From 636988a0727d01479f9af94ef1c56bb7e79ecb24 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Aleksey=20Kliger=20=28=CE=BBgeek=29?= <alklig@microsoft.com>
Date: Wed, 28 Apr 2021 12:02:13 -0400
Subject: [PATCH] Add AssemblyExtensions.GetApplyUpdateCapabilities method
 (#51954)

* Add AssemblyExtensions.GetApplyUpdateCapabilities method

* add linker descriptor

* fix whitespace

* assert result is a string
---
 .../Reflection/Metadata/AssemblyExtensions.cs      |  5 +++++
 .../src/ILLink/ILLink.Descriptors.Shared.xml       |  9 +++++++++
 .../tests/AssemblyExtensionsTest.cs                | 14 ++++++++++++++
 .../Reflection/Metadata/AssemblyExtensions.cs      | 11 ++++++-----
 4 files changed, 34 insertions(+), 5 deletions(-)

diff --git a/src/coreclr/System.Private.CoreLib/src/System/Reflection/Metadata/AssemblyExtensions.cs b/src/coreclr/System.Private.CoreLib/src/System/Reflection/Metadata/AssemblyExtensions.cs
index 28a4677d45eca..15ee7bd82bf61 100644
--- a/src/coreclr/System.Private.CoreLib/src/System/Reflection/Metadata/AssemblyExtensions.cs
+++ b/src/coreclr/System.Private.CoreLib/src/System/Reflection/Metadata/AssemblyExtensions.cs
@@ -81,5 +81,10 @@ public static void ApplyUpdate(Assembly assembly, ReadOnlySpan<byte> metadataDel
                 }
             }
         }
+
+        internal static string GetApplyUpdateCapabilities()
+        {
+            return "Baseline AddMethodToExistingType AddStaticFieldToExistingType AddInstanceFieldToExistingType NewTypeDefinition";
+        }
     }
 }
diff --git a/src/libraries/System.Private.CoreLib/src/ILLink/ILLink.Descriptors.Shared.xml b/src/libraries/System.Private.CoreLib/src/ILLink/ILLink.Descriptors.Shared.xml
index 3dfcceb59ebea..b70cb912600ec 100644
--- a/src/libraries/System.Private.CoreLib/src/ILLink/ILLink.Descriptors.Shared.xml
+++ b/src/libraries/System.Private.CoreLib/src/ILLink/ILLink.Descriptors.Shared.xml
@@ -62,4 +62,13 @@
       <method signature="System.Void Initialize()" />
     </type>
   </assembly>
+
+  <!-- methods used by hot reload.
+       TODO: once there's a feature flag, add it to the linker descriptor
+  -->
+  <assembly fullname="System.Private.CoreLib">
+    <type fullname="System.Reflection.Metadata.AssemblyExtensions">
+      <method name="GetApplyUpdateCapabilities" />
+    </type>
+  </assembly>
 </linker>
diff --git a/src/libraries/System.Runtime.Loader/tests/AssemblyExtensionsTest.cs b/src/libraries/System.Runtime.Loader/tests/AssemblyExtensionsTest.cs
index a1c7a4dd3111b..5208b573c75d2 100644
--- a/src/libraries/System.Runtime.Loader/tests/AssemblyExtensionsTest.cs
+++ b/src/libraries/System.Runtime.Loader/tests/AssemblyExtensionsTest.cs
@@ -30,5 +30,19 @@ public static void ApplyUpdateInvalidParameters()
             Assert.Throws<InvalidOperationException>(() =>
                 AssemblyExtensions.ApplyUpdate(typeof(AssemblyExtensions).Assembly, new ReadOnlySpan<byte>(metadataDelta), new ReadOnlySpan<byte>(ilDelta), ReadOnlySpan<byte>.Empty));
         }
+
+        [Fact]
+        public void GetApplyUpdateCapabilitiesIsCallable()
+        {
+            var ty = typeof(System.Reflection.Metadata.AssemblyExtensions);
+            var mi = ty.GetMethod("GetApplyUpdateCapabilities", BindingFlags.NonPublic | BindingFlags.Static, Array.Empty<Type>());
+
+            Assert.NotNull(mi);
+
+            var result = mi.Invoke(null, null);
+
+            Assert.NotNull(result);
+            Assert.Equal(typeof(string), result.GetType());
+        }
     }
 }
diff --git a/src/mono/System.Private.CoreLib/src/System/Reflection/Metadata/AssemblyExtensions.cs b/src/mono/System.Private.CoreLib/src/System/Reflection/Metadata/AssemblyExtensions.cs
index 337f1f516b1e6..471ab27922ed8 100644
--- a/src/mono/System.Private.CoreLib/src/System/Reflection/Metadata/AssemblyExtensions.cs
+++ b/src/mono/System.Private.CoreLib/src/System/Reflection/Metadata/AssemblyExtensions.cs
@@ -51,12 +51,13 @@ public static void ApplyUpdate(Assembly assembly, ReadOnlySpan<byte> metadataDel
 #endif
         }
 
-        internal static void ApplyUpdateSdb(Assembly assembly, byte[] metadataDelta, byte[] ilDelta, byte[]? pdbDelta)
+        internal static string GetApplyUpdateCapabilities()
         {
-            ReadOnlySpan<byte> md = metadataDelta;
-            ReadOnlySpan<byte> il = ilDelta;
-            ReadOnlySpan<byte> dpdb = pdbDelta == null ? default : pdbDelta;
-            ApplyUpdate (assembly, md, il, dpdb);
+#if !FEATURE_METADATA_UPDATE
+            return string.Empty;
+#else
+            return "Baseline";
+#endif
         }
 
 #if FEATURE_METADATA_UPDATE