refreshable v1: Add ToV2() and FromV2() conversion functions (#329)

* refreshable v1: Add ToV2() conversion function

* FromV2

refreshable/go.mod

@@ -4,6 +4,7 @@ go 1.20
 
 require (
 	github.com/palantir/pkg v1.1.0
+	github.com/palantir/pkg/refreshable/v2 v2.0.0
 	github.com/stretchr/testify v1.8.4
 )
 

refreshable/go.sum

@@ -2,6 +2,8 @@ github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/palantir/pkg v1.1.0 h1:0EhrSUP8oeeh3MUvk7V/UU7WmsN1UiJNTvNj0sN9Cpo=
 github.com/palantir/pkg v1.1.0/go.mod h1:KC9srP/9ssWRxBxFCIqhUGC4Jt7OJkWRz0Iqehup1/c=
+github.com/palantir/pkg/refreshable/v2 v2.0.0 h1:9uxG2L5nqUOfLg4l9YWjmh2JVW38VNXu0t4/mLkC2is=
+github.com/palantir/pkg/refreshable/v2 v2.0.0/go.mod h1:SfgGx/EeOCBJWfhDphHIu7nRl5TeXkKzvlfj8o7x9Mg=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/stretchr/testify v1.8.4 h1:CcVxjf3Q8PM0mHUKJCdn+eZZtm5yQwehR5yeSVQQcUk=

refreshable/v2.go

@@ -0,0 +1,30 @@
+// Copyright (c) 2023 Palantir Technologies. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package refreshable
+
+import (
+	refreshablev2 "github.com/palantir/pkg/refreshable/v2"
+)
+
+// ToV2 converts from a v1 Refreshable created by this package to v2 supporting type safety via generics.
+// If v1's value is not of type T, the function panics.
+func ToV2[T any](v1 Refreshable) refreshablev2.Refreshable[T] {
+	v2 := refreshablev2.New[T](v1.Current().(T))
+	v1.Subscribe(func(i interface{}) {
+		v2.Update(i.(T))
+	})
+	return v2
+}
+
+// FromV2 converts from a v1 Refreshable created by this package to v2 supporting type safety via generics.
+func FromV2[T any](v2 refreshablev2.Refreshable[T]) Refreshable {
+	v1 := NewDefaultRefreshable(v2.Current())
+	v2.Subscribe(func(i T) {
+		if err := v1.Update(i); err != nil {
+			panic(err)
+		}
+	})
+	return v1
+}

refreshable/v2_test.go

@@ -0,0 +1,25 @@
+// Copyright (c) 2023 Palantir Technologies. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package refreshable
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestToFromV2(t *testing.T) {
+	base := NewDefaultRefreshable("original")
+	v2 := ToV2[string](base)
+	v1 := FromV2(v2)
+	assert.Equal(t, base.Current(), "original", "base missing original value")
+	assert.Equal(t, v2.Current(), "original", "v2 missing original value")
+	assert.Equal(t, v1.Current(), "original", "v1 missing original value")
+
+	assert.NoError(t, base.Update("updated"))
+	assert.Equal(t, base.Current(), "updated", "base missing updated value")
+	assert.Equal(t, v2.Current(), "updated", "v2 missing updated value")
+	assert.Equal(t, v1.Current(), "updated", "v1 missing updated value")
+}