From 0311766a56d45bc02bbb2053531651e1bd85da7a Mon Sep 17 00:00:00 2001
From: Maneet Arvind Mehta <maneet.arvind@gmail.com>
Date: Wed, 14 Oct 2026 01:39:35 +0800
Subject: [PATCH] Add ToString override to DiffPiece

Shows position, sub-piece count, change type and text, so a
DiffPaneModel's Lines are readable in the debugger without expanding
each piece. Null-safe for Position, SubPieces and Text.

Fixes #84
---
 DiffPlex/DiffBuilder/Model/DiffPiece.cs |  7 +++++
 Facts.DiffPlex/DiffPieceFacts.cs        | 38 +++++++++++++++++++++++++
 2 files changed, 45 insertions(+)
 create mode 100644 Facts.DiffPlex/DiffPieceFacts.cs

diff --git a/DiffPlex/DiffBuilder/Model/DiffPiece.cs b/DiffPlex/DiffBuilder/Model/DiffPiece.cs
index 5dc5f4f9..39dac7aa 100644
--- a/DiffPlex/DiffBuilder/Model/DiffPiece.cs
+++ b/DiffPlex/DiffBuilder/Model/DiffPiece.cs
@@ -55,6 +55,13 @@ public override int GetHashCode()
             return hashCode;
         }
 
+        public override string ToString()
+        {
+            var position = Position?.ToString() ?? "-";
+            var subPieceCount = SubPieces?.Count ?? 0;
+            return $"Pos:{position,-6} Subs:{subPieceCount,-6} {Type,-16} {Text}";
+        }
+
         private bool SubPiecesEqual(DiffPiece other)
         {
             if (SubPieces is null)
diff --git a/Facts.DiffPlex/DiffPieceFacts.cs b/Facts.DiffPlex/DiffPieceFacts.cs
new file mode 100644
index 00000000..1604c7b6
--- /dev/null
+++ b/Facts.DiffPlex/DiffPieceFacts.cs
@@ -0,0 +1,38 @@
+using System.Collections.Generic;
+using DiffPlex.DiffBuilder.Model;
+using Xunit;
+
+namespace Facts.DiffPlex
+{
+    public class DiffPieceFacts
+    {
+        public class ToStringMethod
+        {
+            [Fact]
+            public void Will_include_position_sub_piece_count_type_and_text()
+            {
+                var piece = new DiffPiece("hello", ChangeType.Modified, 3);
+                piece.SubPieces.Add(new DiffPiece("h", ChangeType.Unchanged, 1));
+                piece.SubPieces.Add(new DiffPiece("ello", ChangeType.Inserted, 2));
+
+                Assert.Equal("Pos:3      Subs:2      Modified         hello", piece.ToString());
+            }
+
+            [Fact]
+            public void Will_show_dash_when_position_is_null()
+            {
+                var piece = new DiffPiece("text", ChangeType.Inserted);
+
+                Assert.Equal("Pos:-      Subs:0      Inserted         text", piece.ToString());
+            }
+
+            [Fact]
+            public void Will_not_throw_when_sub_pieces_and_text_are_null()
+            {
+                var piece = new DiffPiece { SubPieces = null };
+
+                Assert.Equal("Pos:-      Subs:0      Imaginary        ", piece.ToString());
+            }
+        }
+    }
+}