Invalid operator in expression sees `parse()` successfully

[davidjb]

Using the latest release of cel-js v0.8.2, I was attempting to see how the parser handled invalid expressions, and discovered that the following appears to parse successfully:

import { parse } from 'cel-js'
const result = parse("value =< 42") // Should be invalid syntax as =< is not an operator
console.log(result)

Output:

{
  isSuccess: true,
  cst: {
    name: 'expr',
    children: [Object: null prototype] { conditionalOr: [Array] }
  }
}

The expression is invalid expression as the operator =< does not exist - a real-world typo.

By contrast, this errors within Go, tested with https://github.com/google/cel-go v0.26.1:

package main

import (
	"log"

	"github.com/google/cel-go/cel"
)

func main() {
	env, err := cel.NewEnv()
	if err != nil {
		log.Fatal(err)
	}

	_, issues := env.Compile("value =< 42")
	if issues != nil && issues.Err() != nil {
		log.Fatalf("type-check error: %s", issues.Err())
	}
}

2025/09/30 09:57:03 type-check error: ERROR: <input>:1:7: Syntax error: token recognition error at: '=<'
 | value =< 42
 | ......^
ERROR: <input>:1:10: Syntax error: extraneous input '42' expecting <EOF>
 | value =< 42
 | .........^
exit status 1

[ChromeGG]

Hi @davidjb ,

Nice catch, legit bug.

Can you open PR to fix it? Currently I have very limited time, I don't now when it will be fixed 😬

[davidjb]

Thanks for getting back to me so quickly. Unfortunately, I'm not in a position to create a PR at this stage, I was just scouting for potential CEL libraries and encountered the issue as my very first call to parse(). Hopefully someone else can dive in and help you though!