JSON Schema Validator VS Code Extension

A Visual Studio Code extension that validates JSON files against a JSON Schema using Ajv, displaying inline diagnostics and an output log.

Features

• 🎨 Settings UI: User-friendly configuration panel with visual controls
• 🌐 API Endpoint Support: Load schemas from remote URLs with automatic caching
• ⚡ Real-time Validation: Automatically validates as you type (debounced) and on save
• 🔍 Inline Diagnostics: Schema violations show up as red squiggles and entries in the Problems panel
• 🛠️ Smart Quick Fixes: Automated code actions to fix common schema violations
• 📋 Output Channel: Detailed validation logs appear in a dedicated JSON Validator output channel
• 🏗️ JSON Builder: Interactive tool to create valid JSON from your schema
• 🎭 Mustache Template Support: Validate JSON files with Mustache templates (.json.mustache files)

Prerequisites

• Node.js (>=12.x)
• The extension bundles its own CLI (validate.js); no separate global install required.

Installation

1. Clone or download this repository into your VS Code extensions folder:

   git clone https://github.com/yourusername/json-schema-validator.git
   

2. Navigate into the extension directory and install dependencies:

   cd json-schema-validator
   npm install
   

3. Build the extension:

   npm run build
   

4. Launch the extension in Development Host:

   • Open the project in VS Code.
   • Press F5 (or your configured debug shortcut).

Tip: If F5 triggers macOS dictation, enable Use F1, F2, etc. keys as standard function keys in System Settings → Keyboard.

Configuration

Using the Settings UI (Recommended)

1. Open the Command Palette (⌘⇧P or Ctrl+Shift+P)
2. Type and select "JSON Schema Validator: Configure Settings"
3. Choose between:
   • Local File: Load schema from a file in your workspace
   • Remote URL: Fetch schema from an API endpoint
4. Configure cache duration for remote schemas
5. Choose to save settings globally or per-workspace

Manual Configuration

Alternatively, you can edit your workspace or user settings directly:

// .vscode/settings.json
{
  // Option 1: Use a local file path
  "jsonSchemaValidator.schemaPath": "${workspaceFolder}/schemas/schema.json",
  
  // Option 2: Use an API endpoint (takes precedence over schemaPath)
  "jsonSchemaValidator.schemaUrl": "https://api.example.com/schema.json",
  
  // Cache duration for URL-based schemas (in seconds, default: 300)
  "jsonSchemaValidator.schemaCacheDuration": 300
}

• schemaPath: Path to your JSON Schema file. Can be absolute, relative to the workspace root, or a URL (http/https).
• schemaUrl: URL to fetch the JSON Schema from. If set, this takes precedence over schemaPath.
• schemaCacheDuration: Duration in seconds to cache schemas fetched from URLs (default: 300 seconds / 5 minutes).

Usage

Automatic Validation on Save

• Simply open any .json file in your workspace and save (⌘S).
• If the file violates the schema, you’ll see red squiggles and error messages in the Problems pane.

Manual Validation

1. Open the Command Palette (⌘⇧P).
2. Type and select "Validate JSON Against Schema".

Mustache Template Validation

The extension supports validating JSON files that contain Mustache template syntax:

1. Name your file with the .json.mustache extension (e.g., config.json.mustache)
2. The validator will automatically:
   • Detect mustache expressions like {{variableName}}
   • Replace them with appropriate sample values
   • Validate the resulting JSON against your schema
   • Map any errors back to the correct locations in your template

Example config.json.mustache:

{
  "apiUrl": "{{API_URL}}",
  "enabled": {{FEATURE_ENABLED}},
  "maxRetries": {{MAX_RETRIES}}
}

📚 For more details, see MUSTACHE_SUPPORT.md

Extension Commands

Extension Settings

Troubleshooting

• "Cannot find module 'minimist'": Run npm install in the extension folder.
• "No inputs were found in config file": Ensure your tsconfig.json includes "src/**/*.ts" and that your CLI code is under src/.
• macOS Function Keys: Enable function-key mode or remap Debug: Start Debugging in Keyboard Shortcuts.

License

This project is licensed under the MIT License.