[hot_reload] Don't look at delta method table rows

src/libraries/System.Runtime.Loader/tests/ApplyUpdate/System.Reflection.Metadata.ApplyUpdate.Test.FirstCallAfterUpdate/FirstCallAfterUpdate.cs

@@ -0,0 +1,12 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+namespace System.Reflection.Metadata.ApplyUpdate.Test
+{
+    public class FirstCallAfterUpdate {
+        public FirstCallAfterUpdate() {}
+        public string Method1 (string s) {
+            return s + " STRING";
+        }
+    }
+}

src/libraries/System.Runtime.Loader/tests/ApplyUpdate/System.Reflection.Metadata.ApplyUpdate.Test.FirstCallAfterUpdate/FirstCallAfterUpdate_v1.cs

@@ -0,0 +1,12 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+namespace System.Reflection.Metadata.ApplyUpdate.Test
+{
+    public class FirstCallAfterUpdate {
+        public FirstCallAfterUpdate() {}
+        public string Method1(string s) {
+            return "NEW " + s;
+        }
+    }
+}

src/libraries/System.Runtime.Loader/tests/ApplyUpdate/System.Reflection.Metadata.ApplyUpdate.Test.FirstCallAfterUpdate/FirstCallAfterUpdate_v2.cs

@@ -0,0 +1,12 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+namespace System.Reflection.Metadata.ApplyUpdate.Test
+{
+    public class FirstCallAfterUpdate {
+        public FirstCallAfterUpdate() {}
+        public string Method1(string s) {
+            return s + "EST STRING";
+        }
+    }
+}

src/libraries/System.Runtime.Loader/tests/ApplyUpdate/System.Reflection.Metadata.ApplyUpdate.Test.FirstCallAfterUpdate/System.Reflection.Metadata.ApplyUpdate.Test.FirstCallAfterUpdate.csproj

@@ -0,0 +1,12 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <RootNamespace>System.Runtime.Loader.Tests</RootNamespace>
+    <TargetFrameworks>$(NetCoreAppCurrent)</TargetFrameworks>
+    <TestRuntime>true</TestRuntime>
+    <DeltaScript>deltascript.json</DeltaScript>
+    <SkipTestUtilitiesReference>true</SkipTestUtilitiesReference>
+  </PropertyGroup>
+  <ItemGroup>
+    <Compile Include="FirstCallAfterUpdate.cs" />
+  </ItemGroup>
+</Project>

src/libraries/System.Runtime.Loader/tests/ApplyUpdate/System.Reflection.Metadata.ApplyUpdate.Test.FirstCallAfterUpdate/deltascript.json

@@ -0,0 +1,7 @@
+{
+    "changes": [
+        {"document": "FirstCallAfterUpdate.cs", "update": "FirstCallAfterUpdate_v1.cs"},
+       {"document": "FirstCallAfterUpdate.cs", "update": "FirstCallAfterUpdate_v2.cs"},
+    ]
+}
+

src/libraries/System.Runtime.Loader/tests/ApplyUpdateTest.cs

@@ -94,6 +94,26 @@ void LambdaCapturesThis()
             });
         }
 
+        [ConditionalFact(typeof(ApplyUpdateUtil), nameof (ApplyUpdateUtil.IsSupported))]
+        [ActiveIssue("https://github.com/dotnet/runtime/issues/54617", typeof(PlatformDetection), nameof(PlatformDetection.IsBrowser), nameof(PlatformDetection.IsMonoAOT))] 
+        void FirstCallAfterUpdate()
+        {
+            /* Tests that updating a method that has not been called before works correctly and that
+             * the JIT/interpreter doesn't have to rely on cached baseline data. */
+            ApplyUpdateUtil.TestCase(static () =>
+            {
+                var assm = typeof (ApplyUpdate.Test.FirstCallAfterUpdate).Assembly;
+
+                var o = new ApplyUpdate.Test.FirstCallAfterUpdate ();
+
+                ApplyUpdateUtil.ApplyUpdate(assm);
+                ApplyUpdateUtil.ApplyUpdate(assm);
+
+                string r = o.Method1("NEW");
+
+                Assert.Equal("NEWEST STRING", r);
+            });
+        }
 
