FEEL Analyzer

A library for analyzing FEEL (Friendly Enough Expression Language) expressions.

Installation

npm install @bpmn-io/feel-analyzer

Usage

To get started, create a FeelAnalyzer instance:

import { FeelAnalyzer } from '@bpmn-io/feel-analyzer';

const analyzer = new FeelAnalyzer();

Analyze a FEEL expression to extract input variables:

const result = analyzer.analyzeExpression('x + y');

console.log(result.valid); // true
console.log(result.inputs);
// [
//   { name: 'x' },
//   { name: 'y' }
// ]

Configure the FEEL dialect (expression or unary tests):

const analyzer = new FeelAnalyzer({
  dialect: 'unaryTests' // defaults to 'expression'
});

Builtins

You can provide builtins and reservedNameBuiltins to exclude built-in names from input detection. Use @camunda/feel-builtins to supply these:

import { FeelAnalyzer } from '@bpmn-io/feel-analyzer';
import { builtins, reservedNameBuiltins } from '@camunda/feel-builtins';

const analyzer = new FeelAnalyzer({
  dialect: 'expression',
  parserDialect: 'camunda',
  builtins,
  reservedNameBuiltins
});

const result = analyzer.analyzeExpression('sum(orders.amount) > 100');

console.log(result.inputs);
// [
//   {
//     name: 'orders',
//     type: 'List',
//     entries: [
//       { name: 'amount' }
//     ]
//   }
// ]

Input Variables

The analyzer extracts input variables with type information, including nested structures. The data model is aligned with variable-resolver:

const result = analyzer.analyzeExpression('person.name = "John" and scores[1] > 10');

console.log(result.inputs);
// [
//   {
//     name: 'person',
//     type: 'Context',
//     entries: [
//       { name: 'name' }
//     ]
//   },
//   {
//     name: 'scores',
//     type: 'List'
//   }
// ]

Invoked Functions

The analyzer extracts all function invocations from the expression, sorted by name and deduplicated. Each function is classified as builtin or user based on the provided builtins list:

import { FeelAnalyzer } from '@bpmn-io/feel-analyzer';
import { camundaBuiltins, camundaReservedNameBuiltins } from '@camunda/feel-builtins';

const analyzer = new FeelAnalyzer({
  parserDialect: 'camunda',
  builtins: camundaBuiltins,
  reservedNameBuiltins: camundaReservedNameBuiltins
});

const result = analyzer.analyzeExpression('from json(sum(myHelper(x)))');

console.log(result.functions);
// [
//   { name: 'from json', type: 'builtin' },
//   { name: 'myHelper', type: 'user' },
//   { name: 'sum', type: 'builtin' }
// ]

Analyzing an Already-Parsed Tree

If you already have a parsed syntax tree—for example from a CodeMirror editor using the same parser—you can analyze it directly with analyzeTree, avoiding a redundant parse:

const analyzer = new FeelAnalyzer();

const expression = 'x + y';
const tree = analyzer.parser.parse(expression);

const result = analyzer.analyzeTree(tree, expression);

The tree must come from a parser configured consistently with the analyzer (same dialect, parserDialect, and reservedNameBuiltins) - such as the provided analyzer.parser. A tree parsed with a different configuration may yield incorrect results.

Related

• @bpmn-io/lezer-feel - FEEL language definition for the Lezer parser system

License

MIT