Shorten generated collection result names

eng/packages/http-client-csharp-mgmt/generator/Azure.Generator.Management/src/ManagementClientGenerator.cs

@@ -69,6 +69,7 @@ protected override void Configure()
             AddMetadataReference(MetadataReference.CreateFromFile(typeof(ArmClient).Assembly.Location));
             // renaming should come first
             AddVisitor(new NameVisitor());
+            AddVisitor(new CollectionResultNameVisitor());
             AddVisitor(new SerializationVisitor());
             AddVisitor(new RestClientVisitor());
             AddVisitor(new ResourceVisitor());

eng/packages/http-client-csharp-mgmt/generator/Azure.Generator.Management/src/Visitors/CollectionResultNameVisitor.cs

@@ -0,0 +1,67 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+
+using Microsoft.TypeSpec.Generator.ClientModel;
+using Microsoft.TypeSpec.Generator.Providers;
+using System;
+using System.Security.Cryptography;
+using System.Text;
+
+namespace Azure.Generator.Management.Visitors;
+
+internal class CollectionResultNameVisitor : ScmLibraryVisitor
+{
+    // Keep generated CollectionResults file names below the repo path-length budget
+    // even under long sdk\<service>\<package> prefixes.
+    internal const int MaxCollectionResultNameLength = 80;
+    private const int HashLength = 12;
+
+    private static readonly string[] _collectionResultSuffixes =
+    [
+        "AsyncCollectionResultOfT",
+        "CollectionResultOfT",
+        "AsyncCollectionResult",
+        "CollectionResult"
+    ];
+
+    protected override TypeProvider? VisitType(TypeProvider type)
+    {
+        if (type.CustomCodeView is null &&
+            type.Name.Length > MaxCollectionResultNameLength &&
+            TryGetCollectionResultSuffix(type.Name, out var suffix))
+        {
+            type.Update(name: BuildShortenedName(type.Name, suffix));
+        }
+
+        return type;
+    }
+
+    private static bool TryGetCollectionResultSuffix(string name, out string suffix)
+    {
+        foreach (var candidate in _collectionResultSuffixes)
+        {
+            if (name.EndsWith(candidate, StringComparison.Ordinal))
+            {
+                suffix = candidate;
+                return true;
+            }
+        }
+
+        suffix = string.Empty;
+        return false;
+    }
+
+    private static string BuildShortenedName(string originalName, string suffix)
+    {
+        var hash = GetStableHash(originalName);
+        var maxPrefixLength = MaxCollectionResultNameLength - suffix.Length - hash.Length;
+        var prefixLength = Math.Min(originalName.Length - suffix.Length, maxPrefixLength);
+        return $"{originalName[..prefixLength]}{hash}{suffix}";
+    }
+
+    private static string GetStableHash(string value)
+    {
+        var hash = SHA256.HashData(Encoding.UTF8.GetBytes(value));
+        return Convert.ToHexString(hash, 0, HashLength / 2);
+    }
+}

eng/packages/http-client-csharp-mgmt/generator/Azure.Generator.Management/test/CollectionResultNameVisitorTests.cs

@@ -0,0 +1,70 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+
+using System.Reflection;
+using Azure.Generator.Management.Tests.TestHelpers;
+using Azure.Generator.Management.Visitors;
+using Microsoft.TypeSpec.Generator;
+using Microsoft.TypeSpec.Generator.ClientModel;
+using Microsoft.TypeSpec.Generator.Providers;
+using NUnit.Framework;
+
+namespace Azure.Generator.Mgmt.Tests
+{
+    internal class CollectionResultNameVisitorTests
+    {
+        [Test]
+        public void RenamesLongCollectionResultType()
+        {
+            const string name = "MicrosoftCertificateRegistrationAppServiceCertificateOrdersRetrieveCertificateEmailHistoryAsyncCollectionResultOfT";
+            var type = new TestTypeProvider(name);
+
+            VisitType(type);
+
+            Assert.That(type.Name, Is.Not.EqualTo(name));
+            Assert.That(type.Name.Length, Is.LessThanOrEqualTo(CollectionResultNameVisitor.MaxCollectionResultNameLength));
+            Assert.That(type.Name, Does.EndWith("AsyncCollectionResultOfT"));
+        }
+
+        [Test]
+        public void KeepsShortCollectionResultType()
+        {
+            const string name = "FoosGetAllAsyncCollectionResultOfT";
+            var type = new TestTypeProvider(name);
+
+            VisitType(type);
+
+            Assert.That(type.Name, Is.EqualTo(name));
+        }
+
+        [Test]
+        public void KeepsLongNonCollectionResultType()
+        {
+            const string name = "MicrosoftCertificateRegistrationAppServiceCertificateOrdersRetrieveCertificateEmailHistoryModel";
+            var type = new TestTypeProvider(name);
+
+            VisitType(type);
+
+            Assert.That(type.Name, Is.EqualTo(name));
+        }
+
+        private static void VisitType(TypeProvider type)
+        {
+            ManagementMockHelpers.LoadMockPlugin();
+
+            var visitTypeCore = typeof(LibraryVisitor).GetMethod(
+                "VisitTypeCore",
+                BindingFlags.NonPublic | BindingFlags.Instance);
+            Assert.That(visitTypeCore, Is.Not.Null, "Could not find LibraryVisitor.VisitTypeCore method");
+
+            visitTypeCore!.Invoke(new CollectionResultNameVisitor(), [type]);
+        }
+
+        private class TestTypeProvider(string name) : TypeProvider
+        {
+            protected override string BuildName() => name;
+
+            protected override string BuildRelativeFilePath() => $"{Name}.cs";
+        }
+    }
+}

eng/packages/http-client-csharp-mgmt/generator/TestProjects/Local/Mgmt-TypeSpec/foo.tsp

@@ -145,6 +145,15 @@ interface Foos {
     ArmResponse<FooDependency[]>
   >;
 
+  @get
+  @action("retrieveCertificateEmailHistoryPathLengthRepro")
+  @clientName("GetPathLengthRepro")
+  microsoftCertificateRegistrationAppServiceCertificateOrdersRetrieveCertificateEmailHistoryPathLengthRepro is ArmResourceActionSync<
+    Foo,
+    void,
+    ArmResponse<FooDependency[]>
+  >;
+
   /** Get the provisioning state of a Foo resource. */
   @get
   @action("getProvisioningState")