Refactor hashing logic and add test cases

Author: MaggieKimani1

src/Microsoft.OpenApi/Models/OpenApiDocument.cs

@@ -1,4 +1,4 @@
-// Copyright (c) Microsoft Corporation. All rights reserved.
+// Copyright (c) Microsoft Corporation. All rights reserved.
 // Licensed under the MIT license. 
 
 using System;
@@ -65,6 +65,11 @@ public class OpenApiDocument : IOpenApiSerializable, IOpenApiExtensible
         /// </summary>
         public IDictionary<string, IOpenApiExtension> Extensions { get; set; } = new Dictionary<string, IOpenApiExtension>();
 
+        /// <summary>
+        /// The unique hash code of the generated OpenAPI document
+        /// </summary>
+        public string HashCode => GenerateHashValue(this);
+
         /// <summary>
         /// Parameter-less constructor
         /// </summary>
@@ -379,21 +384,35 @@ public IOpenApiReferenceable ResolveReference(OpenApiReference reference)
         }
 
         /// <summary>
-        /// Uses the stream input to generate the hash value of an OpenApi document 
+        /// Takes in an OpenApi document instance and generates its hash value 
         /// </summary>
-        /// <param name="input">Stream containing OpenAPI description to hash.</param>
+        /// <param name="doc">The OpenAPI description to hash.</param>
         /// <returns>The hash value.</returns>
-        public static string GenerateHashValue(Stream input)
+        public static string GenerateHashValue(OpenApiDocument doc)
         {
             HashAlgorithm sha = SHA512.Create();
-            byte[] result = sha.ComputeHash(input);
+            using var memoryStream = new MemoryStream();
+
+            using var cryptoStream = new CryptoStream(memoryStream, sha, CryptoStreamMode.Write);
+            using var streamWriter = new StreamWriter(cryptoStream);
+
+            var openApiJsonWriter = new OpenApiJsonWriter(streamWriter, new OpenApiJsonWriterSettings { Terse = true });
+            doc.SerializeAsV3(openApiJsonWriter);
+            openApiJsonWriter.Flush();
 
+            var hash = memoryStream.ToArray();
+
+            return ConvertByteArrayToString(hash);
+        }
+
+        private static string ConvertByteArrayToString(byte[] hash)
+        {
             // Build the final string by converting each byte
             // into hex and appending it to a StringBuilder
             StringBuilder sb = new StringBuilder();
-            for (int i = 0; i < result.Length; i++)
+            for (int i = 0; i < hash.Length; i++)
             {
-                sb.Append(result[i].ToString("X2"));
+                sb.Append(hash[i].ToString("X2"));
             }
 
             return sb.ToString();

test/Microsoft.OpenApi.Tests/Microsoft.OpenApi.Tests.csproj

@@ -36,6 +36,20 @@
   </ItemGroup>
 
   <ItemGroup>
+    <EmbeddedResource Include="Models\Samples\sampleDocument.yaml">
+    <CopyToOutputDirectory>Always</CopyToOutputDirectory>
+    </EmbeddedResource>
+    <EmbeddedResource Include="Models\Samples\sampleDocumentWithWhiteSpaces.yaml">
+        <CopyToOutputDirectory>Always</CopyToOutputDirectory>
+    </EmbeddedResource>
+  </ItemGroup>
+
+  <ItemGroup>
+      
     <None Update="PublicApi\PublicApi.approved.txt" CopyToOutputDirectory="Always" />
   </ItemGroup>
+
+  <ItemGroup>
+    <Folder Include="Models\Samples\" />
+  </ItemGroup>
 </Project>

test/Microsoft.OpenApi.Tests/Models/OpenApiDocumentTests.cs

@@ -1,4 +1,4 @@
-// Copyright (c) Microsoft Corporation. All rights reserved.
+// Copyright (c) Microsoft Corporation. All rights reserved.
 // Licensed under the MIT license. 
 
 using System;
@@ -10,6 +10,7 @@
 using Microsoft.OpenApi.Extensions;
 using Microsoft.OpenApi.Interfaces;
 using Microsoft.OpenApi.Models;
+using Microsoft.OpenApi.Readers;
 using Microsoft.OpenApi.Writers;
 using VerifyXunit;
 using Xunit;
@@ -1314,5 +1315,32 @@ public void SerializeRelativeRootPathWithHostAsV2JsonWorks()
             actual.Should().Be(expected);
         }
 
+        [Fact]
+        public void TestHashCodesForSimilarOpenApiDocuments()
+        {
+            // Arrange
+            var sampleFolderPath = "Models/Samples/";            
+
+            var doc1 = ParseInputFile(Path.Combine(sampleFolderPath, "sampleDocument.yaml"));
+            var doc2 = ParseInputFile(Path.Combine(sampleFolderPath, "sampleDocument.yaml"));
+            var doc3 = ParseInputFile(Path.Combine(sampleFolderPath, "sampleDocumentWithWhiteSpaces.yaml"));
+
+            // Act && Assert
+            /*
+                Test whether reading in two similar documents yield the same hash code,
+                And reading in similar documents(one has a whitespace) yields the same hash code as the result is terse
+            */
+            Assert.True(doc1.HashCode != null && doc2.HashCode != null && doc1.HashCode.Equals(doc2.HashCode));
+            Assert.Equal(doc1.HashCode, doc3.HashCode);
+        }
+
+        private static OpenApiDocument ParseInputFile(string filePath)
+        {
+            // Read in the input yaml file
+            using FileStream stream = File.OpenRead(filePath);
+            var openApiDoc = new OpenApiStreamReader().Read(stream, out var diagnostic);
+
+            return openApiDoc;
+        }
     }
 }

test/Microsoft.OpenApi.Tests/Models/Samples/sampleDocument.yaml

@@ -0,0 +1,5 @@
+openapi : 3.0.0
+info:
+    title: Simple Document
+    version: 0.9.1
+paths: {}

test/Microsoft.OpenApi.Readers.Tests/V3Tests/Samples/OpenApiDocument/minimalDocumentWithWhitespace.yaml renamed to test/Microsoft.OpenApi.Tests/Models/Samples/sampleDocumentWithWhiteSpaces.yaml

@@ -1,9 +1,9 @@
 openapi : 3.0.0
+
 info:
     title: Simple Document
-    version: 0.9.1
 
-paths: {}
-
+    version: 0.9.1
 
+paths: {}