         [ConditionalFact(typeof(ApplyUpdateUtil), nameof (ApplyUpdateUtil.IsSupported))]
         [ActiveIssue("https://github.com/dotnet/runtime/issues/52993", TestRuntimes.Mono)]

src/libraries/System.Runtime.Loader/tests/System.Runtime.Loader.Tests.csproj

@@ -38,6 +38,7 @@
     <ProjectReference Include="ApplyUpdate\System.Reflection.Metadata.ApplyUpdate.Test.CustomAttributeUpdate\System.Reflection.Metadata.ApplyUpdate.Test.CustomAttributeUpdate.csproj" />
     <ProjectReference Include="ApplyUpdate\System.Reflection.Metadata.ApplyUpdate.Test.LambdaBodyChange\System.Reflection.Metadata.ApplyUpdate.Test.LambdaBodyChange.csproj" />
     <ProjectReference Include="ApplyUpdate\System.Reflection.Metadata.ApplyUpdate.Test.LambdaCapturesThis\System.Reflection.Metadata.ApplyUpdate.Test.LambdaCapturesThis.csproj" />
+    <ProjectReference Include="ApplyUpdate\System.Reflection.Metadata.ApplyUpdate.Test.FirstCallAfterUpdate\System.Reflection.Metadata.ApplyUpdate.Test.FirstCallAfterUpdate.csproj" />
 
   </ItemGroup>
   <ItemGroup Condition="'$(TargetOS)' == 'Browser'">
@@ -54,6 +55,7 @@
       <TrimmerRootAssembly Condition="$([System.String]::Copy('%(ResolvedFileToPublish.FileName)%(ResolvedFileToPublish.Extension)').EndsWith('System.Reflection.Metadata.ApplyUpdate.Test.CustomAttributeUpdate.dll'))" Include="%(ResolvedFileToPublish.FullPath)" />
       <TrimmerRootAssembly Condition="$([System.String]::Copy('%(ResolvedFileToPublish.FileName)%(ResolvedFileToPublish.Extension)').EndsWith('System.Reflection.Metadata.ApplyUpdate.Test.LambdaBodyChange.dll'))" Include="%(ResolvedFileToPublish.FullPath)" />
       <TrimmerRootAssembly Condition="$([System.String]::Copy('%(ResolvedFileToPublish.FileName)%(ResolvedFileToPublish.Extension)').EndsWith('System.Reflection.Metadata.ApplyUpdate.Test.LambdaCapturesThis.dll'))" Include="%(ResolvedFileToPublish.FullPath)" />
+      <TrimmerRootAssembly Condition="$([System.String]::Copy('%(ResolvedFileToPublish.FileName)%(ResolvedFileToPublish.Extension)').EndsWith('System.Reflection.Metadata.ApplyUpdate.Test.FirstCallAfterUpdate.dll'))" Include="%(ResolvedFileToPublish.FullPath)" />
     </ItemGroup>
   </Target>
 

src/mono/mono/component/hot_reload.c

@@ -793,6 +793,13 @@ hot_reload_effective_table_slow (const MonoTableInfo **t, int *idx)
 	if (G_LIKELY (*idx < table_info_get_rows (*t) && !any_modified))
 		return;
 
+	/* FIXME: when adding methods this won't work anymore.  We will need to update the delta
+	 * images' suppressed columns (see the Note in pass2 about
+	 * CMiniMdRW::m_SuppressedDeltaColumns) with the baseline values. */
+	/* The only column from the updates that matters the RVA, which is looked up elsewhere. */
+	if (tbl_index == MONO_TABLE_METHOD)
+		return;
+
 	GList *list = info->delta_image;
 	MonoImage *dmeta;
 	int ridx;
@@ -1272,6 +1279,29 @@ apply_enclog_pass2 (MonoImage *image_base, BaselineInfo *base_info, uint32_t gen
 	MonoTableInfo *table_enclog = &image_dmeta->tables [MONO_TABLE_ENCLOG];
 	int rows = table_info_get_rows (table_enclog);
 
+	/* NOTE: Suppressed colums
+	 *
+	 * Certain column values in some tables in the deltas are not meant to be applied over the
+	 * previous generation. See CMiniMdRW::m_SuppressedDeltaColumns in CoreCLR.  For example the
+	 * MONO_METHOD_PARAMLIST column in MONO_TABLE_METHOD is always 0 in an update - for modified
+	 * rows the previous value must be carried over. For added rows, it is supposed to be
+	 * initialized to the end of the param table and updated with the "Param create" func code
+	 * in subsequent EnCLog records.
+	 *
+	 * For mono's immutable model (where we don't change the baseline image data), we will need
+	 * to mutate the delta image tables to incorporate the suppressed column values from the
+	 * previous generation.
+	 *
+	 * For Baseline capabilities, the only suppressed column is MONO_METHOD_PARAMLIST - which we
+	 * can ignore because we don't do anything with param updates and the only column we care
+	 * about is MONO_METHOD_RVA which gets special case treatment with set_update_method().
+	 *
+	 * But when we implement additional capabilities (for example UpdateParameters), we will
+	 * need to start mutating the delta image tables to pick up the suppressed column values.
+	 * Fortunately whether we get the delta from the debugger or from the runtime API, we always
+	 * have it in writable memory (and not mmap-ed pages), so we can rewrite the table values.
+	 */
+
 	gboolean assemblyref_updated = FALSE;
 	for (int i = 0; i < rows ; ++i) {
 		guint32 cols [MONO_ENCLOG_SIZE];