More robust equals implementation

src/ImageSharp/Metadata/Profiles/XMP/XElementEqualityComparer.cs

@@ -0,0 +1,21 @@
+// Copyright (c) Six Labors.
+// Licensed under the Apache License, Version 2.0.
+
+using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
+using System.Xml.Linq;
+
+namespace SixLabors.ImageSharp.Metadata.Profiles.Xmp
+{
+    /// <summary>
+    /// Compare <see cref="XElement"/> objects for Name and Value equality.
+    /// </summary>
+    public class XElementEqualityComparer : IEqualityComparer<XElement>
+    {
+        /// <inheritdoc />
+        public bool Equals([AllowNull] XElement x, [AllowNull] XElement y) => x.Name == y.Name && x.Value == y.Value;
+
+        /// <inheritdoc />
+        public int GetHashCode([DisallowNull] XElement obj) => obj.GetHashCode();
+    }
+}

src/ImageSharp/Metadata/Profiles/XMP/XmpProfile.cs

@@ -3,6 +3,7 @@
 
 using System;
 using System.IO;
+using System.Linq;
 using System.Text;
 using System.Xml.Linq;
 
@@ -10,6 +11,7 @@ namespace SixLabors.ImageSharp.Metadata.Profiles.Xmp
 {
     /// <summary>
     /// Represents an XMP profile, providing access to the raw XML.
+    /// See <seealso href="https://www.adobe.com/devnet/xmp.html"/> for the full specification.
     /// </summary>
     public sealed class XmpProfile : IDeepCloneable<XmpProfile>
     {
@@ -29,6 +31,16 @@ namespace SixLabors.ImageSharp.Metadata.Profiles.Xmp
         /// <param name="data">The UTF8 encoded byte array to read the XMP profile from.</param>
         public XmpProfile(byte[] data) => this.Data = data;
 
+        /// <summary>
+        /// Initializes a new instance of the <see cref="XmpProfile"/> class, based on the speicief <see cref="XDocument"/>.
+        /// </summary>
+        /// <param name="doc">The document to base this instance on.</param>
+        public XmpProfile(XDocument doc)
+        {
+            this.document = doc;
+            this.UpdateData();
+        }
+
         /// <summary>
         /// Initializes a new instance of the <see cref="XmpProfile"/> class
         /// by making a copy from another XMP profile.
@@ -78,7 +90,7 @@ namespace SixLabors.ImageSharp.Metadata.Profiles.Xmp
                 return true;
             }
 
-            if (ReferenceEquals(left, null))
+            if (left is null)
             {
                 return false;
             }
@@ -95,10 +107,7 @@ namespace SixLabors.ImageSharp.Metadata.Profiles.Xmp
         /// True if the <paramref name="left"/> parameter is not equal to the <paramref name="right"/> parameter;
         /// otherwise, false.
         /// </returns>
-        public static bool operator !=(XmpProfile left, XmpProfile right)
-        {
-            return !(left == right);
-        }
+        public static bool operator !=(XmpProfile left, XmpProfile right) => !(left == right);
 
         /// <inheritdoc/>
         public XmpProfile DeepClone() => new(this);
@@ -113,7 +122,13 @@ namespace SixLabors.ImageSharp.Metadata.Profiles.Xmp
                 return;
             }
 
-            using var stream = new MemoryStream(this.Data.Length);
+            int initialLength = 256;
+            if (this.Data != null)
+            {
+                initialLength = this.Data.Length;
+            }
+
+            using var stream = new MemoryStream(initialLength);
             using var writer = new StreamWriter(stream, Encoding.UTF8);
             this.document.Save(writer);
             this.Data = stream.ToArray();
@@ -125,28 +140,37 @@ namespace SixLabors.ImageSharp.Metadata.Profiles.Xmp
         /// <inheritdoc />
         public override bool Equals(object obj)
         {
-            XmpProfile other = obj as XmpProfile;
-            if (ReferenceEquals(other, null))
+            if (obj is not XmpProfile other)
             {
                 return false;
             }
 
-            if (ReferenceEquals(this.Data, null))
+            XElement thisRoot = this.Document.Root;
+            XElement otherRoot = other.Document.Root;
+
+            return this.CompareElements(thisRoot, otherRoot);
+        }
+
+        private bool CompareElements(XElement left, XElement right)
+        {
+            var comparer = new XElementEqualityComparer();
+            bool result = comparer.Equals(left, right);
+            if (result)
             {
-                return false;
+                result |= !left.Elements().Except(right.Elements(), comparer).Any();
             }
 
