random: make RandomChoice fall back to the global RNG

Author: lmb

random/random.go

@@ -19,6 +19,8 @@ import (
 )
 
 // GetRandom returns a uint64 value chosen by Antithesis. You should not store this value or use it to seed a PRNG, but should use it immediately.
+//
+// Deprecated: Use [NewSource] instead.
 func GetRandom() uint64 {
 	return internal.Get_random()
 }
@@ -46,3 +48,15 @@ func (source) Uint64() uint64 {
 func NewSource(seed int64) rand.Source {
 	return source{}
 }
+
+// RandomChoice returns a randomly chosen item from a list of options. You should not store this value, but should use it immediately.
+func RandomChoice[T any](things []T) T {
+	numThings := len(things)
+	if numThings == 0 {
+		var nullThing T
+		return nullThing
+	}
+
+	index := rand.New(NewSource(0)).Intn(numThings)
+	return things[index]
+}

random/random_choice.go

@@ -13,3 +13,14 @@ func GetRandom() uint64 {
 func NewSource(seed int64) rand.Source {
 	return rand.NewSource(seed)
 }
+
+func RandomChoice[T any](things []T) T {
+	numThings := len(things)
+	if numThings == 0 {
+		var nullThing T
+		return nullThing
+	}
+
+	index := rand.Intn(numThings)
+	return things[index]
+}