From 2efcd4cf5ce245c9870755225600777a5671f261 Mon Sep 17 00:00:00 2001
From: Nick Entin <nick@portola.ai>
Date: Thu, 29 Aug 2024 17:54:19 -0700
Subject: [PATCH] Replace assertions in slice method with alert func

---
 Paralayout/GeometryAdditions.swift | 44 ++++++++++++++++++++++++------
 Paralayout/ParalayoutLog.swift     | 20 ++++++++++++++
 Paralayout/UIView+Alignment.swift  |  2 --
 3 files changed, 56 insertions(+), 10 deletions(-)
 create mode 100644 Paralayout/ParalayoutLog.swift

diff --git a/Paralayout/GeometryAdditions.swift b/Paralayout/GeometryAdditions.swift
index 9d0e3ac..39d1f1f 100644
--- a/Paralayout/GeometryAdditions.swift
+++ b/Paralayout/GeometryAdditions.swift
@@ -14,6 +14,7 @@
 //  limitations under the License.
 //
 
+import os
 import UIKit
 
 // MARK: - Operator Overloads
@@ -144,6 +145,8 @@ extension CGRect {
     
     /// Divides the receiver in two.
     ///
+    /// The `slice` will always have a length of the specified `amount` in the perpendicular axis to the `edge`. The `remainder` will have the length remaining along that axis, clamped to zero if the `amount` is longer than the receiver's length.
+    ///
     /// - parameter from: The edge from which the amount is interpreted.
     /// - parameter amount: The size of the slice (absolute).
     /// - returns: A tuple (slice: A rect with a width/height of the `amount`, remainder: A rect with a width/height of
@@ -152,34 +155,42 @@ extension CGRect {
         switch edge {
         case .minXEdge:
             // Left.
-            assert(amount <= width, "Cannot slice rect \(self) at edge \(edge) by \(amount)!")
+            if amount > width {
+                ParalayoutAlertForInvalidSliceDimensions()
+            }
             return (
                 CGRect(x: minX, y: minY, width: amount, height: height),
-                CGRect(x: minX + amount, y: minY, width: width - amount, height: height)
+                CGRect(x: minX + amount, y: minY, width: max(width - amount, 0), height: height)
             )
             
         case .minYEdge:
             // Top.
-            assert(amount <= height, "Cannot slice rect \(self) at edge \(edge) by \(amount)!")
+            if amount > height {
+                ParalayoutAlertForInvalidSliceDimensions()
+            }
             return(
                 CGRect(x: minX, y: minY, width: width, height: amount),
-                CGRect(x: minX, y: minY + amount, width: width, height: height - amount)
+                CGRect(x: minX, y: minY + amount, width: width, height: max(height - amount, 0))
             )
             
         case .maxXEdge:
             // Right.
-            assert(amount <= width, "Cannot slice rect \(self) at edge \(edge) by \(amount)!")
+            if amount > width {
+                ParalayoutAlertForInvalidSliceDimensions()
+            }
             return(
                 CGRect(x: maxX - amount, y: minY, width: amount, height: height),
-                CGRect(x: minX, y: minY, width: width - amount, height: height)
+                CGRect(x: minX, y: minY, width: max(width - amount, 0), height: height)
             )
             
         case .maxYEdge:
             // Bottom.
-            assert(amount <= height, "Cannot slice rect \(self) at edge \(edge) by \(amount)!")
+            if amount > height {
+                ParalayoutAlertForInvalidSliceDimensions()
+            }
             return(
                 CGRect(x: minX, y: maxY - amount, width: width, height: amount),
-                CGRect(x: minX, y: minY, width: width, height: height - amount)
+                CGRect(x: minX, y: minY, width: width, height: max(height - amount, 0))
             )
         }
     }
@@ -282,3 +293,20 @@ extension NSDirectionalEdgeInsets {
     }
 
 }
+
+// MARK: -
+
+nonisolated
+private func ParalayoutAlertForInvalidSliceDimensions() {
+    os_log(
+        "%@",
+        log: ParalayoutLog,
+        type: .default,
+        """
+        Paralayout detected a slice with an `amount` larger than the receiver's length in the specified axis. \
+        Set a symbolic breakpoint for \"ParalayoutAlertForInvalidSliceDimensions\" to debug. \
+        Call stack:
+        \(Thread.callStackSymbols.dropFirst(1).joined(separator: "\n"))
+        """
+    )
+}
diff --git a/Paralayout/ParalayoutLog.swift b/Paralayout/ParalayoutLog.swift
new file mode 100644
index 0000000..de629fb
--- /dev/null
+++ b/Paralayout/ParalayoutLog.swift
@@ -0,0 +1,20 @@
+//
+//  Copyright © 2024 Block, Inc.
+//
+//  Licensed under the Apache License, Version 2.0 (the "License");
+//  you may not use this file except in compliance with the License.
+//  You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+//  Unless required by applicable law or agreed to in writing, software
+//  distributed under the License is distributed on an "AS IS" BASIS,
+//  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+//  See the License for the specific language governing permissions and
+//  limitations under the License.
+//
+
+import os
+
+nonisolated
+internal let ParalayoutLog = OSLog(subsystem: "com.squareup.Paralayout", category: "layout")
diff --git a/Paralayout/UIView+Alignment.swift b/Paralayout/UIView+Alignment.swift
index a6e5564..0b8c7ed 100644
--- a/Paralayout/UIView+Alignment.swift
+++ b/Paralayout/UIView+Alignment.swift
@@ -170,8 +170,6 @@ extension AlignmentContext {
 
 // MARK: -
 
-@MainActor
-private let ParalayoutLog = OSLog(subsystem: "com.squareup.Paralayout", category: "layout")
 
 /// Triggered when an alignment method is called that uses mismatched position types, i.e. aligning a view's leading or
 /// trailing edge to another view's left or right edge, or vice versa. This type of mismatch is likely to look correct