Enforce maximum length in entity instance ids

Signed-off-by: Hal Spang <halspang@microsoft.com>

Author: halspang

src/Abstractions/Entities/EntityInstanceId.cs

@@ -28,6 +28,11 @@ public EntityInstanceId(string name, string key)
         Check.NotNull(key);
         this.Name = name.ToLowerInvariant();
         this.Key = key;
+
+        if (this.ToString().Length > 100)
+        {
+            throw new ArgumentException("entity instance ids may not exceed 100 characters in length.");
+        }
     }
 
     /// <summary>

test/Abstractions.Tests/Entities/EntityInstanceIdTests.cs

@@ -0,0 +1,55 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+using Microsoft.DurableTask.Entities;
+
+namespace Microsoft.DurableTask.Abstractions.Tests.Entities;
+
+public class EntityInstanceIdTests
+{
+    [Fact]
+    public void TestValidEntityInstanceId()
+    {
+        var entityId = new EntityInstanceId("entity", "key1");
+        Assert.Equal("@entity@key1", entityId.ToString());
+    }
+
+    [Fact]
+    public void TestEntityNameLowercased()
+    {
+        var entityId = new EntityInstanceId("Entity", "key1");
+        Assert.Equal("entity", entityId.Name);
+        Assert.Equal("@entity@key1", entityId.ToString());
+    }
+
+    [Fact]
+    public void TestEntityNameWithAtSymbolThrows()
+    {
+        Assert.Throws<ArgumentException>(() => new EntityInstanceId("entity@name", "key1"));
+    }
+
+    [Fact]
+    public void TestEntityInstanceIdExceedsMaxLengthThrows()
+    {
+        string longName = new string('a', 50);
+        string longKey = new string('b', 51);
+        Assert.Throws<ArgumentException>(() => new EntityInstanceId(longName, longKey));
+    }
+
+    [Fact]
+    public void TestFromStringValid()
+    {
+        var entityId = EntityInstanceId.FromString("@entity@key1");
+        Assert.Equal("entity", entityId.Name);
+        Assert.Equal("key1", entityId.Key);
+    }
+
+    [Fact]
+    public void TestFromStringInvalidThrows()
+    {
+        Assert.Throws<ArgumentException>(() => EntityInstanceId.FromString("invalid"));
+        Assert.Throws<ArgumentException>(() => EntityInstanceId.FromString("@entitykey1"));
+        Assert.Throws<ArgumentException>(() => EntityInstanceId.FromString("@@key1"));
+        Assert.Throws<ArgumentException>(() => EntityInstanceId.FromString($"@entity@{new string('a', 100)}"));
+    }
+}