From c99dffd011b259140baaefaf105f21a67bfafdc1 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Tue, 17 Mar 2026 11:30:37 +0000
Subject: [PATCH 1/2] Initial plan


From b4425502b90b6ebc54c7134d9804ce973fb61297 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Tue, 17 Mar 2026 11:39:53 +0000
Subject: [PATCH 2/2] Fix broken Eq/Ord semantics for AssetCapacity by
 implementing PartialEq via total_cmp

Co-authored-by: alexdewar <23149834+alexdewar@users.noreply.github.com>
---
 docs/release_notes/upcoming.md |  3 +++
 src/asset/capacity.rs          | 45 +++++++++++++++++++++++++++++++++-
 2 files changed, 47 insertions(+), 1 deletion(-)

diff --git a/docs/release_notes/upcoming.md b/docs/release_notes/upcoming.md
index 6d94973c4..3bb071243 100644
--- a/docs/release_notes/upcoming.md
+++ b/docs/release_notes/upcoming.md
@@ -54,6 +54,8 @@ ready to be released, carry out the following steps:
 - Users can now set demand to zero in `demand.csv` ([#871])
 - Fix: sign for levies of type `net` was wrong for inputs ([#969])
 - Fix `--overwrite` option for `save-graphs` command ([#1001])
+- Fix broken `Eq`/`Ord` consistency for `AssetCapacity`: equality is now aligned with
+  `total_cmp` ordering ([#1158])
 
 [#767]: https://github.com/EnergySystemsModellingLab/MUSE2/pull/767
 [#868]: https://github.com/EnergySystemsModellingLab/MUSE2/pull/868
@@ -72,3 +74,4 @@ ready to be released, carry out the following steps:
 [#1021]: https://github.com/EnergySystemsModellingLab/MUSE2/pull/1021
 [#1022]: https://github.com/EnergySystemsModellingLab/MUSE2/pull/1022
 [#1030]: https://github.com/EnergySystemsModellingLab/MUSE2/pull/1030
+[#1158]: https://github.com/EnergySystemsModellingLab/MUSE2/pull/1158
diff --git a/src/asset/capacity.rs b/src/asset/capacity.rs
index d0ae3127c..3e1382969 100644
--- a/src/asset/capacity.rs
+++ b/src/asset/capacity.rs
@@ -4,7 +4,7 @@ use std::cmp::Ordering;
 use std::ops::{Add, Sub};
 
 /// Capacity of an asset, which may be continuous or a discrete number of indivisible units
-#[derive(Clone, PartialEq, Copy, Debug)]
+#[derive(Clone, Copy, Debug)]
 pub enum AssetCapacity {
     /// Continuous capacity
     Continuous(Capacity),
@@ -13,6 +13,12 @@ pub enum AssetCapacity {
     Discrete(u32, Capacity),
 }
 
+impl PartialEq for AssetCapacity {
+    fn eq(&self, other: &Self) -> bool {
+        self.cmp(other) == Ordering::Equal
+    }
+}
+
 impl Add for AssetCapacity {
     type Output = Self;
 
@@ -213,4 +219,41 @@ mod tests {
         let got = orig.apply_limit_factor(factor);
         assert_eq!(got, AssetCapacity::Discrete(expected_units, unit_size));
     }
+
+    /// `PartialEq` must be consistent with `Ord`: two values are equal iff `cmp` returns
+    /// `Ordering::Equal`.
+    #[rstest]
+    #[case::continuous_equal(
+        AssetCapacity::Continuous(Capacity(1.0)),
+        AssetCapacity::Continuous(Capacity(1.0)),
+        true
+    )]
+    #[case::continuous_positive_zero_vs_negative_zero(
+        AssetCapacity::Continuous(Capacity(0.0)),
+        AssetCapacity::Continuous(Capacity(-0.0)),
+        false
+    )]
+    #[case::continuous_unequal(
+        AssetCapacity::Continuous(Capacity(1.0)),
+        AssetCapacity::Continuous(Capacity(2.0)),
+        false
+    )]
+    #[case::discrete_equal(
+        AssetCapacity::Discrete(3, Capacity(4.0)),
+        AssetCapacity::Discrete(3, Capacity(4.0)),
+        true
+    )]
+    #[case::discrete_unequal(
+        AssetCapacity::Discrete(2, Capacity(4.0)),
+        AssetCapacity::Discrete(3, Capacity(4.0)),
+        false
+    )]
+    fn eq_consistent_with_ord(
+        #[case] a: AssetCapacity,
+        #[case] b: AssetCapacity,
+        #[case] expected_eq: bool,
+    ) {
+        assert_eq!(a == b, expected_eq);
+        assert_eq!(a.cmp(&b) == Ordering::Equal, expected_eq);
+    }
 }