.json-tool-lsp.binary.path from Zed settings.
2. json-tool-lsp from PATH.
3. A platform-specific binary downloaded from the latest GitHub Release.

Release Assets

For automatic downloads, GitHub Releases must include platform-specific zip assets with these names:

json-tool-lsp-macos-aarch64.zip
json-tool-lsp-macos-x86_64.zip
json-tool-lsp-linux-aarch64.zip
json-tool-lsp-linux-x86_64.zip
json-tool-lsp-windows-x86_64.zip

Each zip should contain exactly the native LSP binary:

json-tool-lsp

On Windows, the binary should be:

json-tool-lsp.exe

The included GitHub Actions workflow at .github/workflows/release-lsp.yml builds and uploads these assets when a tag matching v* is pushed, or when the workflow is run manually.

Configuration

All formatter settings are optional. If you do not configure anything, the extension uses its defaults.

You can configure only the setting you want to change:

{
    "lsp": {
        "json-tool-lsp": {
            "settings": {
                "max_line_length": 100
            }
        }
    }
}

Full formatter settings example:

{
    "lsp": {
        "json-tool-lsp": {
            "settings": {
                "indent_size": 4,
                "indent_style": "space",
                "max_line_length": 120,
                "compact_arrays": "auto",
                "compact_objects": "auto",
                "json_stream_mode": "auto",
                "document_separator": "\n",
                "trailing_newline": true,
                "object_key_order": "preserve",
                "space_after_colon": true,
                "space_after_comma": true
            }
        }
    }
}

Available formatter settings:

To use a custom LSP binary, configure Zed with:

{
    "lsp": {
        "json-tool-lsp": {
            "binary": {
                "path": "/absolute/path/to/json-tool-lsp"
            }
        }
    }
}

Implementation Notes

The LSP server uses full document synchronization. It stores the latest text for open JSON buffers and responds to textDocument/codeAction with WorkspaceEdit changes that replace the full document range.

Formatting is intentionally conservative:

• It parses valid JSON values with serde_json.
• It preserves object key order.
• It preserves arbitrary precision JSON numbers.
• It does not currently preserve comments, trailing commas, or other JSONC-only syntax.
• It does not read or write temporary files for JSON edits.

License

Apache-2.0