-            return this.Data.Equals(other.Data);
+            return result;
         }
 
         private void InitializeDocument()
         {
-            if (this.document != null)
+            if (!(this.document is null))
             {
                 return;
             }
 
-            if (this.Data == null)
+            if (this.Data is null)
             {
                 return;
             }
@@ -164,6 +188,12 @@ namespace SixLabors.ImageSharp.Metadata.Profiles.Xmp
             using var stream = new MemoryStream(this.Data, 0, count);
             using var reader = new StreamReader(stream, Encoding.UTF8);
             this.document = XDocument.Load(reader);
+
+            // In case we removed any trailing bytes, update the Data property accordingly.
+            if (count != this.Data.Length)
+            {
+                this.UpdateData();
+            }
         }
     }
 }

tests/ImageSharp.Tests/Metadata/Profiles/XMP/XmpProfileTests.cs

@@ -1,6 +1,7 @@
 // Copyright (c) Six Labors.
 // Licensed under the Apache License, Version 2.0.
 
+using System;
 using System.IO;
 using System.Text;
 using System.Xml.Linq;
@@ -108,22 +109,36 @@ namespace SixLabors.ImageSharp.Tests.Metadata.Profiles.Xmp
         }
 
         [Fact]
-        public void XmpProfile_EqualalityIsByValue()
+        public void XmpProfile_EqualityIsByValue()
         {
             // arrange
-            byte[] content = new byte[0];
-            XmpProfile original = new XmpProfile(content);
-            XmpProfile other = new XmpProfile(content);
+            XmpProfile original = CreateMinimalXmlProfile();
+            var other = new XmpProfile(original.Data);
 
             // act
-            var equals = original.Equals(other);
-            var equality = original == other;
-            var inequality = original != other;
+            bool equals = original.Equals(other);
+            bool equality = original == other;
+            bool inequality = original != other;
 
             // assert
             Assert.True(equals);
             Assert.True(equality);
             Assert.False(inequality);
+            Assert.Equal(original, other);
+        }
+
+        [Fact]
+        public void XmpProfile_DocumentConstructor()
+        {
+            // arrange
+            XmpProfile original = CreateMinimalXmlProfile();
+
+            // act
+            var actual = new XmpProfile(original.Document);
+
+            // assert
+            XmpProfileContainsExpectedValues(actual);
+            Assert.Equal(original, actual);
         }
 
         [Fact]
@@ -147,7 +162,8 @@ namespace SixLabors.ImageSharp.Tests.Metadata.Profiles.Xmp
         {
             // arrange
             var image = new Image<Rgba32>(1, 1);
-            image.Metadata.XmpProfile = CreateMinimalXmlProfile();
+            XmpProfile original = CreateMinimalXmlProfile();
+            image.Metadata.XmpProfile = original;
             var encoder = new GifEncoder();
 
             // act
@@ -156,6 +172,7 @@ namespace SixLabors.ImageSharp.Tests.Metadata.Profiles.Xmp
             // assert
             XmpProfile actual = reloadedImage.Metadata.XmpProfile ?? reloadedImage.Frames.RootFrame.Metadata.XmpProfile;
             XmpProfileContainsExpectedValues(actual);
+            Assert.Equal(original, actual);
         }
 
         [Fact]
@@ -163,7 +180,8 @@ namespace SixLabors.ImageSharp.Tests.Metadata.Profiles.Xmp
         {
             // arrange
             var image = new Image<Rgba32>(1, 1);
-            image.Metadata.XmpProfile = CreateMinimalXmlProfile();
+            XmpProfile original = CreateMinimalXmlProfile();
+            image.Metadata.XmpProfile = original;
             var encoder = new JpegEncoder();
 
             // act
@@ -172,6 +190,7 @@ namespace SixLabors.ImageSharp.Tests.Metadata.Profiles.Xmp
             // assert
             XmpProfile actual = reloadedImage.Metadata.XmpProfile ?? reloadedImage.Frames.RootFrame.Metadata.XmpProfile;
             XmpProfileContainsExpectedValues(actual);
+            Assert.Equal(original, actual);
         }
 
