What happened

After the parser refactoring in #17977, promtool test rules no longer respects --enable-feature flags when loading rule files containing experimental PromQL syntax.

Root cause

In cmd/promtool/unittest.go, the testGroup.test() method creates a rules.ManagerOptions without setting the Parser field:

// cmd/promtool/unittest.go:252-258
opts := &rules.ManagerOptions{
    QueryFunc:  rules.EngineQueryFunc(suite.QueryEngine(), suite.Storage()),
    Appendable: suite.Storage(),
    Context:    context.Background(),
    NotifyFunc: func(context.Context, string, ...*rules.Alert) {},
    Logger:     promslog.NewNopLogger(),
    // Parser field is missing
}

The rules.NewManager then falls back to parser.NewParser(parser.Options{}), which has no experimental features enabled. Meanwhile, tg.parser (which does have the correct features) is only used for parsing expected samples (lines 485, 489) but not for loading the actual rule files.

Before #17977, the global parser.EnableExperimentalFunctions (etc.) was set in main() and respected by all parser.ParseExpr calls, including those inside the rules manager.

Expected behavior

promtool test rules --enable-feature=promql-experimental-functions test.yml should load rule files that use experimental PromQL functions.

Actual behavior

Rule files using experimental PromQL functions fail to load with parse errors.

Fix

Add Parser: tg.parser to the rules.ManagerOptions struct initialization.