`CostLimit` is silently ignored and `ActualCost()` reports 0 when `OptTrackState` or `OptExhaustiveEval` is enabled

[miparnisari]

Describe the bug
Since v0.25.0, enabling cel.OptTrackState (or cel.OptExhaustiveEval) together with cel.CostLimit / cel.CostTracking silently disables runtime cost tracking:

• the cost limit is never enforced. Evaluation completes normally instead of returning EvalCancelledError{Cause: CostLimitExceeded};
• EvalDetails.ActualCost() returns a non-nil pointer to 0 instead of the real cost.

There is no error, no warning, and no API-level hint that the limit has been disabled. Code that relies on CostLimit as a DoS guard keeps running with the guard removed.

To Reproduce
Check which components this affects:

• parser
• checker
• interpreter

Sample expression and input that reproduces the issue:

a + b > 47

Test setup:

package main

import (
	"fmt"

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

func main() {
	env, err := cel.NewEnv(cel.Variable("a", cel.IntType), cel.Variable("b", cel.IntType))
	if err != nil {
		panic(err)
	}
	ast, iss := env.Compile("a + b > 47")
	if iss.Err() != nil {
		panic(iss.Err())
	}

	cases := []struct {
		name string
		opts []cel.ProgramOption
	}{
		{"CostLimit(1)", []cel.ProgramOption{cel.CostLimit(1)}},
		{"CostLimit(1)+OptTrackState", []cel.ProgramOption{cel.EvalOptions(cel.OptTrackState), cel.CostLimit(1)}},
		{"CostLimit(1)+OptExhaustiveEval", []cel.ProgramOption{cel.EvalOptions(cel.OptExhaustiveEval), cel.CostLimit(1)}},
		{"CostLimit(1)+OptPartialEval", []cel.ProgramOption{cel.EvalOptions(cel.OptPartialEval), cel.CostLimit(1)}},
		{"OptTrackCost", []cel.ProgramOption{cel.EvalOptions(cel.OptTrackCost)}},
		{"OptTrackCost+OptTrackState", []cel.ProgramOption{cel.EvalOptions(cel.OptTrackCost | cel.OptTrackState)}},
	}

	for _, tc := range cases {
		prg, err := env.Program(ast, tc.opts...)
		if err != nil {
			panic(err)
		}
		_, det, evalErr := prg.Eval(map[string]any{"a": 42, "b": 4})
		cost := "<nil>"
		if det != nil && det.ActualCost() != nil {
			cost = fmt.Sprint(*det.ActualCost())
		}
		fmt.Printf("%-34s err=%-46v actualCost=%s\n", tc.name, evalErr, cost)
	}
}

Expected behavior

CostLimit(1)                       err=operation cancelled: actual cost limit exceeded actualCost=2
CostLimit(1)+OptTrackState         err=operation cancelled: actual cost limit exceeded actualCost=2
CostLimit(1)+OptExhaustiveEval     err=operation cancelled: actual cost limit exceeded actualCost=2
CostLimit(1)+OptPartialEval        err=operation cancelled: actual cost limit exceeded actualCost=2
OptTrackCost                       err=<nil>                                          actualCost=4
OptTrackCost+OptTrackState         err=<nil>                                          actualCost=4

Actual behavior

CostLimit(1)                       err=operation cancelled: actual cost limit exceeded actualCost=2
CostLimit(1)+OptTrackState         err=<nil>                                          actualCost=0   <-- BUG
CostLimit(1)+OptExhaustiveEval     err=<nil>                                          actualCost=0   <-- BUG
CostLimit(1)+OptPartialEval        err=operation cancelled: actual cost limit exceeded actualCost=2
OptTrackCost                       err=<nil>                                          actualCost=4
OptTrackCost+OptTrackState         err=<nil>                                          actualCost=0   <-- BUG

Additional context
First seen in https://github.com/authzed/spicedb/actions/runs/32164309872/job/95800380925?pr=3269#step:4:102

[TristonianJones]

We actually just fixed this in #1419. As soon as @dmitriplotnikov finishes the module rename and redirects in #1413, we'll tag a new release.

[miparnisari]

Oh nice!

[TristonianJones]

Fixed in v0.32.0. Note, we updated the package name to the cel.dev/cel-go package, so your update may contain more deltas than usual.