From aa1f9756a1d113185d7d7f0e79001d3462e2387f Mon Sep 17 00:00:00 2001
From: Kevin Reid <kpreid@switchb.org>
Date: Mon, 11 Dec 2023 13:36:40 -0800
Subject: [PATCH] port: Allow creating an empty set.

---
 all-is-cubes-port/src/lib.rs | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/all-is-cubes-port/src/lib.rs b/all-is-cubes-port/src/lib.rs
index 1ac8d8bcd..8ef4d176a 100644
--- a/all-is-cubes-port/src/lib.rs
+++ b/all-is-cubes-port/src/lib.rs
@@ -105,7 +105,7 @@ pub async fn export_to_path(
 }
 
 /// Selection of the data to be exported.
-#[derive(Clone, Debug)]
+#[derive(Clone, Debug, Default)]
 pub struct ExportSet {
     /// `PartialUniverse` is defined in the `all_is_cubes` crate so that it can get access
     /// to the same serialization helpers as `Universe` and be guaranteed to serialize the
@@ -114,6 +114,11 @@ pub struct ExportSet {
 }
 
 impl ExportSet {
+    /// Set containing no elements.
+    pub fn empty() -> Self {
+        Self::default()
+    }
+
     /// Construct an [`ExportSet`] specifying exporting all members of the universe
     /// (insofar as that is possible).
     ///