         [Fact]
@@ -180,6 +199,7 @@ namespace SixLabors.ImageSharp.Tests.Metadata.Profiles.Xmp
             // arrange
             var provider = TestImageProvider<Rgba32>.File(TestImages.Jpeg.Baseline.ExtendedXmp);
             using Image<Rgba32> image = await provider.GetImageAsync(JpegDecoder);
+            XmpProfile original = image.Metadata.XmpProfile;
             var encoder = new JpegEncoder();
 
             // act
@@ -188,6 +208,7 @@ namespace SixLabors.ImageSharp.Tests.Metadata.Profiles.Xmp
             // assert
             XmpProfile actual = reloadedImage.Metadata.XmpProfile ?? reloadedImage.Frames.RootFrame.Metadata.XmpProfile;
             XmpProfileContainsExpectedValues(actual);
+            Assert.Equal(original, actual);
         }
 
         [Fact]
@@ -195,7 +216,8 @@ namespace SixLabors.ImageSharp.Tests.Metadata.Profiles.Xmp
         {
             // arrange
             var image = new Image<Rgba32>(1, 1);
-            image.Metadata.XmpProfile = CreateMinimalXmlProfile();
+            XmpProfile original = CreateMinimalXmlProfile();
+            image.Metadata.XmpProfile = original;
             var encoder = new PngEncoder();
 
             // act
@@ -204,6 +226,7 @@ namespace SixLabors.ImageSharp.Tests.Metadata.Profiles.Xmp
             // assert
             XmpProfile actual = reloadedImage.Metadata.XmpProfile ?? reloadedImage.Frames.RootFrame.Metadata.XmpProfile;
             XmpProfileContainsExpectedValues(actual);
+            Assert.Equal(original, actual);
         }
 
         [Fact]
@@ -211,7 +234,8 @@ namespace SixLabors.ImageSharp.Tests.Metadata.Profiles.Xmp
         {
             // arrange
             var image = new Image<Rgba32>(1, 1);
-            image.Frames.RootFrame.Metadata.XmpProfile = CreateMinimalXmlProfile();
+            XmpProfile original = CreateMinimalXmlProfile();
+            image.Frames.RootFrame.Metadata.XmpProfile = original;
             var encoder = new TiffEncoder();
 
             // act
@@ -220,6 +244,7 @@ namespace SixLabors.ImageSharp.Tests.Metadata.Profiles.Xmp
             // assert
             XmpProfile actual = reloadedImage.Metadata.XmpProfile ?? reloadedImage.Frames.RootFrame.Metadata.XmpProfile;
             XmpProfileContainsExpectedValues(actual);
+            Assert.Equal(original, actual);
         }
 
         [Fact]
@@ -227,7 +252,8 @@ namespace SixLabors.ImageSharp.Tests.Metadata.Profiles.Xmp
         {
             // arrange
             var image = new Image<Rgba32>(1, 1);
-            image.Metadata.XmpProfile = CreateMinimalXmlProfile();
+            XmpProfile original = CreateMinimalXmlProfile();
+            image.Metadata.XmpProfile = original;
             var encoder = new WebpEncoder();
 
             // act
@@ -236,6 +262,7 @@ namespace SixLabors.ImageSharp.Tests.Metadata.Profiles.Xmp
             // assert
             XmpProfile actual = reloadedImage.Metadata.XmpProfile ?? reloadedImage.Frames.RootFrame.Metadata.XmpProfile;
             XmpProfileContainsExpectedValues(actual);
+            Assert.Equal(original, actual);
         }
 
         private static void XmpProfileContainsExpectedValues(XmpProfile xmp)
@@ -249,7 +276,7 @@ namespace SixLabors.ImageSharp.Tests.Metadata.Profiles.Xmp
 
         private static XmpProfile CreateMinimalXmlProfile()
         {
-            string content = "<x:xmpmeta xmlns:x='adobe:ns:meta/'></x:xmpmeta><?xpacket end='w'?>";
+            string content = $"<?xpacket begin='' id='{Guid.NewGuid()}'?><x:xmpmeta xmlns:x='adobe:ns:meta/'></x:xmpmeta><?xpacket end='w'?>";
             byte[] data = Encoding.UTF8.GetBytes(content);
             var profile = new XmpProfile(data);
             return profile;