Validate fittingSize for ListView.contentSize(in:for:)

CHANGELOG.md

@@ -8,6 +8,8 @@
 
 - [`Appearance.backgroundColor` now respects the current `UITraitCollection.userInterfaceStyle`](https://github.com/kyleve/Listable/pull/231). This means that the background color will default to `white` in light mode, and `black` in dark mode.
 
+- [Update `ListView.contentSize(in:for:)` to properly validate the provided `fittingSize`](TODO). This ensures that `.unconstrained` measurements along the wrong axis will now assert; instead of freeze.
+
 ### Added
 
 - [Introduce `onSelectionChanged` on `ListStateObserver`](https://github.com/kyleve/Listable/pull/223) to allow observing when the selected rows change.

ListableUI/Sources/ListView/ListSizing.swift

@@ -94,9 +94,25 @@ extension ListView
         /// for the layout. Only the cross-axis of the direction – width for vertical, and height for
         /// horizontal.
 
+        let unconstrainedValues : Set<CGFloat> = [0.0, .greatestFiniteMagnitude, .infinity]
+
         view.frame.size = view.collectionViewLayout.layout.direction.switch(
-            vertical: CGSize(width: fittingSize.width, height: 100.0),
-            horizontal: CGSize(width: 100.0, height: fittingSize.height)
+            vertical: {
+                precondition(
+                    unconstrainedValues.contains(fittingSize.width) == false,
+                    "Must provide a valid fitting width to measure vertically laid out lists. Instead, the width was '\(fittingSize.width)'."
+                )
+
+                return CGSize(width: fittingSize.width, height: 100.0)
+            },
+            horizontal: {
+                precondition(
+                    unconstrainedValues.contains(fittingSize.height) == false,
+                    "Must provide a valid fitting height to measure horizontally laid out lists. Instead, the height was '\(fittingSize.height)'."
+                )
+
+                return CGSize(width: 100.0, height: fittingSize.height)
+            }
         )
 
         let size = view.contentSize