Implement specter.UnwrapUnit (#28)

pkg/specter/unitloading.go

@@ -66,6 +66,15 @@ func UnitOf[T any](v T, id UnitID, kind UnitKind, source Source) *WrappingUnit[T
 	}
 }
 
+func UnwrapUnit[T any](unit Unit) (value T, ok bool) {
+	w, ok := unit.(*WrappingUnit[T])
+	if !ok {
+		return value, false
+	}
+
+	return w.wrapped, true
+}
+
 func (w *WrappingUnit[T]) ID() UnitID {
 	return w.id
 }

pkg/specter/unitloading_test.go

@@ -410,3 +410,40 @@ func TestUnitLoaderAdapter(t *testing.T) {
 		assert.Nil(t, units)
 	})
 }
+
+func TestUnwrapUnit(t *testing.T) {
+	type then[T any] struct {
+		value T
+		ok    bool
+	}
+	type testCase[T any] struct {
+		name string
+		when specter.Unit
+		then then[T]
+	}
+	tests := []testCase[string]{
+		{
+			name: "Unwrap of non wrapped unit should return zero value and false",
+			when: testutils.NewUnitStub("id", "kind", specter.Source{}),
+			then: then[string]{
+				value: "",
+				ok:    false,
+			},
+		},
+		{
+			name: "Unwrap of a wrapped unit should return the value and true",
+			when: specter.UnitOf("hello", "id", "kind", specter.Source{}),
+			then: then[string]{
+				value: "hello",
+				ok:    true,
+			},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			gotValue, gotOk := specter.UnwrapUnit[string](tt.when)
+			assert.Equal(t, tt.then.value, gotValue)
+			assert.Equal(t, tt.then.ok, gotOk)
+		})
+	}
+}