add cancelable context variable syntax sugar to let package

let/std.go → let/let.go

@@ -2,11 +2,53 @@ package let
 
 import (
 	"context"
+	"fmt"
+	"reflect"
+	"testing"
 	"time"
 
 	"go.llib.dev/testcase"
+	"go.llib.dev/testcase/internal"
+	"go.llib.dev/testcase/random"
 )
 
+func With[V any, FN withFN[V]](s *testcase.Spec, fn FN) testcase.Var[V] {
+	var init testcase.VarInit[V]
+	switch fnv := any(fn).(type) {
+	case func() V:
+		init = func(t *testcase.T) V { return fnv() }
+	case func(testing.TB) V:
+		init = func(t *testcase.T) V { return fnv(t) }
+	case func(*testcase.T) V:
+		init = fnv
+	}
+	return testcase.Let(s, init)
+}
+
+type withFN[V any] interface {
+	func() V |
+		func(testing.TB) V |
+		func(*testcase.T) V
+}
+
+func As[To, From any](Var testcase.Var[From]) testcase.Var[To] {
+	asID++
+	fromType := reflect.TypeOf((*From)(nil)).Elem()
+	toType := reflect.TypeOf((*To)(nil)).Elem()
+	if !fromType.ConvertibleTo(toType) {
+		panic(fmt.Sprintf("you can't have %s as %s", fromType.String(), toType.String()))
+	}
+	return testcase.Var[To]{
+		ID: fmt.Sprintf("%s AS %T #%d", Var.ID, *new(To), asID),
+		Init: func(t *testcase.T) To {
+			var rFrom = reflect.ValueOf(Var.Get(t))
+			return rFrom.Convert(toType).Interface().(To)
+		},
+	}
+}
+
+var asID int // adds extra safety that there won't be a name collision between two variables
+
 func Context(s *testcase.Spec) testcase.Var[context.Context] {
 	return testcase.Let(s, func(t *testcase.T) context.Context {
 		ctx, cancel := context.WithCancel(context.Background())
@@ -15,6 +57,14 @@ func Context(s *testcase.Spec) testcase.Var[context.Context] {
 	})
 }
 
+func ContextWithCancel(s *testcase.Spec) (testcase.Var[context.Context], testcase.Var[func()]) {
+	return testcase.Let2(s, func(t *testcase.T) (context.Context, func()) {
+		ctx, cancel := context.WithCancel(context.Background())
+		t.Defer(cancel)
+		return ctx, cancel
+	})
+}
+
 func Error(s *testcase.Spec) testcase.Var[error] {
 	return testcase.Let(s, func(t *testcase.T) error {
 		return t.Random.Error()
@@ -86,3 +136,27 @@ func DurationBetween(s *testcase.Spec, min, max time.Duration) testcase.Var[time
 		return t.Random.DurationBetween(min, max)
 	})
 }
+
+func Contact(s *testcase.Spec, opts ...internal.ContactOption) testcase.Var[random.Contact] {
+	return testcase.Let[random.Contact](s, func(t *testcase.T) random.Contact {
+		return t.Random.Contact(opts...)
+	})
+}
+
+func FirstName(s *testcase.Spec, opts ...internal.ContactOption) testcase.Var[string] {
+	return testcase.Let(s, func(t *testcase.T) string {
+		return t.Random.Contact(opts...).FirstName
+	})
+}
+
+func LastName(s *testcase.Spec) testcase.Var[string] {
+	return testcase.Let(s, func(t *testcase.T) string {
+		return t.Random.Contact().LastName
+	})
+}
+
+func Email(s *testcase.Spec) testcase.Var[string] {
+	return testcase.Let(s, func(t *testcase.T) string {
+		return t.Random.Contact().Email
+	})
+}