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@objectql/plugin-formula

Formula engine plugin for ObjectQL - Evaluate JavaScript-style formulas with field references, system variables, and safe sandbox execution.

Overview

The Formula Plugin provides calculated field capabilities for ObjectQL applications. It enables you to define JavaScript-style expressions that compute values dynamically based on other fields, system variables, and custom functions.

Features

  • Field References: Access other fields in the same record (e.g., quantity * unit_price)
  • System Variables: Use built-in variables like $today, $current_user.id, $year
  • Lookup Chains: Navigate relationships (e.g., account.owner.name)
  • Built-in Functions: Access Math, String, Date methods
  • Conditional Logic: Use ternary operators and if/else statements
  • Safe Sandbox: Execute formulas in a controlled environment
  • Custom Functions: Register your own functions for use in formulas
  • Type Coercion: Automatic conversion to expected data types

Installation

pnpm add @objectql/plugin-formula

Usage

Basic Setup

import { ObjectStackKernel } from '@objectstack/runtime';
import { FormulaPlugin } from '@objectql/plugin-formula';

const kernel = new ObjectStackKernel([
  // Your application config
  myApp,
  
  // Add the formula plugin
  new FormulaPlugin({
    enable_cache: false,
    sandbox: {
      enabled: true,
      allowed_globals: ['Math', 'String', 'Number', 'Date']
    }
  })
]);

await kernel.start();

Defining Formula Fields

In your object metadata:

name: invoice_items
fields:
  quantity:
    type: number
  unit_price:
    type: currency
  
  # Calculated field
  total_amount:
    type: formula
    expression: "quantity * unit_price"
    data_type: currency
  
  # Using system variables
  days_since_created:
    type: formula
    expression: "Math.floor(($today - created_at) / (1000 * 60 * 60 * 24))"
    data_type: number

Configuration Options

interface FormulaPluginConfig {
  // Enable result caching
  enable_cache?: boolean;
  
  // Cache TTL in seconds
  cache_ttl?: number;
  
  // Custom functions registry
  custom_functions?: Record<string, Function>;
  
  // Sandbox configuration
  sandbox?: {
    enabled?: boolean;
    allowed_globals?: string[];
    blocked_operations?: string[];
  };
  
  // Auto-evaluate formulas on query
  autoEvaluateOnQuery?: boolean;
}

System Variables

Available system variables in formulas:

  • $today - Current date (midnight)
  • $now - Current timestamp
  • $year, $month, $day - Current date components
  • $hour, $minute, $second - Current time components
  • $current_user - Current user object with .id, .name, etc.
  • $is_new - Boolean indicating if this is a new record
  • $record_id - Current record ID

Examples

Conditional Formulas

discount:
  type: formula
  expression: "total_amount > 1000 ? total_amount * 0.1 : 0"
  data_type: currency

Lookup Chain Formulas

account_owner_email:
  type: formula
  expression: "account.owner.email"
  data_type: text

Custom Functions

const plugin = new FormulaPlugin({
  custom_functions: {
    formatCurrency: (value: number) => `$${value.toFixed(2)}`,
    calculateTax: (amount: number, rate: number) => amount * rate
  }
});

Security

The formula engine includes basic sandbox protection:

  • Blocks dangerous operations like eval, Function, require, import
  • Restricts access to allowed global objects
  • Note: For production use with untrusted formulas, consider additional sandboxing

API Reference

See the full API documentation for detailed information about:

  • FormulaEngine class
  • FormulaPlugin class
  • Type definitions
  • Error handling

License

MIT © ObjectStack Inc.